International guidelines for the management and treatment of Morquio A syndrome

Long-term outcomes of enzyme replacement therapy from a large cohort of Korean patients with mucopolysaccharidosis IVA (Morquio A syndrome)

Mucopolysaccharidosis (MPS) IVA (Morquio A syndrome) is an autosomal recessive lysosomal storage disorder caused by a mutation affecting the enzyme N-acetylgalactosamine-6-sulfatase (EC 3.1.6.4, GALNS). Enzyme replacement therapy (ERT) has been shown to improve physical performance, quality of life, and respiratory function in patients with MPS IVA; however, owing to the rarity of MPS IVA, data on Korean patient characteristics are limited. This retrospective study reports clinical, radiographic, biochemical, and molecular findings, and analyzes long-term clinical outcomes, from the largest cohort of Korean patients with MPS IVA in a single center. The analysis included 17 patients from 14 families (58.8 % females; median [range] age at diagnosis 5.2 [1.8-33.7] years). The majority of patients (64.7 %) were classified as having a severe phenotype, 23 % had an intermediate phenotype, and 11.8 % had an attenuated phenotype. Skeletal manifestations and radiologic abnormalities at initial diagnosis included gait abnormality (35.3 %), short stature (23.5 %), chest deformity (23.5 %), scoliosis (17.6 %), kyphosis (11.8 %), dysmorphic face (6 %), hip pain (6 %), and leg deformity (6 %). Twelve different GALNS mutations were identified. Patients received ERT for a median (range) 7.4 years (3.0-12.1). Twelve patients reached final adult height, and all patients with the severe/intermediate phenotype had short stature (<3rd percentile). Hemiepiphysiodesis was the most common surgical intervention among patients with the severe/intermediate phenotype. Drug-related adverse events (urticaria, rash, and anaphylaxis) were reported in four patients but were managed with antihistamines or desensitization. At follow-up, patients experienced improvements in functional independence measure score, ejection fraction, and the 6-min walk test compared with the pre-treatment baseline. This study provides real-world evidence for long-term stabilization of functional independence, endurance, and respiratory function among patients with MPS IVA treated with ERT, with no new safety concerns identified.

Prenatal Delivery of Enzyme Replacement Therapy to Fetuses Affected by Early-Onset Lysosomal Storage Diseases

The expansion of prenatal genetic screening and diagnosis warrants the evaluation of approved postnatal therapies that may be safely and feasibly translated to prenatal administration to a fetus affected by monogenic disease. For lysosomal storage diseases (LSDs), enzyme replacement therapy (ERT) often represents the main therapeutic approach. In utero enzyme replacement therapy (IUERT) has several potential benefits compared to postnatal therapy, such as: (1) delivering enzyme before the onset of irreversible organ damage; (2) developing tolerance toward the recombinant enzyme; and (3) targeting the central nervous system through a more permeable blood-brain barrier. In this review, we examine the general and disease-specific rationale for IUERT, and provide an overview of the main elements of our current clinical trial for the prenatal treatment of early-onset lysosomal storage diseases. Trial Registration: IUERT clinical trial: NCT04532047; Alpha thalassemia clinical trial: NCT02986698.

Hematopoietic stem cell transplantation in children with mucopolysaccharidosis IVA: single center experience

Mucopolysaccharidosis IVA (MPS IVA; Morquio syndrome) is a lysosomal storage disorder and features systemic skeletal dysplasia that is caused by defective Nacetylgalactosamine-6-sulfate sulfatase (GALNS). Although there are convincing data for hematopoietic stem cell transplantation (HSCT) in certain types of MPS, the studies are limited for MPS IVA and more data is still pending to show the efficacy/safety of HSCT. This study included 3 girls and 7 boys, with a median age of 75,5 months (35-186 months), who underwent allogeneic HSCT for severe MPS IVA between February 12, 2021, and March 10, 2023. Enzyme levels, height growth, the most involved organs (ear, eye, and heart), and the activities of daily living (ADL) scoring system were monitored to assess the benefit of HSCT. In a median follow-up of 20 months (9-34 months), there is no severe transplant-related adverse event was observed. In all cases, normal enzyme levels were reached after HSCT. During the short follow-up period, our cases showed an increase in stature and improvement in daily activity functions. Here we present the data of our HSCT experience in MPS IVA with promising results regarding both safety and efficacy. Although there are signs of amelioration with HSCT, we need more data and long-term follow-up to comment properly on the benefits of HSCT in MPS IVA.

Consensus-based expert recommendations on the management of MPS IVa and VI in Saudi Arabia

BACKGROUND

Mucopolysaccharidosis type IVa (Morquio A syndrome) and mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome) are rare inherited lysosomal storage diseases associated with significant functional impairment and a wide spectrum of debilitating clinical manifestations. These conditions are thought to have higher-than-average prevalence rates in Saudi Arabia due to high rates of consanguineous marriage in the country. There are several unmet needs associated with the management of these diseases in Saudi Arabia.

MAIN BODY

The aim of this manuscript is to contextualize unmet management needs and provide recommendations to optimize diagnosis, multidisciplinary care delivery, and local data generation in this disease area. An expert panel was assembled comprising seven consultant geneticists from across Saudi Arabia. The Delphi methodology was used to obtain a consensus on statements relating to several aspects of mucopolysaccharidosis types IVa and VI. A consensus was reached for all statements by means of an online, anonymized voting system. The consensus statements pertain to screening and diagnosis, management approaches, including recommendations pertaining to enzyme replacement therapy, and local data generation.

CONCLUSION

The consensus statements presented provide specific recommendations to improve diagnostic and treatment approaches, promote multidisciplinary care and data sharing, and optimize the overall management of these rare inherited diseases in Saudi Arabia.

Dental Profile of Brazilian Patients with Rare Skeletal Genetic Disorders: Clinical Features and Associated Factors

The aim of this study is to compare the dental profiles of Brazilian patients with rare genetic skeletal disorders and normotypical patients. A cross-sectional study was carried out with 210 individuals aged between 2 and 54 years old [105 with rare diseases (Mucopolysaccharidosis/MPS n = 27 and Osteogenesis Imperfecta/OI n = 78) and 105 without rare diseases] and their parents/caregivers. The parents/caregivers answered a questionnaire about individual aspects of their child and the dental profile was identified from questions related to dental history and the presence/absence of dental problems. The patients' oral cavity was also examined by three examiners for dental caries, malocclusion, gingivitis, and dental anomalies. The average age of individuals with a rare disease was 14.1 years (±12.2) and the median was 9.5 years. Participants who had already used the public health system (SUS) dental care services had a 2.24 times higher chance of belonging to the group with a rare disease (OR = 2.24; 95% CI: 1.07-4.89). Patients with rare diseases are 14.86 times more likely to have difficulty receiving dental treatment (OR = 14.86; 95% CI: 5.96-27.03) and 10.38 times more likely to have one or more dental problems (OR = 10.38; 95% CI: 1.95-35.17). Individuals with rare disorders have a greater history of difficulty in accessing dental treatment, using the SUS, and were diagnosed with more dental problems compared to normotypical individuals.

Hepatomegaly and Splenomegaly: An Approach to the Diagnosis of Lysosomal Storage Diseases

Clinical findings of hepatomegaly and splenomegaly, the abnormal enlargement of the liver and spleen, respectively, should prompt a broad differential diagnosis that includes metabolic, congestive, neoplastic, infectious, toxic, and inflammatory conditions. Among the metabolic diseases, lysosomal storage diseases (LSDs) are a group of rare and ultrarare conditions with a collective incidence of 1 in 5000 live births. LSDs are caused by genetic variants affecting the lysosomal enzymes, transporters, or integral membrane proteins. As a result, abnormal metabolites accumulate in the organelle, leading to dysfunction. Therapeutic advances, including early diagnosis and disease-targeted management, have improved the life expectancy and quality of life of people affected by certain LSDs. To access these new interventions, LSDs must be considered in patients presenting with hepatomegaly and splenomegaly throughout the lifespan. This review article navigates the diagnostic approach for individuals with hepatosplenomegaly particularly focusing on LSDs. We provide hints in the history, physical exam, laboratories, and imaging that may identify LSDs. Additionally, we discuss molecular testing, arguably the preferred confirmatory test (over biopsy), accompanied by enzymatic testing when feasible.

Post-tonsillectomy outcomes in children with mucopolysaccharidosis and obstructive sleep apnea

OBJECTIVE

To describe the incidence of respiratory complications, postoperative hemorrhage, length of stay, and cost of care in children with mucopolysaccharidosis (MPS) undergoing adenotonsillectomy (AT).

METHODS

Analysis of the 2009, 2012, and 2016 editions of the Healthcare Cost and Utilization Project Kids' Inpatient Database (HCUP KID) identified 24,700 children who underwent AT (40 children with MPS). Demographics, respiratory complications, postoperative hemorrhage, length of stay, and total cost were compared across children with and without MPS.

