Heart and Cardiovascular Involvement in Patients with Mucopolysaccharidosis Type IVA (Morquio-A Syndrome)

Natural history of valve disease in patients with mucopolysaccharidosis II and the impact of enzyme replacement therapy

Mucopolysaccharidosis II (MPS II, Hunter syndrome) is a rare, X-linked lysosomal storage disease caused by reduced activity of iduronate-2-sulfatase (I2S), with subsequent cellular accumulation of the glycosaminoglycans (GAGs), heparan sulfate, and dermatan sulfate (DS). DS is a major component of the extracellular matrix of heart valves, which can be affected in MPS II. We investigated the natural history of valve disease in MPS II and the impact of long-term intravenous enzyme replacement therapy (ERT) with recombinant I2S (idursulfase). In total, 604 cardiac examinations were assessed from serial follow-up of 80 male patients (49 neuronopathic). Valve disease was classified according to standard practice from hemodynamic features evident from echocardiography. The natural history group comprised 48 patients (up to 14.8 years of follow-up; median, 2.6 years; 24 patients started ERT during the study); 56 patients were treated (up to 14.2 years of follow-up; median, 6.2 years). Lifetime GAG burden (calculated from urinary GAG measurements) correlated significantly with the degree of valve disease. Onset of moderate-to-severe valve disease was significantly delayed in treated (median age at onset, 29.1 ± 2 [95% CI: 25.2-32.9] years; Kaplan-Meier estimation) versus untreated patients (17.6 ± 1 [95% Cl: 15.8-19.4] years; p < 0.0001). Cox regression modeling found that long-term ERT reduced the probability of developing severe valve disease (χ2, 32.736; significant after 5 years of ERT). Overall, this study found that valve disease severity in MPS II correlates with GAG burden and that progression is delayed by long-term ERT.

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

Natural history of cardiac findings in mucopolysaccharidosis type I: report from an international registry

Mucopolysaccharidosis type I is an inborn error of glycosaminoglycan catabolism with phenotypes ranging from severe (Hurler syndrome) to attenuated (Hurler-Scheie and Scheie syndromes). Cardiovascular involvement is common and contributes significantly to morbidity and mortality. We conducted a retrospective analysis of the prevalence and natural history of cardiac abnormalities in treatment-naïve individuals enrolled in the international Mucopolysaccharidosis Type I Registry. Interrogation of echocardiography data (presence of cardiac valve regurgitation and/or stenosis; measurements of left ventricular chamber dimensions in diastole and systole, diastolic left ventricular posterior wall and interventricular septal thicknesses and ventricular systolic function (shortening fraction)) showed that mitral regurgitation was the most common and earliest finding for individuals with both severe (58.3%, median age 1.2 years) and attenuated (74.2%, median age 8.0 years) disease. Left-sided valve stenosis was also common in individuals with attenuated disease (mitral 30.3%; aortic 25%). Abnormal ventricular wall and septal thickness (Z-scores ≥2) were observed early in both phenotypes. Z-scores for diastolic left ventricular posterior wall and interventricular septal thicknesses increased with age in the severe phenotype (annualised slopes of 0.2777 [p = 0.037] and 0.3831 [p = 0.001], respectively); a similar correlation was not observed in the attenuated phenotype (annualised slopes of -0.0401 [p = 0.069] and -0.0029 [p = 0.875], respectively). Decreased cardiac ventricular systolic function (defined as shortening fraction <28%) was uncommon but, when noted, was more frequent in infants with the severe phenotype. While cardiac abnormalities occur early in both severe and attenuated mucopolysaccharidosis type I, the pattern of valve dysfunction and progression of ventricular abnormalities vary by phenotype.

Evaluation of cardiac findings in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidoses (MPS) are a group of rare genetic diseases and heart involvement is one of the important conflicts in most types, which may cause serious complications. We used M-Mode and two-dimensional speckle tracking echocardiography (2D-STE) to explore cardiovascular involvements in MPS patients.

METHOD

The present cross-sectional study investigated the frequency of cardiac involvements in MPS patients. Included participants were MPS types I, II, III, IV, and VI who underwent specialized echocardiography exams to assess valvular function, systolic and diastolic function, left ventricular ejection fraction (LVEF), and global longitudinal strain (GLS).

RESULTS

35 patients were enrolled in this study. The total mean age of patients was 9.58 ± 5.11 years and 71.4% were male. Type IV (40%) and type III (31.4%) were the most frequent MPS. Although LVEF did not differ notably among MPS types, GLS was significantly different (p = 0.029). Mitral regurgitation was observed remarkably more in MPS type III (p = 0.001) while mitral stenosis was more common in type III (p = 0.007). There was a significant association between LVEF and GLS (β= -0.662; p = 0.025) and between LVEF and MPS type (β = 1.82; p = 0.025) when adjusted for GLS.

CONCLUSION

Cardiac complications are very common and are one of the most important causes of death in MPS patients. 2D-STE seems to be superior to M-Mode for detection of early and subclinical cardiac dysfunction in MPS patients.

Modeling of the chest wall response to prolonged bracing in pectus carinatum

Pectus carinatum is a chest wall deformity that is often treated through the wearing of an external brace. The treatment of the deformity could benefit from a greater understanding of chest wall characteristics under prolonged loading. These characteristics are difficult to model directly but empirical studies can be used to create statistical models. 185 patients from 2018-2020 received bracing treatment. Data on the severity of the deformity, treatment pressures, and time of wear were recorded at the first fitting and all subsequent follow-up visits. This data was analyzed using a statistical mixed effects model to identify significant measures and trends in treatment. These models were designed to help quantify changes in chest wall characteristics through prolonged bracing. Two statistical models were created. The first model predicts the change in the amount of pressure to correct the deformity after bracing for a given time and pressure. The second model predicts the change in pressure response by the body on the brace after bracing for a given time and pressure. These models show a high significance in the amount of pressure and time to the changes in the chest wall response. Initial deformity severity is also significant in changes to the deformity. The statistical models predict general trends in pectus carinatum brace treatment and can assist in creating treatment plans, motivating patient compliance, and can inform the design of future treatment systems.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

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.

Mucopolysaccharidosis Type IVA: Extracellular Matrix Biomarkers in Cardiovascular Disease

Cardiovascular disease (CVD) in Mucopolysaccharidosis Type IVA (Morquio A), signified by valvular disease and cardiac hypertrophy, is the second leading cause of death and remains untouched by current therapies. Enzyme replacement therapy (ERT) is the gold-standard treatment for MPS disorders including Morquio A. Early administration of ERT improves outcomes of patients from childhood to adulthood while posing new challenges including prognosis of CVD and ERT's negligible effect on cardiovascular health. Thus, having accurate biomarkers for CVD could be critical. Here we show that cathepsin S (CTSS) and elastin (ELN) can be used as biomarkers of extracellular matrix remodeling in Morquio A disease. We found in a cohort of 54 treatment naïve Morquio A patients and 74 normal controls that CTSS shows promising attributes as a biomarker in young Morquio A children. On the other hand, ELN shows promising attributes as a biomarker in adolescent and adult Morquio A. Plasma/urine keratan sulfate (KS), and urinary glycosaminoglycan (GAG) levels were significantly higher in Morquio A patients (p < 0.001) which decreased with age of patients. CTSS levels did not correlate with patients' phenotypic severity but differed significantly between patients (median range 5.45-8.52 ng/mL) and normal controls (median range 9.61-15.9 ng/mL; p < 0.001). We also studied α -2-macroglobulin (A2M), C-reactive protein (CRP), and circulating vascular cell adhesion molecule-1 (sVCAM-1) in a subset of samples to understand the relation between ECM biomarkers and the severity of CVD in Morquio A patients. Our experiments revealed that CRP and sVCAM-1 levels were lower in Morquio A patients compared to normal controls. We also observed a strong inverse correlation between urine/plasma KS and CRP (p = 0.013 and p = 0.022, respectively) in Morquio A patients as well as a moderate correlation between sVCAM-1 and CTSS in Morquio A patients at all ages (p = 0.03). As the first study to date investigating CTSS and ELN levels in Morquio A patients and in the normal population, our results establish a starting point for more elaborate studies in larger populations to understand how CTSS and ELN levels correlate with Morquio A severity.