RESULTS

Children with MPS had a higher likelihood of being male (P < 0.017). There was a higher rate of respiratory complications in children with MPS compared with children without MPS [6/40 (15%) vs. 586/24,660 (2.4%), P < 0.001], which remained significant after adjusting for sex [adjusted odds ratio 6.88 (95% CI 2.87-16.46)]. There was also a higher risk of postoperative hemorrhage [4/40 (10%) vs. 444/24,660 (1.8%), P < 0.001), with sex-adjusted odds ratio of 5.97 (95% CI 2.12-16.86). Median (IQR) length of stay was increased in children with MPS (3 days, 1-4) compared with children without MPS (1 day, 1-2, P < 0.001). There was an increase in median (IQR) charges for hospital stay in children with MPS compared with their peers [$33,016 ($23,208.50-$72,280.50 vs. $15,383 ($9937-$24,462), P < 0.001].

CONCLUSIONS

Children with MPS undergoing AT had an increased risk of respiratory complications, postoperative hemorrhage, longer length of stay, and a higher cost of treatment when compared with children without MPS. This information may help inform interventional, perioperative, and postoperative decision making.

Molecular-based phenotype variations in amelogenesis imperfecta

Amelogenesis imperfecta (AI) is one of the typical dental genetic diseases in human. It can occur isolatedly or as part of a syndrome. Previous reports have mainly clarified the types and mechanisms of nonsyndromic AI. This review aimed to compare the phenotypic differences among the hereditary enamel defects with or without syndromes and their underlying pathogenic genes. We searched the articles in PubMed with different strategies or keywords including but not limited to amelogenesis imperfecta, enamel defects, hypoplastic/hypomaturation/hypocalcified, syndrome, or specific syndrome name. The articles with detailed clinical information about the enamel and other phenotypes and clear genetic background were used for the analysis. We totally summarized and compared enamel phenotypes of 18 nonsyndromic AI with 17 causative genes and 19 syndromic AI with 26 causative genes. According to the clinical features, radiographic or ultrastructural changes in enamel, the enamel defects were basically divided into hypoplastic and hypomineralized (hypomaturated and hypocalcified) and presented a higher heterogeneity which were closely related to the involved pathogenic genes, types of mutation, hereditary pattern, X chromosome inactivation, incomplete penetrance, and other mechanisms.The gene-specific enamel phenotypes could be an important indicator for diagnosing nonsyndromic and syndromic AI.

Clinical Characteristics of a Patient with Mucopolysaccharidosis Type IVA (Morquio Syndrome)

Mucopolysaccharidosis (MPS) type IVA (Morquio syndrome) is a hereditary lysosomal storage disease caused by deficiency of N-acetylglucosamine-6-sulfate sulfatase. This enzyme deficiency leads to specific glycosaminoglycans (keratan sulfate and chondroitin-6-sulfate) accumulation mainly in the bone and cartilage tissues, as well as in the cardiovascular, respiratory systems, and visual systems. Patients with MPS IVA look healthy at birth, however, they develop typical spine deformities (kyphoscoliosis), pectus carinatum, wrists hypermobility with decreased muscle strength and loss of fine motor skills, valgus deformation of lower limbs during the first years of life. Pathological changes in cardiovascular and respiratory systems, visual and acoustic analyzers can be revealed. Early diagnosis of the disease is crucial for timely initiation of enzyme replacement therapy. Thus, low incidence of the disease and its heterogeneous clinical picture complicates diagnosis. Consequently, patients with MAS IVA often become severely disabled as early as adolescence. Patients with severe form and without treatment die before the age of 30 due to complications of respiratory system diseases, valvular heart apparatus involvement, and cervical myelopathy.

Dental Considerations for the Treatment of Patients with Morquio Syndrome

Aim

Morquio syndrome, also called Mucopolysaccharidosis IV (MPS IV), is a rare autosomal recessive metabolic lysosomal disorder that results in the deposition of glycosaminoglycans (GAGs) in various tissues and organs, resulting in an array of signs and symptoms. The aim of the study was to systematically record the clinical features with a special emphasis on oral manifestations of patients diagnosed with MPS IV and asses the dental treatment implications of the disease manifestations.

Materials and methods

A cross-sectional study was conducted on patients diagnosed with MPS IV (n = 26). A complete clinical and oral examination was done and the findings were systemically recorded.

Results

The study showed that the patients diagnosed with MPS IV have multiple treatment challenges owing to the range of disease manifestations. Furthermore, they have higher oral health care needs because of the anatomical and pathological changes.

Conclusion and clinical significance

Dental professionals must be aware of the implications of the disease manifestation and their accompanying challenges while treating patients with MPS IV. The oral health needs are higher for these patients and regular dental evaluation and treatment must be incorporated into their health care regimen.

How to cite this article

Vinod A, Raj SN, Anand A, et al. Dental Considerations for the Treatment of Patients with Morquio Syndrome. Int J Clin Pediatr Dent 2022;15(6):707-710.

Efficacy of Intravenous Elosulfase Alfa for Mucopolysaccharidosis Type IVA: A Systematic Review and Meta-Analysis

Mucopolysaccharidosis type IVA (MPS IVA or Morquio A), a lysosomal storage disease with an autosomal recessive inherited pattern, is induced by GALNS gene mutations causing deficiency in N-acetylgalactosamine-6-sulfatase activity (GALNS; EC 3.1.6.4). Currently, intravenous (IV) enzyme replacement therapy (ERT) with elosulfase alfa is employed for treating MPS IVA patients. A systematic literature review was conducted to evaluate the efficacy and safety of IV elosulfase alfa for MPS IVA by searching the National Center for Biotechnology Information, U.S. National Library of Medicine National Institutes of Health (PubMed), Excerpta Medica dataBASE, and Cochrane Library databases, limited to clinical trials. Four cohort studies and two randomized controlled trials, with a total of 550 participants (327 on ERT treatment versus 223 on placebo treatment), satisfied the inclusion criteria. Pooled analysis of proportions and confidence intervals were also utilized to systematically review clinical cohort studies and trials. Per the pooled proportions analysis, the difference in means of urinary keratan sulfate (uKS), 6-min walk test, 3-min stair climb test, self-care MPS-Health Assessment Questionnaire, caregiver assistance and mobility, forced vital capacity, the first second of forced expiration, and maximal voluntary ventilation between the ERT and placebo treatment groups were -0.260, -0.102, -0.182, -0.360, -0.408, -0.587, -0.293, -0.311, and -0.213, respectively. Based on the currently available data, our meta-analysis showed that there is uKS, physical performance, quality of life, and respiratory function improvements with ERT in MPS IVA patients. It is optimal to start ERT after diagnosis.

Investigation of GALNS variants and genotype-phenotype correlations in a large cohort of patients with mucopolysaccharidosis type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a rare autosomal recessive disorder resulting from the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) caused by pathogenic variants in the GALNS gene. A systematic analysis for genotype-phenotype correlation is essential due to hundreds of variants generating different levels of residual GALNS activity and causing a wide degree of clinical manifestation effects. Here, we retrospectively analyzed clinical and genetic data of 108 unrelated patients with MPS IVA to investigate the variants spectrum of GALNS and assess their clinical effects. In this cohort, 82 patients were classified as severe, 14 as intermediate, and 12 as mild. One hundred and one GALNS variants were identified, of which 47 were novel. Most patients with at least one GALNS null variant were classified as severe phenotype (92%, 33/36). Missense variants mapped to different residues of GALNS protein resulted in different phenotypes in patients with MPS IVA. Ninety-two percent of patients with two missense variants mapped to buried residues were classified as severe (92%, 24/26), while at least one missense variant mapped to surface residues was identified in patients with biallelic missense variants presenting intermediate MPS IVA (78%, 7/9) and presenting mild MPS IVA (86%, 6/7). Our study contributes to a better understanding of the molecular spectrum of GALNS variants and their clinical implications. Based on the data herein reported, we generated a systematic flowchart correlating the GALNS variants to assist in phenotype prediction and classification of patients with MPS IVA.

The landscape of Mucopolysaccharidosis in Southern and Eastern European countries: a survey from 19 specialistic centers

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by defects in genes coding for different lysosomal enzymes which degrade glycosaminoglycans. Impaired lysosomal degradation causes cell dysfunction leading to progressive multiorgan involvement, disabling consequences and poor life expectancy. Enzyme replacement therapy (ERT) is now available for most MPS types, offering beneficial effects on disease progression and improving quality of life of patients. The landscape of MPS in Europe is not completely described and studies on availability of treatment show that ERT is not adequately implemented, particularly in Southern and Eastern Europe. In this study we performed a survey analysis in main specialist centers in Southern and Eastern European countries, to outline the picture of disease management in the region and understand ERT implementation. Since the considerable number of MPS IVA patients in the region, particularly adults, the study mainly focused on MPS IVA management and treatment.