Progression of Cardiovascular Manifestations in Adults and Children With Mucopolysaccharidoses With and Without Enzyme Replacement Therapy

Background: Cardiovascular involvement is among the main features of MPS disorders and it is also a significant cause of morbidity and mortality. The range of manifestations includes cardiac valve disease, conduction abnormalities, left ventricular hypertrophy, and coronary artery disease. Here, we assessed the cardiovascular manifestations in a cohort of children and adults with MPS I, II, IV, and VI, as well as the impact of enzyme replacement therapy (ERT) on those manifestations.

Methods: We performed a chart review of 53 children and 23 adults with different types of MPS that had performed echocardiograms from January 2000 until October 2018. Standardized Z scores were obtained for heart chamber sizes according to the body surface area. When available, echocardiographic measurements that were performed before ERT and at least 18 months after that date were used for the assessment of pre- and post-treatment parameters.

Results: Left side valvular disease was a frequent finding, with mitral and aortic thickening being reported in most patients in all four MPS types. Left atrium dilatation was present in 26% of the patients; 25% had increased relative wall thickness; 28% had pulmonary hypertension. The cardiovascular involvement was, in general, more prevalent and more severe in adults than in children, including conduction disorders (40 vs. 16%), mitral stenosis (26 vs. 6%), aortic stenosis (13 vs. 4%), and systolic dysfunction (observed in only one adult patient). ERT promoted a significant reduction of the left ventricular hypertrophy parameters, but failed to improve valve abnormalities, pulmonary hypertension, and left atrial dilatation.

Conclusions: Adult patients with MPS may develop severe cardiovascular involvement, not commonly observed in children, and clinicians should be aware of the need for careful monitoring and timely management of those potentially life-threatening complications. Our results also confirm the impact of long-term ERT on left ventricular hypertrophy and its limitations in reversing other prevalent cardiovascular manifestations.

Activity of daily living in mucopolysaccharidosis IVA patients: Evaluation of therapeutic efficacy

Background

Mucopolysaccharidosis IVA (MPS IVA, also called Morquio A syndrome) is caused by a deficiency of N‐acetylglucosamine‐6‐sulfate sulfatase (GALNS) and results in skeletal dysplasia symptoms such as short stature and abnormal gait. Treatments include enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), but the effects are limited depending on the age of initiation and clinical phenotype. Thus, this study aims to assess the effects of treatments on MPS IVA patients compared to untreated MPS IVA patients and an age‐matched control group.

Methods

We used activity of daily living (ADL) survey with 4 sections: “movement,” “movement with cognition,” “cognition,” and “other MPS symptoms.” Lower scores indicate more assistance required. This study included 161 patients, 270 total surveys, and 70 patients with longitudinal data.

Results

We describe 134 severe patients and 25 attenuated patients. ERT and HSCT treatment improved only the “other MPS symptoms” section in severe patients. There were no differences between ERT and HSCT severe patient scores. A 19‐year‐old male patient, who had robust physical training, provided a significant increase in “movement” without treatment, suggesting the importance of exercise.

Conclusion

Overall, this ADL questionnaire has demonstrated validation and reliability in assessing the MPS IVA patients and therapeutic efficacy.

Treatment of skeletal and non-skeletal alterations of Mucopolysaccharidosis type IVA by AAV-mediated gene therapy

Mucopolysaccharidosis type IVA (MPSIVA) or Morquio A disease, a lysosomal storage disorder, is caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency, resulting in keratan sulfate (KS) and chondroitin-6-sulfate accumulation. Patients develop severe skeletal dysplasia, early cartilage deterioration and life-threatening heart and tracheal complications. There is no cure and enzyme replacement therapy cannot correct skeletal abnormalities. Here, using CRISPR/Cas9 technology, we generate the first MPSIVA rat model recapitulating all skeletal and non-skeletal alterations experienced by patients. Treatment of MPSIVA rats with adeno-associated viral vector serotype 9 encoding Galns (AAV9-Galns) results in widespread transduction of bones, cartilage and peripheral tissues. This led to long-term (1 year) increase of GALNS activity and whole-body correction of KS levels, thus preventing body size reduction and severe alterations of bones, teeth, joints, trachea and heart. This study demonstrates the potential of AAV9-Galns gene therapy to correct the disabling MPSIVA pathology, providing strong rationale for future clinical translation to MPSIVA patients.

The youngest pair of siblings with Mucopolysaccharidosis type IVA to receive enzyme replacement therapy to date: A case report

Mucopolysaccharidosis type IVA (OMIM 253000) is an autosomal recessive disorder caused by defective activity of the N-acetylgalactosamine 6-sulfatase (GALNS) enzyme. In 2014, enzyme replacement therapy (ERT) using recombinant human GALNS became available for affected patients. There is a limited number of studies to date that have explored the effect of ERT in infancy and there is also a lack of data assessing the effect of ERT in systems other than the skeletal. Here, we report on the effect of ERT in the youngest pair of siblings treated to date: Patient A, currently 4 years old, who started treatment at the age of 5 months; and Patient B, currently 3 years old, who started treatment at 58 days of life. Moreover, we investigate the effect of early ERT on the cardiovascular system. Our results show that, even when ERT is started before 2 months of age, it cannot fully prevent disease progression. As for the effect of ERT on the cardiovascular system, our preliminary results suggest that early treatment might play a role in preserving a normal left ventricular mass index in affected patients at least up to 1 year, but further observation over time will be required. Overall, this report shows that early diagnosis remains crucial and that prompt initiation of ERT has limited effect in slowing progression of the skeletal phenotype, thus confirming the need for new therapeutic approaches that target the skeletal system in affected patients.

Enzyme replacement therapy interruption in mucopolysaccharidosis type IVA patients and its impact in different clinical outcomes

Mucopolysaccharidosis type IVA (MPS IVA) is an autosomal recessive lysosomal storage disorder caused by mutations in the GALNS gene, which leads to deficient activity of N-acetylglucosamine-6-sulfate sulfatase. MPS IVA patients usually present skeletal dysplasia, coarse features, short stature, airway obstruction, cervical spinal cord compression, dental abnormalities, and cardiac valvular alterations. Enzyme replacement therapy (ERT) with elosulfase alfa is the only disease-specific treatment available for MPS IVA patients and has been shown to improve important clinical and biochemical parameters; however, little is known about the effects of ERT interruption on these patients. In this article, we report the impact of different periods of treatment interruption on clinical outcomes of 18 MPS IVA patients. All MPS IVA patients included in this case series were treated and followed up in Latin American centers and had been receiving elosulfase alfa intravenously for at least 8 months before ERT was interrupted. Different clinical parameters and assessments were evaluated at variable timepoints following therapy interruption. Altogether, our report indicates that some beneficial ERT effects in MPS IVA patients may last after different periods of treatment interruption, as cardiac and respiratory function improvements. However, worsening of important disease parameters after ERT interruption, such as the increase in uGAGs, pain, joint and skeletal aspects, and surgery indications suggests that treatment discontinuation should be avoided in order to maintain the disease as stable as possible, aiming to optimize these patients' life expectancy and quality of life.

Clinical and biochemical footprints of inherited metabolic diseases. IV. Metabolic cardiovascular disease

Inherited metabolic diseases account for 15-20% of all cases of pediatric cardiomyopathy, with a high mortality of 15-47%. Metabolic diseases can also commonly be associated with other types of cardiovascular involvement such as arrhythmias, valvulopathy or vasculopathy. We reviewed and updated the list of known metabolic etiologies associated with cardiovascular involvement, and found 246 relevant inborn errors of metabolism. This represents the fourth of a series of articles attempting to create and maintain a comprehensive list of clinical and metabolic differential diagnoses according to system involvement.