Results

19 experts from 14 Southern and Eastern European countries in total responded to the survey. Results outlined a picture of MPS management in the region, with a high number of MPS patients managed in the centers and a high level of care. MPS II was the most prevalent followed by MPS IVA, with a particular high number of adult patients. The study particularly focused on management and treatment of MPS IVA patients. Adherence to current European Guidelines for follow-up of MPS IVA patients is generally adequate, although some important assessments are reported as difficult due to the lack of MPS skilled specialists. Availability of ERT in Southern and Eastern European countries is generally in line with other European regions, even though regulatory, organizational and reimbursement constrains are demanding.

Conclusions

The landscape of MPS in Southern and Eastern European countries is generally comparable to that of other European regions, regarding epidemiology, treatment accessibility and follow up difficulties. However, issues limiting ERT availability and reimbursement should be simplified, to start treatment as early as possible and make it available for more patients. Besides, educational programs dedicated to specialists should be implemented, particularly for pediatricians, clinical geneticists, surgeons, anesthesiologists and neurologists.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Recommended respiratory tests are not routinely performed for mucopolysaccharidosis patients

Mucopolysaccharidoses (MPS) are a group of rare genetic lysosomal storage disorders. The seven types of MPS exhibit a wide spectrum of clinical severity, including cognitive impairment, skeletal and joint abnormalities, short stature, coarsened facial features, vision loss, and cardiovascular and respiratory impairment, which are the leading causes of morbidity and mortality among MPS patients [1–3]. Ear, nose and throat (ENT) and upper airway manifestations are initially more pronounced, and may lead to the initial diagnosis. Lower airway disease becomes more frequent with increasing age. Symptoms can be tracheomalacia, stenosis and bronchomalacia. Bronchitis and pneumonia can appear, and are due to increased secretions and poor airway clearance. Restrictive lung disease predominates among patients with significant skeletal involvement, namely MPS-IV and MPS-VI. Sleep disturbances and obstructive sleep apnoea secondary to airway obstruction are common [4]. Specific therapy, such as enzyme replacement therapy (ERT), is available for most types of MPS.

Recommended respiratory tests used as major outcomes in clinical trials for MPS treatment cannot be routinely performed in everyday practice because neurocognitive impairment and motor skill difficulties affect compliance for most MPS patientshttps://bit.ly/3G4qp8U

Clinical Utility of Elosulfase Alfa in the Treatment of Morquio A Syndrome

Mucopolysaccharidosis type IVA (MPS IVA or Morquio A) is an autosomal recessive disorder and is one of the lysosomal storage diseases. Patients with MPS IVA have a striking skeletal phenotype but normal intellect. The phenotypic continuum of MPS IVA ranges from severe and rapid progress to mild and slow progress. The diagnosis of MPS IVA is usually suspected based on abnormal bone findings and dysplasia on physical examination and radiographic investigation in the preschool years. In the past, only supportive care was available. Due to the early and severe skeletal abnormalities, the orthopedic specialist was usually the main care provider. However, patients need aggressive monitoring and management of their systemic disease. Therefore, they need an interdisciplinary team for their care, comprising medical geneticists, cardiologists, pulmonary specialists, gastroenterologists, otolaryngologists, audiologists, and ophthalmologists. After the US Food and Drug Administration approved elosulfase alfa in 2014, patients older than 5 years could benefit from this treatment. Clinical trials showed clinically meaningful improvements with once-a-week intravenous dosing (2.0 mg/kg per week), significantly improving the 6min walk test, the 3min stair climb test, and respiratory function when compared with placebo. Elosulfase alfa is well-tolerated, and there is a good response indicated by decreasing urine glycosaminoglycans.

Clinical features and health-related quality of life in adult patients with mucopolysaccharidosis IVA: the Spanish experience

BACKGROUND

Mucopolysaccharidosis (MPS) IVA or Morquio A syndrome is a progressive and disabling disease characterized by a deficiency of the enzyme N-acetylgalactosamine-6-sulphate sulphatase. Its clinical presentation is very heterogeneous and poorly understood in adults. The aim of this study was to describe the clinical manifestations of MPS IVA in adult patients in Spain and to assess their health-related quality of life (HRQoL).

RESULTS

Thirty-three patients from nine reference centres participated in the study. The median age was 32 (interquartile range [IQR]: 20.5-40.5) years. The phenotype was classical in 54.5% of patients, intermediate in 33.3% of patients, and non-classical in 12.1% of patients. The most common clinical manifestation was bone dysplasia, with a median height of 118 (IQR: 106-136) cm. Other frequent clinical manifestations were hearing loss (75.7%), ligamentous laxity (72.7%), odontoid dysplasia (69.7%), limb deformities that required orthopaedic aids (mainly hip dysplasia and genu valgus) (63.6%), and corneal clouding (60.6%). In addition, 36.0% of patients had obstructive sleep apnoea/hypopnoea syndrome and 33.3% needed non-invasive ventilation. Cervical surgery and varisation osteotomy were the most common surgical interventions (36.4% each). Almost 80% of patients had mobility problems and 36.4% used a wheelchair at all times. Furthermore, 87.9% needed help with self-care, 33.3% were fully dependent, and 78.8% had some degree of pain. HRQoL according to the health assessment questionnaire was 1.43 (IQR: 1.03-2.00) in patients with the non-classical phenotype, but 2.5 (IQR: 1.68-3.00) in those with the classical phenotype. Seven patients were initiated on enzyme replacement therapy (ERT), but two of them were lost to follow-up. Lung function improved in four patients and slightly worsened in one patient. The distance achieved in the six-minute walk test increased in the four patients who could perform it. HRQoL was better in patients treated with elosulfase alfa, with a median (IQR) of 1.75 (1.25-2.34) versus 2.25 (1.62-3.00) in patients not treated with ERT.

CONCLUSIONS

The study provides real-world data on patients with MPS IVA. Limited mobility, difficulties with self-care, dependence, and pain were common, together with poor HRQoL. The severity and heterogeneity of clinical manifestations require the combined efforts of multidisciplinary teams.

Gene Therapy for Neuronopathic Mucopolysaccharidoses: State of the Art

The need for long-lasting and transformative therapies for mucopolysaccharidoses (MPS) cannot be understated. Currently, many forms of MPS lack a specific treatment and in other cases available therapies, such as enzyme replacement therapy (ERT), do not reach important areas such as the central nervous system (CNS). The advent of newborn screening procedures represents a major step forward in early identification and treatment of individuals with MPS. However, the treatment of brain disease in neuronopathic MPS has been a major challenge to date, mainly because the blood brain barrier (BBB) prevents penetration of the brain by large molecules, including enzymes. Over the last years several novel experimental therapies for neuronopathic MPS have been investigated. Gene therapy and gene editing constitute potentially curative treatments. However, despite recent progress in the field, several considerations should be taken into account. This review focuses on the state of the art of in vivo and ex vivo gene therapy-based approaches targeting the CNS in neuronopathic MPS, discusses clinical trials conducted to date, and provides a vision for the future implications of these therapies for the medical community. Recent advances in the field, as well as limitations relating to efficacy, potential toxicity, and immunogenicity, are also discussed.

Molecular basis of mucopolysaccharidosis IVA (Morquio A syndrome): A review and classification of GALNS gene variants and reporting of 68 novel variants

Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is a rare autosomal recessive lysosomal storage disorder caused by mutations in the N‐acetylgalactosamine‐6‐sulfatase (GALNS) gene. We collected, analyzed, and uniformly summarized all published GALNS gene variants, thus updating the previous mutation review (published in 2014). In addition, new variants were communicated by seven reference laboratories in Europe, the Middle East, Latin America, Asia, and the United States. All data were analyzed to determine common alleles, geographic distribution, level of homozygosity, and genotype‐phenotype correlation. Moreover, variants were classified according to their pathogenicity as suggested by ACMG. Including those previously published, we assembled 446 unique variants, among which 68 were novel, from 1190 subjects (including newborn screening positive subjects). Variants' distribution was missense (65.0%), followed by nonsense (8.1%), splicing (7.2%), small frameshift deletions(del)/insertions(ins) (7.0%), intronic (4.0%), and large del/ins and complex rearrangements (3.8%). Half (50.4%) of the subjects were homozygous, 37.1% were compound heterozygous, and 10.7% had only one variant detected. The novel variants underwent in silico analysis to evaluate their pathogenicity. All variants were submitted to ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/) to make them publicly available. Mutation updates are essential for the correct molecular diagnoses, genetic counseling, prenatal and preimplantation diagnosis, and disease management.

The combined prevalence of classified rare rheumatic diseases is almost double that of ankylosing spondylitis

BACKGROUND

Rare diseases (RDs) affect less than 5/10,000 people in Europe and fewer than 200,000 individuals in the United States. In rheumatology, RDs are heterogeneous and lack systemic classification. Clinical courses involve a variety of diverse symptoms, and patients may be misdiagnosed and not receive appropriate treatment. The objective of this study was to identify and classify some of the most important RDs in rheumatology. We also attempted to determine their combined prevalence to more precisely define this area of rheumatology and increase awareness of RDs in healthcare systems. We conducted a comprehensive literature search and analyzed each disease for the specified criteria, such as clinical symptoms, treatment regimens, prognoses, and point prevalences. If no epidemiological data were available, we estimated the prevalence as 1/1,000,000. The total point prevalence for all RDs in rheumatology was estimated as the sum of the individually determined prevalences.

RESULTS

A total of 76 syndromes and diseases were identified, including vasculitis/vasculopathy (n = 15), arthritis/arthropathy (n = 11), autoinflammatory syndromes (n = 11), myositis (n = 9), bone disorders (n = 11), connective tissue diseases (n = 8), overgrowth syndromes (n = 3), and others (n = 8). Out of the 76 diseases, 61 (80%) are classified as chronic, with a remitting-relapsing course in 27 cases (35%) upon adequate treatment. Another 34 (45%) diseases were predominantly progressive and difficult to control. Corticosteroids are a therapeutic option in 49 (64%) syndromes. Mortality is variable and could not be determined precisely. Epidemiological studies and prevalence data were available for 33 syndromes and diseases. For an additional eight diseases, only incidence data were accessible. The summed prevalence of all RDs was 28.8/10,000.

CONCLUSIONS

RDs in rheumatology are frequently chronic, progressive, and present variable symptoms. Treatment options are often restricted to corticosteroids, presumably because of the scarcity of randomized controlled trials. The estimated combined prevalence is significant and almost double that of ankylosing spondylitis (18/10,000). Thus, healthcare systems should assign RDs similar importance as any other common disease in rheumatology.

Plasma Proteomic Analysis in Morquio A Disease

Mucopolysaccharidosis type IVA (MPS IVA) is a lysosomal disease caused by mutations in the gene encoding the enzymeN-acetylgalactosamine-6-sulfate sulfatase (GALNS), and is characterized by systemic skeletal dysplasia due to excessive storage of keratan sulfate (KS) and chondroitin-6-sulfate in chondrocytes. Although improvements in the activity of daily living and endurance tests have been achieved with enzyme replacement therapy (ERT) with recombinant human GALNS, recovery of bone lesions and bone growth in MPS IVA has not been demonstrated to date. Moreover, no correlation has been described between therapeutic efficacy and urine levels of KS, which accumulates in MPS IVA patients. The objective of this study was to assess the validity of potential biomarkers proposed by other authors and to identify new biomarkers. To identify candidate biomarkers of this disease, we analyzed plasma samples from healthy controls (n=6) and from untreated (n=8) and ERT-treated (n=5, sampled before and after treatment) MPS IVA patients using both qualitative and quantitative proteomics analyses. The qualitative proteomics approach analyzed the proteomic profile of the different study groups. In the quantitative analysis, we identified/quantified 215 proteins after comparing healthy control untreated, ERT-treated MPSIVA patients. We selected a group of proteins that were dysregulated in MPS IVA patients. We identified four potential protein biomarkers, all of which may influence bone and cartilage metabolism: fetuin-A, vitronectin, alpha-1antitrypsin, and clusterin. Further studies of cartilage and bone samples from MPS IVA patients will be required to verify the validity of these proteins as potential biomarkers of MPS IVA.

Tracheal narrowing in children and adults with mucopolysaccharidosis type IVA: evaluation with computed tomography angiography

BACKGROUND

Mucopolysaccharidosis type IVA (MPS IVA) is characterized by progressive skeletal dysplasia and respiratory issues with difficult airway management during anesthesia.

OBJECTIVE

To characterize tracheal abnormalities in children and adults with MPS IVA including interplay of the trachea, vasculature, bones and thyroid at the thoracic inlet.

MATERIALS AND METHODS

Computed tomography (CT) angiograms of the chest were analyzed for trachea shape, narrowing and deviation at the thoracic inlet, course of vasculature, bone alignment and thyroid location. The tracheal cross-sectional area was measured at the cervical, thoracic inlet and intrathoracic levels.

RESULTS

Thirty-seven patients (mean age: 18.1 years) were included. The mean tracheal cross-sectional area narrowing at the thoracic inlet was 63.9% (range: -2.1-96%), with a trend for increased tracheal narrowing in older children. The trachea was commonly deviated rightward posterior (22/37, 59%). T- or W-shaped tracheas had two times greater tracheal narrowing than D- or U-shaped tracheas (P<0.05). The brachiocephalic artery was tortuous in 35/37 (95%) with direct impingement on the trachea in 24/37 (65%). No correlation was observed between bony thoracic inlet diameter and tracheal narrowing. The thyroid was located in the thoracic inlet in 28/37 (76%) cases, significantly associated with tracheal narrowing (P=0.016).

CONCLUSION

Narrowing, deviation and abnormal shape of the trachea at the thoracic inlet are common in children and adults with MPS IVA, with a trend toward increased narrowing with advancing age in children. A W- or T-shaped trachea is associated with focal tracheal narrowing. Crowding of the thoracic inlet, due to vascular tortuosity and thyroid position, appears to play a major role.

Disease burden, management patterns and multidisciplinary clinical approaches for patients with MPS IVA and VI in selected Latin American Countries

Background

There is a paucity of real-world epidemiological data on patients with mucopolysaccharidoses (MPS) in Latin America. This real-world study assessed the disease burden, management patterns and multidisciplinary clinical approaches for MPS-IVA and MPS-VI patients in Latin America (Colombia, Ecuador, Mexico, Peru).

Methods

Data were collected from physicians/specialists experienced in treating MPS patients between April–June 2020, via an online patient-diary survey.

Results

Overall, 29 physicians/specialists participated in this study. Data from 98 patients were analyzed (MPS-IVA, 71 patients and MPS-VI, 27 patients). Mean age for MPS-IVA patients was 17.5 years and for MPS-VI patients was 11.6 years, and the majority were females (52% and 78%, respectively). MPS-IVA and VI patients presented a high absenteeism from school (55% and 37%, respectively; <18 years age) and workplace (78% and 100%, respectively; >18 years age), indicating an impact of the disease on some aspects of the patients' quality of life. The onset of the first symptom occurred at the age of 3.1 years for MPS-IVA patients and at 1 year for MPS-VI, with delay in diagnosis (3.5–3.9 years from symptom onset) and enzyme replacement therapy (ERT) initiation (1.1–3.6 years from diagnosis). ERT interruptions were observed for MPS-IVA (48%) and MPS-VI patients (44%), with non-availability of medication recorded as the main reason for non-adherence (46% and 60% patients, respectively). ERT showed noticeable treatment benefits in MPS-IVA/VI patients, with stabilization/reduction in complications or the number of surgeries. A multidisciplinary clinical team approach was used for patient management.

Conclusion

The disease burden for MPS-IVA/VI was high in Latin America, with consistent management, treatment and socio-demographic trends throughout the region.

Pectus carinatum as the key to early diagnosis of Morquio A syndrome: a case report

Background

A 20-month-old Asian boy with normal growth presented with genu valgum, kyphosis, and pectus carinatum, with no neurological symptoms. No other symptoms suggestive of mucopolysaccharidoses, for example joint contracture and peculiar facies, were present.

Case presentation

As part of our differential diagnosis we found elevated urine glycosaminoglycans, which triggered further investigation. Detailed examination showed flattening of the ribs, kyphoscoliosis and ovalization of the thoracolumbar vertebral body, strikingly short metacarpals, and very slight cardiac regurgitation. N-Acetylgalactosamine-6-sulfatase levels in the blood and dermal fibroblasts were very low, thus confirming diagnosis of Morquio A within 2 months of presentation. The patient was placed on elosulfase alfa enzyme replacement therapy and followed for 3 years.

Conclusions

This case exemplifies the importance of considering mucopolysaccharidoses as part of the initial differential diagnosis of pediatric patients with skeletal deformities; urine glycosaminoglycan levels and a blood enzyme mucopolysaccharidoses panel are simple screening tests that could lead to early definitive diagnosis.

Occurrence of Inborn Errors of Metabolism in Newborns, Diagnosis and Prophylaxis

Inborn errors of metabolism (IEM) are a heterogeneous group of rare genetic disorders that are generally transmitted as autosomal or X-linked recessive disorders. These defects arise due to mutations associated with specific gene(s), especially the ones associated with key metabolic enzymes. These enzymes or their product(s) are involved in various metabolic pathways, leading to the accumulation of intermediary metabolite(s), reflecting their toxic effects upon mutations. The diagnosis of these metabolic disorders is based on the biochemical analysis of the clinical manifestations produced and their molecular mechanism. Therefore, it is imperative to devise diagnostic tests with high sensitivity and specificity for early detection of IEM. Recent advances in biochemical and polymerase chain reaction-based genetic analysis along with pedigree and prenatal diagnosis can be life-saving in nature. The latest development in exome sequencing for rapid diagnosis and enzyme replacement therapy would facilitate the successful treatment of these metabolic disorders in the future. However, the longterm clinical implications of these genetic manipulations is still a matter of debate among intellectuals and requires further research.