Aortic Root Dilatation in Taiwanese Patients with Mucopolysaccharidoses and the Long-Term Effects of Enzyme Replacement Therapy

Background: Cardiovascular abnormalities have been observed in patients with mucopolysaccharidosis (MPS) of any type, with the most documented abnormalities being valvular regurgitation and stenosis and cardiac hypertrophy. Only a few studies have focused on aortic root dilatation and the long-term effects of enzyme replacement therapy (ERT) in these patients. Methods: We reviewed echocardiograms of 125 Taiwanese MPS patients (age range, 0.1 to 19.1 years; 11 with MPS I, 49 with MPS II, 25 with MPS III, 29 with MPS IVA, and 11 with MPS VI). The aortic root diameter was measured at the sinus of Valsalva. Results: Aortic root dilatation (z score >2) was observed in 47% of the MPS patients, including 66% of MPS IV, 51% of MPS II, 45% of MPS VI, 28% of MPS III, and 27% of MPS I patients. The mean aortic root diameter z score was 2.14 (n = 125). The patients with MPS IV had the most severe aortic root dilatation with a mean aortic root diameter z score of 3.03, followed by MPS II (2.12), MPS VI (2.06), MPS III (1.68), and MPS I (1.03). The aortic root diameter z score was positively correlated with increasing age (n = 125, p < 0.01). For the patients with MPS II, III, and IV, aortic root diameter z score was also positively correlated with increasing age (p < 0.01). For 16 patients who had received ERT and had follow-up echocardiographic data (range 2.0–16.2 years), the mean aortic root diameter z score change was −0.46 compared to baseline (baseline 2.49 versus follow-up 2.03, p = 0.490). Conclusions: Aortic root dilatation was common in the patients with all types of MPS, with the most severe aortic root dilatation observed in those with MPS IV. The severity of aortic root dilatation worsened with increasing age, reinforcing the concept of the progressive nature of this disease. ERT for MPS appears to stabilize the progression of aortic root dilatation.

Cardiac rhythm abnormalities - An underestimated cardiovascular risk in adult patients with Mucopolysaccharidoses

Patients with Mucopolysaccharidosis (MPS) have an increased risk of cardiovascular complications, conduction tissue abnormalities and arrhythmia; all rare but underestimated. It has been reported that conduction system defects are progressive in this group of patients and may result in sudden cardiac death. The aim of this study is to review our current practice and suggest best practice guidelines regarding the frequency of cardiac rhythm monitoring in this patient group. Seventy-seven adult MPS patients who attended metabolic clinics between 2013 and 2019 were included in this retrospective observational study. Patients were affected with different MPS types: MPS I (n = 33), MPS II (n = 16), MPS IV (n = 19), VI (n = 8) and VII (n = 1). The assessments included: 12‑lead electrocardiogram (ECG), 24-h ECG (Holter monitor), loop recorder/pacemaker interrogation assessment. Data from 12‑lead ECG (available from 69 patients) showed a variety of abnormalities: T wave inversion in a single lead III (n = 19), left ventricular hypertrophy (n = 14), early repolarization (n = 14), right axis deviation (RAD, n = 11), partial RBBB (n = 9), right bundle branch block (RBBB) (n = 1) and first degree AV block (n = 1). ECG changes of bundle branch block, RAD (left posterior fascicular block) could represent conduction tissue abnormality and equally could be related to the underlying lung tissue abnormality which is present in most of the patients with MPS. T wave abnormality in a single lead is usually insignificant in healthy individuals; however in MPS patients it could be as a result of chest shape. Among the 34 patients for who 24-hour ECG was available, sinus tachycardia was the most common rhythm noted (n = 9), followed by sinus bradycardia (n = 4), atrial fibrillation (AF) (n = 1) and atrio-ventricular nodal re-entry tachycardia (AVNRT) (n = 1). Permanent pacemaker was inserted in two patients. AF was observed in one patient with MPS II. In conclusion, we postulate that regular cardiac monitoring is required to warrant early detection of underlying conduction tissue abnormalities. In addition, 12‑lead ECG is the first line investigation that, if abnormal, should be followed up by 24-hour Holter monitoring. These findings warrant further research studies.

Liver-Targeted AAV8 Gene Therapy Ameliorates Skeletal and Cardiovascular Pathology in a Mucopolysaccharidosis IVA Murine Model