Characterization of New Proteomic Biomarker Candidates in Mucopolysaccharidosis Type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a lysosomal storage disease caused by mutations in the N-acetylgalactosamine-6-sulfatase (GALNS) gene. Skeletal dysplasia and the related clinical features of MPS IVA are caused by disruption of the cartilage and its extracellular matrix, leading to a growth imbalance. Enzyme replacement therapy (ERT) with recombinant human GALNS has yielded positive results in activity of daily living and endurance tests. However, no data have demonstrated improvements in bone lesions and bone grow thin MPS IVA after ERT, and there is no correlation between therapeutic efficacy and urine levels of keratan sulfate, which accumulates in MPS IVA patients. Using qualitative and quantitative proteomics approaches, we analyzed leukocyte samples from healthy controls (n = 6) and from untreated (n = 5) and ERT-treated (n = 8, sampled before and after treatment) MPS IVA patients to identify potential biomarkers of disease. Out of 690 proteins identified in leukocytes, we selected a group of proteins that were dysregulated in MPS IVA patients with ERT. From these, we identified four potential protein biomarkers, all of which may influence bone and cartilage metabolism: lactotransferrin, coronin 1A, neutral alpha-glucosidase AB, and vitronectin. Further studies of cartilage and bone alterations in MPS IVA will be required to verify the validity of these proteins as potential biomarkers of MPS IVA.

Clinical outcomes in elderly patients with Morquio a syndrome receiving enzyme replacement therapy - experience in a Colombian center

INTRODUCTION

Mucopolysaccharidosis type IV A (MPS IVA) or Morquio A syndrome is an autosomal recessive lysosomal storage disease caused by GALNS gene mutations that lead to a deficiency of the N-acetylgalactosamine-6-sulfate sulfatase enzyme and the accumulation of two glycosaminoglycans in cell lysosomes, namely, chondroitin and keratan sulfate.

OBJECTIVE

To present two female patients with Morquio A syndrome in their late adult years (over 50 years of age) with a classical phenotype, treated with enzyme replacement therapy; and to present a summary of the natural history and the characteristics of the disease, and the benefit of comprehensive management.

MATERIALS AND METHODS

Descriptive clinical study before and after the treatment with enzyme replacement therapy as part of the comprehensive management of MPS IVA.

RESULTS

Enzyme replacement therapy with elosulfase alfa was effective, with an adequate safety profile in these two patients, showing evidence of sustained improvement in terms of endurance and gait patterns.

CONCLUSION

We present two cases of MPS IVA, with longer survival than reported previously in classical phenotypes associated with this disease condition. There is a paucity of reports of similar cases in the literature. We believe that the clinical heterogeneity of the disease manifesting with the classical phenotype, together with comprehensive management, have played a role in the survival of these two patients. Therapy with elosulfase alfa as part of comprehensive management has been crucial; we suspect a clinical response and infer a better quality of life and reduced burden for the caregiver, supporting its use in older patients.

Clinical characteristics of patients from Quebec, Canada, with Morquio A syndrome: a longitudinal observational study

Background

Morquio A syndrome is a rare, autosomal recessive, progressively debilitating disorder, with multi-system impairments and high medical burden. Quebec, Canada has a large Morquio A population, which is considered unique due to the presence of founder pathogenic variants. The objectives of this study were to document the genetic and clinical heterogeneity of patients with Morquio A in Quebec, to better characterize the phenotype of those with the French Canadian founder pathogenic variant (NM_000512.5: c.1171A>G, p.Met391Val), and to describe the natural history of the patients treated with elosulfase alfa enzyme replacement therapy. Patients with Morquio A were genotyped for pathogenic variants in the lysosomal enzyme N-acetylgalactosamine-6-sulfatase. Clinical data were retrospectively collected from medical charts of patients and included medical history, height, physical examination, respiratory function tests, electrocardiogram, echocardiogram, endurance in the 6-min walk test (6MWT), and activities of daily living (ADL) as assessed by the Mucopolysaccharidosis Health Assessment Questionnaire (MPS-HAQ). Longitudinal data were collected retrospectively and prospectively for patients treated with elosulfase alfa.

Results

A total of 33 patients, aged 5–63 years, were included in the analysis. Patients with the founder pathogenic variant (n = 17) generally exhibited a non-classical form of Morquio A. As compared with patients with a non-founder pathogenic variant (n = 16), these patients were generally taller, had greater endurance and were better able to perform ADL. However, they still had significant musculoskeletal disease. Most of the 26 patients treated with elosulfase alfa, regardless of pathogenic variant, showed improvements in endurance and ADL. After 5 to 12 months of treatment, the mean improvement from baseline in the 6MWT was 23% and 10 of 14 patients improved in at least one MPS-HAQ domain. Endurance and ADL generally continued to improve or maintained stable in the long term (up to 7 years). Four out of 19 treated patients with echocardiogram data at follow-up showed progression of cardiac disease.

Conclusions

In Quebec, Canada, Morquio A frequently manifests as a non-classical form of the syndrome due to a founder effect. Patients treated with elosulfase alfa generally show long-term improvement or stability in endurance and function, regardless of pathogenic variant.

Hearing Loss in Mucopolysaccharidoses: Current Knowledge and Future Directions

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by a deficiency of one of the enzymes involved in the degradation of glycosaminoglycans. Hearing loss is a common clinical presentation in MPS. This paper reviews the literature on hearing loss for each of the seven recognized subtypes of MPS. Hearing loss was found to be common in MPS I, II, III, IVA, VI, and VII, and absent from MPS IVB and MPS IX. MPS VI presents primarily with conductive hearing loss, while the other subtypes (MPS I, MPS II, MPS III, MPS IVA, and MPS VII) can present with any type of hearing loss (conductive, sensorineural, or mixed hearing loss). The sensorineural component develops as the disease progresses, but there is no consensus on the etiology of the sensorineural component. Enzyme replacement therapy (ERT) is the most common therapy utilized for MPS, but the effects of ERT on hearing function have been inconclusive. This review highlights a need for more comprehensive and multidisciplinary research on hearing function that includes behavioral testing, objective testing, and temporal bone imaging. This information would allow for better understanding of the progression and etiology of hearing loss. Owing to the prevalence of hearing loss in MPS, early diagnosis of hearing loss and annual comprehensive audiological evaluations are recommended.

Critical clinical situations in adult patients with Mucopolysaccharidoses (MPS)

Background

Mucopolysaccharidoses (MPS) are rare, inherited disorders associated with enzyme deficiencies that result in glycosaminoglycan (GAG) accumulation in multiple organ systems. Management of MPS is evolving as patients increasingly survive to adulthood and undergo multiple surgeries throughout their lives. As surgeries in these patients are considered to be high risk, this can result in a range of critical clinical situations in adult patients.

Results

We discuss strategies to prepare for and manage critical clinical situations in adult patients with MPS, including supporting the multidisciplinary team, preoperative and airway assessments, surgical preparations, and postoperative care. We also present eight critical clinical cases (age range: 21–38 years) from four leading inherited metabolic disease centres in Europe to highlight challenges and practical solutions to optimise the care of adult patients with MPS. Critical clinical situations included surgical procedures, pregnancy and a thrombus in a port-a-cath.

Conclusions

Individualised strategies to manage critical clinical situations need to be developed for each patient to compensate for the heterogeneous symptoms that may be present and the potential complications that may occur. These strategies should include input from the wider MDT, and be coordinated by metabolic specialists with expertise in the management of MPS disorders and surgery in adult patients with MPS.