Mucopolysaccharidosis type IVA (MPS IVA) is due to the deficiency of GALNS (N-acetylgalactosamine 6-sulfate sulfatase) and is characterized by systemic skeletal dysplasia. We have evaluated adeno-associated virus 8 (AAV8) vectors expressing different forms of human GALNS under a liver-specific promoter. The vectors were delivered intravenously into 4-week-old MPS IVA knockout (KO) and immune tolerant (MTOL) mice at a dose of 5 × 10¹³ genome copies (GC)/kg. These mice were monitored for 12 weeks post-injection. GALNS enzyme activity was elevated significantly in plasma of all treated mice at 2 weeks post-injection. The activity observed was 4- to 19-fold higher than that in wild-type mice and was maintained throughout the monitoring period. Treatment with AAV vectors resulted in a reduction of keratan sulfate (KS) levels in plasma to normal levels 2 weeks post-injection, which were maintained until necropsy. Both vectors reduced the storage in articular cartilage, ligaments, and meniscus surrounding articular cartilage and growth plate region as well as heart muscle and valves. Our results suggest that the continuous presence of high levels of circulating enzyme increases the penetration into bone and heart and reduces the KS level, thereby improving storage in these regions. The current data support a strategy for developing a novel treatment to address the bone and heart disease in MPS IVA using AAV gene therapy.

Transcriptomic Changes Related to Cellular Processes with Particular Emphasis on Cell Activation in Lysosomal Storage Diseases from the Group of Mucopolysaccharidoses

Although mucopolysaccharidoses (MPS), inherited metabolic diseases from the group of lysosomal storage diseases (LSD), are monogenic disorders, recent studies indicated that their molecular mechanisms are complicated. Storage of glycosaminoglycans (GAGs), arising from a deficiency in one of the enzymes involved in the degradation of these compounds, is the primary cause of each MPS type. However, dysfunctions of various cellular organelles and disturbance of cellular processes have been reported which contribute considerably to pathomechanisms of the disease. Here, we present a complex transcriptomic analysis in which all types and subtypes of MPS were investigated, with special emphasis on genes related to cell activation processes. Complex changes in expression of these genes were found in fibroblasts of all MPS types, with number of transcripts revealing higher or lower levels (relative to control fibroblasts) between 19 and over 50, depending on MPS type. Genes in which expression was significantly affected in most MPS types code for proteins involved in following processes, classified according to Gene Ontology knowledge database: cell activation, cell growth, cell recognition, and cell division. Levels of some transcripts (including CD9, CLU, MME and others) were especially significantly changed (over five times relative to controls). Our results are discussed in the light of molecular pathomechanisms of MPS, indicating that secondary and/or tertiary changes, relative to GAG storage, might significantly modulate cellular dysfunctions and contribute to molecular mechanisms of the disease. This may influence the efficacy of various therapies and suggests why various treatments are not fully effective in improving the complex symptoms of MPS.

Intravenous Enzyme Replacement Therapy in Mucopolysaccharidoses: Clinical Effectiveness and Limitations

The aim of this review is to summarize the evidence on efficacy, effectiveness and safety of intravenous enzyme replacement therapy (ERT) available for mucopolysaccharidoses (MPSs) I, II, IVA, VI and VII, gained in phase III clinical trials and in observational post-approval studies. Post-marketing data are sometimes conflicting or controversial, possibly depending on disease severity, differently involved organs, age at starting treatment, and development of anti-drug antibodies (ADAs). There is general agreement that ERT is effective in reducing urinary glycosaminoglycans and liver and spleen volume, while heart and joints outcomes are variable in different studies. Effectiveness on cardiac valves, trachea and bronchi, hearing and eyes is definitely poor, probably due to limited penetration in the specific tissues. ERT does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by intravenously injected ERT. All patients develop ADAs but their role in ERT tolerance and effectiveness has not been well defined yet. Lack of reliable biomarkers contributes to the uncertainties about effectiveness. The data obtained from affected siblings strongly indicates the need of neonatal screening for treatable MPSs. Currently, other treatments are under evaluation and will surely help improve the prognosis of MPS patients.

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.