Pathophysiology of Hip Disorders in Patients with Mucopolysaccharidosis IVA

Patients with mucopolysaccharidoses IVA (MPS IVA) have a progressive accumulation of the specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS), leading to the degeneration of the cartilage matrix and its connective tissue perturbing the regular microarchitecture of cartilage and successively distorting bone ossification and growth. Impaired cartilage quality and poor bone mineralization lead to serious hip disorders in MPS IVA patients. Although hip dysplasia is seen widely in musculoskeletal abnormality of this disorder, the pathophysiology of the hip bone and cartilage morphology in these patients remains unclear. Until now, no systemic study of the hip joints in MPS IVA has been reported by using the combined images of plain film radiographs (PFR) and Magnetic Resonance Imaging (MRI). This study aimed to assess the bony and cartilaginous features of hip joints and to explore the potentially related factors of femoral head osteonecrosis (FHN) and hip subluxation/dislocation in patients with MPS IVA. Hip joints in MPS IVA patients were retrospectively reviewed, based on the findings of PFR and MRI data from 2014 to 2019. Demographic information was also collected and analyzed with imaging measurements. A total of 19 patients (eight boys and 11 girls) were recruited, and 38 hip joints in these patients were examined. Eleven patients (57.9%) had FHN. FHN patients were statistically compared with those without FHN. Correlations between cartilaginous femoral head coverage (CFHC) and acetabular index (AI), cartilaginous AI (CAI), or neck-shaft angle (NSA) were investigated in patients with hip subluxation or dislocation. The greater cartilaginous coverage of the hips than their osseous inherency was observed. Significant correlation was observed between CFHC and AI (r =-0.351, p = 0.049) or CAI (r =-0.381, p = 0.032). Severe subluxations or dislocations were more likely to be present in those with more dysplastic bony and cartilaginous hips. In conclusion, our study provides the first systemic description of bony and cartilaginous characteristics in the hip morphology of MPS IVA patients. We have demonstrated that plain radiography alone leads to a misunderstanding of hip morphology and that MRI measurements with PFR are an essential tool to evaluate the 'true' characterization of hips for MPS IVA patients.

Assessing the impact of the five senses on quality of life in mucopolysaccharidoses

Background

The mucopolysaccharidoses (MPSs) are lysosomal storage disorders associated with progressive multi-organ and skeletal abnormalities. Clinical manifestations can affect each of the five senses: hearing, vision, smell, taste, and touch.

Main body of the abstract

On 24–26 May 2018, 46 specialists with expertise in managing symptoms of MPS and experts specialized in evaluating and managing impairments in each one of the five senses gathered in Lisbon, Portugal at the “MPS & the five senses” meeting to discuss how loss of one or multiple senses can affect activities of daily living (ADL) and quality of life (QoL) in MPS patients and best practices in evaluating and managing the loss of senses in these individuals. The meeting confirmed that MPS can affect the senses considerably, but how these impairments affect ADL and overall QoL from a patient’s perspective remains unclear. A better insight may be achieved by prospectively collecting patient-reported outcome (PRO) data internationally in a standardized way, using a standard battery of tools. To identify relevant PRO tools, a systematic literature review and a selection of existing published questionnaires, focused on adults with no intellectual delay, were performed after the meeting. The search strategy identified 33 PRO tools for hearing, 30 for speech, 125 for vision, 49 for touch (including pain and upper limb function), and 15 for smell/taste. A further selection was made based on several criteria, including applicability/relevance for MPS, applicability in different countries (languages)/cultures, availability in English, ease of use, validation, and normative data, resulting in a final set of 11 tools. In addition to these sense-specific PRO tools, a general QoL tool, the EuroQol (EQ)-5D-5 L, was selected to assess overall QoL and reveal coping behaviors.

Short conclusion

MPS can affect each of the five senses, but current knowledge on the impact of sense impairments on QoL/ADL in MPS patients remains limited. Collection of data in a standardized fashion using sense-specific patient-reported outcome tools and a general QoL tool may fill the current knowledge gap.

Abnormally increased carotid intima media-thickness and elasticity in patients with Morquio A disease

Background

Cardiovascular disease frequently causes morbidity and mortality in mucopolysaccharidoses (MPS); however, cardiovascular anatomy and dysfunction in MPS IVA (Morquio A disease) is not well described. Consequently, the study aimed to compare carotid artery structure and elasticity of MPS IVA patients with other MPS patients and healthy control subjects, and quantitate frequency of MPS IVA cardiac structural and functional abnormalities.

Methods

Prospective, multi-center echocardiogram and carotid ultrasound evaluations of 12 Morquio A patients were compared with other MPS and healthy control subjects. Average differences between groups were adjusted for age, sex, and height with robust variance estimation for confidence intervals and P-values.

Results

Morquio A patients demonstrated significantly higher (P < 0.001) adjusted carotid intima-media thickness (cIMT), mean (SD) of 0.56 mm (0.03) compared to control subjects, 0.44 mm (0.04). The Morquio A cohort had significantly greater adjusted carotid elasticity (carotid cross-sectional compliance + 43%, P < 0.001; carotid incremental elastic modulus − 33%, P = 0.003) than control subjects and other MPS patients. Aortic root dilatation was noted in 56% of the Morquio A cohort, which also had highly prevalent mitral (73%) and aortic (82%) valve thickening, though hemodynamically significant valve dysfunction was less frequent (9%).

Conclusions

Increased carotid elasticity in Morquio A patients is an unexpected contrast to the reduced elasticity observed in other MPS. These Morquio A cIMT findings corroborate MPS IVA arterial post-mortem reports and are consistent with cIMT of other MPS. Aortic root dilatation in Morquio A indicates arterial elastin dysfunction, but their carotid hyperelasticity indicates other vascular intima/media components, such as proteoglycans, may also influence artery function. Studying MPS I and IVA model systems may uniquely illuminate the function of glycosaminoglycan-bearing proteoglycans in arterial health.

A perspective on research, diagnosis, and management of lysosomal storage disorders in Colombia

Lysosomal storage diseases (LSDs) are a group of about 50 inborn errors of metabolism characterized by the lysosomal accumulation of partially or non-degraded molecules due to mutations in proteins involved in the degradation of macromolecules, transport, lysosomal biogenesis or modulators of lysosomal environment. Significant advances have been achieved in the diagnosis, management, and treatment of LSDs patients. In terms of approved therapies, these include enzyme replacement therapy (ERT), substrate reduction therapy, hematopoietic stem cell transplantation, and pharmacological chaperone therapy. In this review, we summarize the Colombian experience in LSDs thorough the evidence published. We identified 113 articles published between 1995 and 2019 that included Colombian researchers or physicians, and which were mainly focused in Mucopolysaccharidoses, Pompe disease, Gaucher disease, Fabry disease, and Tay-Sachs and Sandhoff diseases. Most of these articles focused on basic research, clinical cases, and mutation reports. Noteworthy, implementation of the enzyme assay in dried blood samples, led to a 5-fold increase in the identification of LSD patients, suggesting that these disorders still remain undiagnosed in the country. We consider that the information presented in this review will contribute to the knowledge of a broad spectrum of LSDs in Colombia and will also contribute to the development of public policies and the identification of research opportunities.

Mucopolysaccharidosis IVA: Diagnosis, Treatment, and Management

Mucopolysaccharidosis type IVA (MPS IVA, or Morquio syndrome type A) is an inherited metabolic lysosomal disease caused by the deficiency of the N-acetylglucosamine-6-sulfate sulfatase enzyme. The deficiency of this enzyme accumulates the specific glycosaminoglycans (GAG), keratan sulfate, and chondroitin-6-sulfate mainly in bone, cartilage, and its extracellular matrix. GAG accumulation in these lesions leads to unique skeletal dysplasia in MPS IVA patients. Clinical, radiographic, and biochemical tests are needed to complete the diagnosis of MPS IVA since some clinical characteristics in MPS IVA are overlapped with other disorders. Early and accurate diagnosis is vital to optimizing patient management, which provides a better quality of life and prolonged life-time in MPS IVA patients. Currently, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are available for patients with MPS IVA. However, ERT and HSCT do not have enough impact on bone and cartilage lesions in patients with MPS IVA. Penetrating the deficient enzyme into an avascular lesion remains an unmet challenge, and several innovative therapies are under development in a preclinical study. In this review article, we comprehensively describe the current diagnosis, treatment, and management for MPS IVA. We also illustrate developing future therapies focused on the improvement of skeletal dysplasia in MPS IVA.

Modeling Morquio A Syndrome: An Anthropometric Study of Body Characteristics and Stature

BACKGROUND

Morquio A syndrome or mucopolysaccharidosis (MPS) IVA is an autosomal recessive, life-limiting lysosomal storage disease caused by deficient activity of the enzyme galactosamine-6-sulfatase. Common early symptoms such as abnormalities of body stature can facilitate timely diagnosis. This study aimed to create a pattern of face and body stature based on anthropometric measurements taken from a cohort of Polish patients with MPS IVA.

METHODS

Analysis of 11 somatometric and 14 craniofacial features was performed on 20 patients with MPS IVA, aged from 3 months to 26 years. The diagnosis of MPS IVA was confirmed by enzymatic and molecular analysis. Two-tailed t-tests were used to compare mean values for body length and weight at birth between the MPS IVA patients and the general population. To show the degree and direction of deviation z-scores were calculated and then used to construct a model of an average MPS IVA patient.

RESULTS

Mean values for body height and weight at birth were greater for boys than for the general population. The observed pattern of head and body shape indicated that dwarfism occurred with age as a result of the relatively short trunk and lower limbs. Skeletal abnormalities included a bell-shaped chest with the ratio of chest depth to chest width being significantly above the norm. The head and neck were relatively elongated, in comparison to body height, and tucked between narrow shoulders. The head had dolichocephalic shape, while the nose was short with wide nostrils.