Enzyme replacement therapy for mucopolysaccharidoses; past, present, and future

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders, which lack an enzyme corresponding to the specific type of MPS. Enzyme replacement therapy (ERT) has been the standard therapeutic option for some types of MPS because of the ability to start immediate treatment with feasibility and safety and to improve prognosis. There are several disadvantages for current ERT, such as limited impact to the brain and avascular cartilage, weekly or biweekly infusions lasting 4-5 h, the immune response against the infused enzyme, a short half-life, and the high cost. Clinical studies of ERT have shown limited efficacy in preventing or resolving progression in neurological, cardiovascular, and skeletal diseases. One focus is to penetrate the avascular cartilage area to at least stabilize, if not reverse, musculoskeletal diseases. Although early intervention in some types of MPS has shown improvements in the severity of skeletal dysplasia and stunted growth, this limits the desired effect of ameliorating musculoskeletal disease progression to young MPS patients. Novel ERT strategies are under development to reach the brain: (1) utilizing a fusion protein with monoclonal antibody to target a receptor on the BBB, (2) using a protein complex from plant lectin, glycan, or insulin-like growth factor 2, and (3) direct infusion across the BBB. As for MPS IVA and VI, bone-targeting ERT will be an alternative to improve therapeutic efficacy in bone and cartilage. This review summarizes the effect and limitations on current ERT for MPS and describes the new technology to overcome the obstacles of conventional ERT.

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.

Anesthesiological risks in mucopolysaccharidoses

Background

Patients suffering from mucopolysaccharidosis are among the most complex from the anesthesiological point of view, especially regarding the management of the airway. The evidence base for anesthesia management is often limited to case reports and small case series.

Aims

To identify useful information about experience with each subtype of mucopolysaccharidosis reported in the literature and propose a guide on the best options for airway management to the anesthesiologists who take care of these patients.

Methods

A query of the PubMed database specific for “anesthesia” and “mucopolysaccharidosis” and a further query specific for “mucopolysaccharidosis and difficult airway management” was conducted. We looked for those items that offered practical guidance to anesthesiological management. We did not exclude case reports, especially those that reported a specific technique, because of their practical suggestions.

Results

We identified 15 reviews, 17 retrospective case series, 5 prospective studies, and 28 case reports that focused on airway managements in anesthesia or had practical suggestions for preoperative evaluation and risk assessment. An accurate preoperative evaluation and the need for an experienced team are emphasized in all the reviewed articles and for each type of mucopolysaccharidosis. Many suggestions on how to plan the perioperative period have been highlighted. Insertion of a laryngeal mask airway generally improves ventilation and facilitates intubation with a fiberoptic bronchoscope. Furthermore, the videolaryngoscope is very useful in making intubation easier and facilitating bronchoscope passage.

Conclusions

Patients with mucopolysaccharidosis are at high risk for anesthesia-related complications and require a high level of attention. However, a multidisciplinary approach, combined with expertise in the use of new techniques and new devices for airway management, makes anesthesiological management safer. Further research with prospective studies would be useful.

Electronic supplementary material

The online version of this article (10.1186/s13052-018-0554-1) contains supplementary material, which is available to authorized users.

Early diagnosis and management of cardiac manifestations in mucopolysaccharidoses: a practical guide for paediatric and adult cardiologists

Mucopolysaccharidoses (MPS) are a group of hereditary disorders caused by lysosomal storage of glycosaminoglycans (GAGs) and characterized by a wide variability of phenotypes from severe fetal-neonatal forms to attenuated diseases diagnosed in adult individuals. The clinical picture generally worsens with age due to progressive storage involving mucosal tissue, upper airways and lungs, bones and joints, central and peripheral nervous system, heart, liver, eye, and ear. Cardiac storage of GAGs involves valves, heart muscle, and vessels (particularly the coronary arteries), and can be specific in relation to different MPS types and enzyme defects. MPS I, II, and VI are those with the most severe cardiac involvement. The cardiologist is a key figure in MPS, and their role is expanding from cardiac-specific management to early diagnosis when the mild disease phenotypes have not yet been recognized by other specialists. Familial and personal history, electrocardiography, imaging, and laboratory findings represent important steps in the clinical investigation of these patients. New treatments have led to an increased need for cardiologists to be on the lookout for MPS patients since they can significantly improve the lives of people with MPS if they suspect the diagnosis and refer them for enzyme replacement therapy or bone marrow transplantation.

Cardiac features and effects of enzyme replacement therapy in Taiwanese patients with Mucopolysaccharidosis IVA

BACKGROUND

Cardiac abnormalities have been observed in patients with mucopolysaccharidosis (MPS) of any type, with the most documented abnormalities being valvular heart disease and cardiac hypertrophy. However, few studies have focused on the cardiac features of MPS IVA.