CONCLUSIONS

Multiple anthropometric measurements, including age ranges, allowed for the creation of a model that showed the most characteristic features of the MPS IVA phenotype.

MRI findings of the cervical spine in patients with mucopolysaccharidosis type VI: relationship with neurological physical examination

AIM

To describe the magnetic resonance imaging (MRI) findings of the cervical spine of patients with mucopolysaccharidosis type VI (MPS VI) and correlate them with clinical manifestations.

MATERIALS AND METHODS

This is a cross-sectional study involving 12 patients with MPS VI. A limited neurological examination was undertaken in each patient including Tinel's test, assessment of muscle tone, and the evaluation of deep tendon reflexes. Additionally, each patient underwent cervical spine MRI to evaluate platybasia, odontoid dysplasia, periodontoid soft-tissue thickening, spinal canal stenosis, myelopathy, basilar invagination, platyspondyly, and reduction of nasopharyngeal airway.

RESULTS

Nine patients were male (75%). The average age was 12.5 (±3.5 years). Tinel's test was negative in all patients. No muscle tone abnormalities were observed. Approximately 48% of the tested reflexes were considered abnormal, 10 of which (8.3%) were pathological occurring in five different patients (41.6%). At MRI, all patients showed periodontoid soft-tissue thickening and cervical spinal stenosis; six showed spinal cord compression and two showed myelopathy. Odontoid hypoplasia and basilar invagination were observed in nine patients. All patients with cervical stenosis on MRI had abnormal reflexes; however, only two of the six patients with evidence of cord compression on MRI had abnormal reflexes on clinical examination.

CONCLUSIONS

The present study of 12 patients with MPS VI demonstrated that a normal neurological examination cannot confidently exclude potential cord compression in patients with this condition. MRI may aid in the timely identification of cervical spine abnormalities, and potentially play a role in lessening morbidity and mortality in patients with MPS.

Long-Term Outcomes of Early Enzyme Replacement Therapy for Mucopolysaccharidosis IV: Clinical Case Studies of Two Siblings

Enzyme replacement therapy (ERT) is one of the available therapies for mucopolysaccharidosis (MPS). This study presents a follow-up of two siblings with MPS IVA (Morquio A disease) that received ERT. Both siblings received weekly intravenous infusions of elosulfase alfa for 4.5 years. One sibling (patient 1, P1; male) started therapy at 54 months of age, and the other sibling (patient 2, P2; female) started at 11 months of age. ERT was well-tolerated. In comparison to P1, P2’s growth curves deviated less from the norm. The orthopedic deformities of P1 were more severe than those of P2 and required several surgical corrections. P1’s sleep test at 48 months revealed obstructive sleep apnea, while by the age of 102 months, parameters were normal. P2 never had sleep apnea. Only P1 demonstrated ear, nose, and throat clinical illnesses. In comparison to P1, P2’s physical function was better maintained. In conclusion, ERT was safe in both patients during a 4.5-year follow-up. Although the typical characteristics of this disease were similar in both patients, P1 had a complex clinical course in comparison to P2, which influenced function and quality of life. Therefore, in order to make the most of ERT, it may be more beneficial when initiated at a relatively young age.

Newborn screening for mucopolysaccharidoses: Measurement of glycosaminoglycans by LC-MS/MS

Mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders which can lead to degenerative and irreversible skeletal, cardiovascular, pulmonary, and neurological damage. Current treatments, including hematopoietic stem cell transplantation and enzyme replacement therapy, have been found most effective if administered before clinical symptoms are present, highlighting the urgent need for the development of newborn screening.

This study analyzed 18,222 dried blood spot samples from newborns for both enzyme activity and glycosaminoglycan (GAG) concentration levels. GAG levels were measured using liquid chromatography tandem mass spectrometry. Results were compared to our previously established cutoff values for three subtypes of GAGs: dermatan sulfate (DS) and heparan sulfate (HS0S and HSNS). Samples that were high for two of the three GAGs were identified and screened a second time. Samples were also measured for iduronate-2-sulfatase and alfa-L-iduronidase activity.

A total of 300 samples were above the established cutoff values for at least two of the three GAGs after the first screening. One sample was determined through clinical and genetic testing to be a true positive for MPS II. The false positive rate after the first GAG screening was 1.64%. A Cochran's formula test showed that the samples available for the second screening were representative samples (p = .0000601). False positive rate after second GAG screening, extrapolated from the representative sample was 0.4%. False positive rate after enzyme activity assay by fluorimetry for IDUA and IDS enzymes was 0.21% and 0.18%. A combination of GAG and enzyme assays provided no false positive and false negative samples.

Two-tier screening involving a combination of enzyme activity and multiple GAGs should be considered the gold standard for the diagnosis of MPS patients.

Coordinated approach to spinal and tracheal reconstruction in a patient with morquio syndrome

Morquio syndrome (Mucopolysaccharidosis IVA) is an autosomal recessive lysosomal storage disease with manifestations ranging from mild to severe phenotype. Mechanical spinal cord injury and airway insufficiency are major causes of mortality. A 17-year-old male patient with severe Morquio syndrome presented with cervical and upper thoracic spinal stenosis with spinal cord myelopathy, and progressive severe tracheal stenosis. Coordinated care among otolaryngology, orthopedic surgery, neurosurgery, anesthesiology, cardiovascular surgery, radiology, and pulmonology teams facilitated the successful planning and execution of two major surgical interventions in rapid succession. This is the first description of a successful coordinated spine and airway repair in the literature.

Transition of patients with mucopolysaccharidosis from paediatric to adult care

Mucopolysaccharidoses (MPS) are rare disorders associated with enzyme deficiencies, resulting in glycosaminoglycan (GAG) accumulation in multiple organ systems. As patients increasingly survive to adulthood, the need for a smooth transition into adult care is essential. Using case studies, we outline strategies and highlight the challenges of transition, illustrating practical solutions that may be used to optimise the transition process for patients with MPS disorders.

Seven MPS case studies were provided by four European inherited metabolic disease centres; six of these patients transferred to an adult care setting and the final patient remained under paediatric care. Of the patients who transferred, age at the start of transition ranged between 14 and 18 years (age at transfer ranged from 16 to 19 years).

While there were some shared features of transition strategies, they varied in duration, the healthcare professionals involved and the management of adult patients with MPS. Challenges included complex symptoms, patients' unwillingness to attend appointments with unfamiliar team members and attachment to paediatricians. Challenges were resolved by starting transition at an early age, educating patients and families, and providing regular communication with and reassurance to the patient and family. Sufficient time should be provided to allow patients to understand their responsibilities in the adult care setting while feeling assured of continued support from healthcare professionals. The involvement of a coordinated multidisciplinary team with expertise in MPS is also key. Overall, transition strategies must be comprehensive and individualised to patients' needs.

Proteomic Analysis in Morquio A Cells Treated with Immobilized Enzymatic Replacement Therapy on Nanostructured Lipid Systems

Morquio A syndrome, or mucopolysaccharidosis type IVA (MPS IVA), is a lysosomal storage disease due to mutations in the N-acetylgalactosamine-6-sulfatase (GALNS) gene. Systemic skeletal dysplasia and the related clinical features of MPS IVA are due to disruption of cartilage and its extracellular matrix, leading to an imbalance of growth. Enzyme replacement therapy (ERT) with recombinant human GALNS, alpha elosulfase, provides a systemic treatment. However, this therapy has a limited impact on skeletal dysplasia because the infused enzyme cannot penetrate cartilage and bone. Therefore, an alternative therapeutic approach to reach the cartilage is an unmet challenge. We have developed a new drug delivery system based on a nanostructure lipid carrier with the capacity to immobilize enzymes used for ERT and to target the lysosomes. This study aimed to assess the effect of the encapsulated enzyme in this new delivery system, using in vitro proteomic technology. We found a greater internalization of the enzyme carried by nanoparticles inside the cells and an improvement of cellular protein routes previously impaired by the disease, compared with conventional ERT. This is the first qualitative and quantitative proteomic assay that demonstrates the advantages of a new delivery system to improve the MPS IVA ERT.

Ophthalmological Findings in Mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a heterogenous group of lysosomal storage disorders caused by the accumulation of glycosaminoglycans (GAGs). The accrual of these compounds results in phenotypically varied syndromes that produce multi-organ impairment with widespread systemic effects. The low incidence of MPS (approximately 1/25,000 live births) in conjunction with the high childhood mortality rate had limited the availability of research into certain clinical features, especially ocular manifestations. As the recent successes of hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) have greatly increased life expectancy in these patients, they have served as a focal point for the transition of research towards improvement of quality of life. Ophthalmological findings in MPS include corneal clouding, glaucoma, optic neuropathies, and retinopathies. While corneal clouding is the most common ocular feature of MPS (especially type I, IVA, and VI), its response to HSCT and ERT is minimal. This review discusses known eye issues in the MPS subtypes, diagnosis of these ocular diseases, current clinical and surgical management, noteworthy research progress, and ultimately presents a direction for future studies.

Normalization of glycosaminoglycan-derived disaccharides detected by tandem mass spectrometry assay for the diagnosis of mucopolysaccharidosis

Mucopolysaccharidosis (MPS) is caused by the deficiency of a specific hydrolytic enzyme that catalyzes the step-wise degradation of glycosaminoglycans (GAGs). In this study, we propose an empirical method to calculate levels of GAG-derived disaccharides based on the quantity (peak areas) of chondroitin sulfate (CS) with the aim of making a diagnosis of MPS more accurate and reducing the occurrence of false positive and false negative results. In this study, levels of urinary GAG-derived disaccharides were measured in 67 patients with different types of MPS and 165 controls without MPS using a tandem mass spectrometry assay. Two different methods of reporting GAG-derived disaccharides were assessed; normalization to urinary CS (in μg/mL), and normalization to μg/mg creatinine. CS-normalization yielded more consistent values than creatinine-normalization. In particular, levels of urinary dermatan sulfate (DS), heparan sulfate (HS), and keratan sulfate (KS) significantly varied because of changes in urine creatinine levels, which were proportional to age but inversely proportional to DS, HS, and KS measurements. Using CS-normalization revealed the actual status of DS, HS, and KS without the influence of factors such as age, urine creatinine, and other physiological conditions. It could discriminate between the patients with MPS and controls without MPS, and also to evaluate changes in GAG levels pre- and post-enzyme replacement therapy.

Clinical, biochemical and genetic profiles of patients with mucopolysaccharidosis type IVA (Morquio A syndrome) in Malaysia: the first national natural history cohort study

BACKGROUND

Mucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive lysosomal storage disease due to N-acetylgalactosamine-6-sulfatase (GALNS) deficiency. It results in accumulation of the glycosaminoglycans, keratan sulfate and chondroitin-6-sulfate, leading to skeletal and other systemic impairments. Data on MPS IVA in Asian populations are scarce.

METHODS

This is a multicentre descriptive case series of 21 patients comprising all MPS IVA patients in Malaysia. Mutational analysis was performed by PCR and Sanger sequencing of the GALNS gene in 17 patients.

RESULTS

The patients (15 females and 6 males) had a mean age (± SD) of 15.5 (± 8.1) years. Mean age at symptom onset was 2.6 (± 2.1) years and at confirmed diagnosis was 6.9 (± 4.5) years. The study cohort included patients from all the main ethnic groups in Malaysia - 57% Malay, 29% Chinese and 14% Indian. Common presenting symptoms included pectus carinatum (57%) and genu valgum (43%). Eight patients (38%) had undergone surgery, most commonly knee surgeries (29%) and cervical spine decompression (24%). Patients had limited endurance with lower mean walking distances with increasing age. GALNS gene analysis identified 18 distinct mutations comprising 13 missense, three nonsense, one small deletion and one splice site mutation. Of these, eight were novel mutations (Tyr133Ser, Glu158Valfs*12, Gly168*, Gly168Val, Trp184*, Leu271Pro, Glu320Lys, Leu508Pro). Mutations in exons 1, 5 and 9 accounted for 51% of the mutant alleles identified.

CONCLUSIONS

All the MPS IVA patients in this study had clinical impairments. A better understanding of the natural history and the clinical and genetic spectrum of MPS IVA in this population may assist early diagnosis, improve management and permit timely genetic counselling and prenatal diagnosis.

Recommendations for the management of MPS IVA: systematic evidence- and consensus-based guidance

INTRODUCTION

Mucopolysaccharidosis (MPS) IVA or Morquio A syndrome is an autosomal recessive lysosomal storage disorder (LSD) caused by deficiency of the N-acetylgalactosamine-6-sulfatase (GALNS) enzyme, which impairs lysosomal degradation of keratan sulphate and chondroitin-6-sulphate. The multiple clinical manifestations of MPS IVA present numerous challenges for management and necessitate the need for individualised treatment. Although treatment guidelines are available, the methodology used to develop this guidance has come under increased scrutiny. This programme was conducted to provide evidence-based, expert-agreed recommendations to optimise management of MPS IVA.

METHODS

Twenty six international healthcare professionals across multiple disciplines, with expertise in managing MPS IVA, and three patient advocates formed the Steering Committee (SC) and contributed to the development of this guidance. Representatives from six Patient Advocacy Groups (PAGs) were interviewed to gain insights on patient perspectives. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with experience managing patients with MPS IVA and the manuscript was evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers.

RESULTS

A total of 87 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) disease-modifying interventions (enzyme replacement therapy [ERT] and haematopoietic stem cell transplantation [HSCT]); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions (including spinal, limb, ophthalmic, cardio-thoracic and ear-nose-throat [ENT] surgeries). Consensus was reached on all statements after two rounds of voting. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance).

CONCLUSION

This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS IVA and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Novel data on growth phenotype and causative genotypes in 29 patients with Morquio (Morquio-Brailsford) syndrome from Central-Eastern Europe

Mucopolysaccharidosis type IVA, also known as Morquio (Morquio-Brailsford) syndrome results from accumulation of keratan sulfate (KS) and chondroitin-6-sulfate (C6S), whereas the primary cause is mutations in the gene encoding galactosamine (N-acetyl)-6-sulfatase (GALNS). Phenotypically it seems to be a well-defined condition, with two main clinical forms: mild (attenuated) and severe, which are determined based on a combination of symptoms, i.e., enzymatic activity of GALNS, age of onset, and symptom severity. Nevertheless, the natural history of MPSIVA in relation to specific anthropometric parameters (growth, head circumference, body proportions, and face phenotype) is not precisely characterized. The aim of our work was to analyze the aforementioned anthropometric parameters, including correlation to molecular data (causative GALNS mutations).

Mutation spectrum and pivotal features for differential diagnosis of Mucopolysaccharidosis IVA patients with severe and attenuated phenotype

Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disease caused by biallelic mutations in GALNS gene and characterized by progressive skeletal deformities with short stature. The aim of this study was to evaluate the genotype, longitudinal height measurement and clinical features of MPS IVA patients. Thirty-two patients from 22 families were enrolled. The ages of patients at diagnosis ranged from two months to 18 years of age, and followed up for three to twenty years. They were classified as severe and attenuated form (intermediate and mild) according to their height measurements. The mean height standard deviation scores (SDS) for Turkish standards at 0-3, 5 and 10 years of ages were found to be -1.1, -4.2 and -7.3 respectively in patients with severe phenotype, while they were +0.4, -1.5 and -3 for intermediate phenotype. Patients with severe form reached a mean final height of -8.5 SDS, and mild phenotype -3.6 SDS. The most common initial and current symptoms in the patients with the severe phenotype were pectus carinatus and/or kyphosis deformities which occurred between 5 months and 3 years of age, and genu valgum deformity which developed after 3 years of age. However, kyphoscoliosis was the most common initial and current findings in the attenuated phenotype. Although, initial symptoms appeared in early childhood in the intermediate phenotype, similar to the severe phenotype, the clinical findings progressed slowly and genu valgum deformity did not develop. In patients with mild phenotype, the onset of symptoms was after 5 years of age. In conclusion, this study provides significant insights into the initial and follow-up clinical features and height values that contribute to the differential diagnosis of the severe and intermediate phenotypes in early childhood. Eleven mutations in GALNS gene in which one of them is novel (c.416G>A) were associated with the severe phenotype and three mutations (c.1038C>A, c.850T>G, c.752G>A) lead to the attenuated phenotype.

Critical review of current MPS guidelines and management

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders that impair degradation of glycosaminoglycans (GAG). The specific GAGs that accumulate depend on the type of MPS, leading to unique characteristic clinical features. Development of guidelines for treatment of MPS has traditionally been multifaceted and largely based on palliative care. In the last three decades, hematopoietic stem cell transplantation and enzyme replacement therapy have been developed based on experimental and clinical studies. Guidelines have been established with the accumulation of the clinical data from natural history of the disease and therapeutic consequences, mainly sponsored by pharmaceutical companies. In recent years, committees in three countries, Australia (2015), Japan (2017), and Brazil (2018) have adopted guidelines for the treatment of MPS II, sponsored and authorized by each government. As novel treatments for MPS including substrate reduction therapy, pharmacological chaperone therapy, and gene therapy become clinically available, it is increasingly necessary to establish the optimal guideline for each type of MPS, considering multiple factors including therapeutic efficacy, adverse effects, age, disease stage, prognosis, feasibility and availability of access to treatment, and cost- performance. In this article, we discuss the historical guidelines for specific MPS types and the most recently adopted guidelines for MPS II and propose the development of future guidelines without conflict of interest and bias leading to mutual benefits to all parties including patients and families, professionals, tax payers, and governments.