METHODS

We reviewed the medical records, echocardiograms, and electrocardiograms of 32 Taiwanese patients with MPS IVA (16 males and 16 females; median age, 10.8 years; age range, 1.1 to 29.1 years) as well as the echocardiographic data of six patients who received enzyme replacement therapy (ERT) for 3-6 years.

RESULTS

Echocardiographic examinations (n = 32) revealed mean z scores of left ventricular mass index (LVMI), interventricular septum diameter in diastole (IVSd), left ventricular posterior wall diameter in diastole (LVPWd), and aortic diameter of 0.94, 2.70, 0.39, and 3.26, respectively. Z scores > 2 were identified in 25%, 50%, 29%, and 69% of the LVMI, IVSd, LVPWd, and aortic diameter values, respectively. Diastolic dysfunction [reversed ratio between early and late (atrial) ventricular filling velocity (E/A ratio < 1)] was identified in four patients (13%), however, the ejection fraction was normal (50-75%) in all of the patients. Sixteen patients (50%) had valvular heart disease and most were of mild degree. Fourteen (44%) had valvular stenosis, and 10 (31%) had regurgitation. The z scores of LVMI, IVSd, LVPWd, and aortic diameter, the severity scores of aortic stenosis and regurgitation, and the existence of a thickened interventricular septum were all positively correlated with increasing age (p < 0.05). For the 14 patients with valve thickening, the z scores of LVMI, IVSd and aortic diameter were all larger than those of the 18 patients without valve thickening (p < 0.05). For two patients who started ERT at a younger age (1.4 and 2.8 years, respectively), the z scores for LVMI, IVSd, and LVPWd all decreased after ERT.

CONCLUSIONS

A large proportion of the patients with MPS IVA had valvular heart disease and cardiac hypertrophy. Cardiac abnormalities worsened with increasing age in accordance with the progressive nature of this disease. ERT appeared to be effective in stabilizing or reducing cardiac hypertrophy, and better results may have been associated with starting ERT at a younger age.

Aortic root dilatation in patients with mucopolysaccharidoses and the impact of enzyme replacement therapy

Mucopolysaccharidoses (MPS) are disorders characterized by impaired glycosaminoglycan (GAG) catabolism as a consequence of a deficiency or the absence of lysosomal enzymes directly involved in their degradation. Multiple organ systems are involved in MPS, including the cardiovascular system. Recently, aortic root dilatation (ARD) has been described in these patients. Thus, we reviewed aortic root diameter measurements in 69 MPS patients from a single center from 2000 to 2016. Aortic root diameter z scores were calculated based on data published by Colan et al. according to the body surface area (BSA) determined using the Haycock formula. The overall incidence of ARD in MPS patients was 39.1%. Higher mean z scores were present in patients with MPS IVA and VI when compared to MPS I and II. Aortic root z scores were higher in older MPS IVA patients, which may suggest a progressive ARD change in this MPS type. No significant differences were found before and after enzyme replacement therapy (ERT) in 11 patients with available data (2 with MPS I; 4 with MPS II; 2 with MPS IVA, and 3 with MPS VI). This work provides further evidence that ARD is common in different types of MPS, being especially evident in MPS IVA, but with a significant occurrence also in MPS VI.

Widespread Vasculopathy in a Patient with Morquio A Syndrome

Morquio A syndrome (mucopolysaccharidosis IV type A), an autosomal recessive lysosomal storage disorder caused by a defective N-acetylgalactosamine 6-sulfatase gene, leads to lysosomal accumulation of keratan sulfate and chondroitin 6-sulfate. This accumulation affects multiple systems and causes notable cardiovascular manifestations, such as thickening of the left-sided valves, ventricular hypertrophy, and intimal stenosis of the coronary arteries. There have been few reports of vasculopathy in this population. We present the case of a 58-year-old woman with Morquio A syndrome who was found to have aortic dilation on a routine screening echocardiogram. Magnetic resonance images revealed multiple tortuous, dilated arteries in her head, neck, and abdomen. The diffuse vasculopathy seen in this patient should prompt further study to determine whether this is an underreported phenomenon of clinical significance or an unusual finding in this rare disorder.