Imaging findings of mucopolysaccharidoses: a pictorial review

Capsular and retinaculum thickening in type II mucopolysaccharidosis: a novel MRI finding

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage diseases caused by a deficiency of glycosaminoglycan (GAG) catalytic enzymes, resulting in an accumulation of unprocessed or partly degraded GAGs in different tissues, including bones and joints. Notably, skeletal and joint abnormalities may be the first complaint that prompts patients to seek medical attention, especially in the milder forms of the disease. To our knowledge, there are no prior imaging reports that have documented capsuloligamentous thickening in patients with MPS on MRI. In this study, we present four cases of patients with clinically and genetically confirmed diagnosis of type II MPS, encompassing seven MRI examination of different joints, including cervical spine, hip, wrist, knee, and shoulder. All of the patients were male, aged between 14 and 35 years, and exhibited varying degrees of joint stiffness in the clinical examination and carpal tunnel syndrome in cases of the wrist joint was affected. None of the patients had a history of surgical procedures on the affected joint, other metabolic or deposit diseases, or sports activity practice. The MRI revealed significant capsuloligamentous and retinaculum thickening, up to eight times greater than the normal capsular thickness reported in the literature.

Macrocephaly and Finger Changes: A Narrative Review

Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians. This review aims to provide a current synthetic overview of the main acquired and genetic etiologies associated with macrocephaly and finger changes. The genetic cause encompasses several categories of diseases, including bone marrow expansion disorders, skeletal dysplasias, ciliopathies, inherited metabolic diseases, RASopathies, and overgrowth syndromes. Furthermore, autoimmune and autoinflammatory diseases are also explored for their potential involvement in macrocephaly and finger changes. The intricate genetic mechanisms involved in the formation of cranial bones and extremities are multifaceted. An excess in growth may stem from disruptions in the intricate interplays among the genetic, epigenetic, and hormonal factors that regulate human growth. Understanding the underlying cellular and molecular mechanisms is important for elucidating the developmental pathways and biological processes that contribute to the observed clinical phenotypes. The review provides a practical approach to delineate causes of macrocephaly and finger changes, facilitate differential diagnosis and guide for the appropriate etiological framework. Early recognition contributes to timely intervention and improved outcomes for affected individuals.

Mucopolysaccharidosis type II zebrafish model exhibits early impaired proteasomal-mediated degradation of the axon guidance receptor Dcc

Most of the patients affected by neuronopathic forms of Mucopolysaccharidosis type II (MPS II), a rare lysosomal storage disorder caused by defects in iduronate-2-sulfatase (IDS) activity, exhibit early neurological defects associated with white matter lesions and progressive behavioural abnormalities. While neuronal degeneration has been largely described in experimental models and human patients, more subtle neuronal pathogenic defects remain still underexplored. In this work, we discovered that the axon guidance receptor Deleted in Colorectal Cancer (Dcc) is significantly dysregulated in the brain of ids mutant zebrafish since embryonic stages. In addition, thanks to the establishment of neuronal-enriched primary cell cultures, we identified defective proteasomal degradation as one of the main pathways underlying Dcc upregulation in ids mutant conditions. Furthermore, ids mutant fish-derived primary neurons displayed higher levels of polyubiquitinated proteins and P62, suggesting a wider defect in protein degradation. Finally, we show that ids mutant larvae display an atypical response to anxiety-inducing stimuli, hence mimicking one of the characteristic features of MPS II patients. Our study provides an additional relevant frame to MPS II pathogenesis, supporting the concept that multiple developmental defects concur with early childhood behavioural abnormalities.

The importance of skeletal x-ray screening for dysostosis multiplex in the early diagnosis of mucopolysaccharidosis

PURPOSE

Our aim is the early detection of mucopolysaccharidosis (MPS) by examining the radiographs taken for reasons other than a metabolic disease, such as infection, trauma, and short stature.

METHODS

The radiographs of children who applied to outpatient and emergency clinics in our hospital between 01/01/2022 and 31/12/2022 were examined by a pediatric radiologist retrospectively without knowledge of patient information. The MPS enzyme panel and urine glycosaminoglycan analysis were performed in patients having dysostosis multiplex on radiographs. In cases with MPS detected by enzyme and urine analysis, the definitive diagnosis was confirmed by genetic analysis.

RESULTS

Skeletal radiographs of 15.104 cases admitted to our hospital were examined (11,270 chest x-ray, 314 lumbosacral spine x-ray, 2970 hand x-ray, 253 pelvis x-ray, 162 skull x-ray, and 135 complete skeletal surveys). In 67 children, dysostosis multiplex was observed in the skeletal X-ray. Among them, seven newly diagnosed MPS cases were detected. Three cases were diagnosed with MPS type 4A, two with MPS type 6, one with MPS type 2 and one with MPS type 3B. Age at diagnosis was 46.2 ± 30.6 months (range; 20-111 months). There was a history of consanguinity in 6 (85.7%) cases.

CONCLUSION

Radiographs can provide clues for diagnosing MPS before the clinical findings become prominent in children admitted to the hospital for other complaints. Therefore, X-ray screening can be performed on children in endemic regions of MPS to search for dysostosis multiplex.

Posterior Fossa Horns in Hurler Syndrome: Prevalence and Regression

Posterior fossa "horns" caused by internal hypertrophy of the occipitomastoid sutures are one of the more recently defined cranial abnormalities described in mucopolysaccharidoses, especially in Hurler Syndrome. However, details of this finding, including the development and natural history, are not well-understood. Two hundred eighty-six brain MR imaging studies of 61 patients with mucopolysaccharidosis I-Hurler syndrome treated at single institution between 1996 and 2015 were studied. Posterior fossa horn height was measured as the perpendicular distance from the tip of the horn to the expected curvature of the occipital inner table. Fifty-seven of the 61 patients (93.4%) had evidence of posterior fossa horns on at least one occasion. The initial average height of the right horn was 4.5 mm, and the left horn, 4.7 mm. Most of the posterior horns regressed before transplantation in our cohort, though the exact age was variable among the patients. Nearly all patients in our cohort had posterior fossa horns, and these horns regressed with age. The regression of the horns frequently started before transplantation. This trend has not been previously described, and it may suggest unknown effects of mucopolysaccharidosis on skull development.

Skeletal Dysplasia Families: A Stepwise Approach to Diagnosis

Skeletal dysplasias are a heterogeneous collection of genetic disorders characterized by bone and cartilage abnormalities, and they encompass over 400 disorders. These disorders are rare individually, but collectively they are common (approximate incidence of one in 5000 births). Radiologists occasionally encounter skeletal dysplasias in daily practice. In the 1980s, Professor Juergen Spranger proposed a concept suitable for the diagnosis of skeletal dysplasias termed bone dysplasia families. He stated that (a) different bone dysplasias that share a similar skeletal pattern can be grouped into a "family," (b) the final diagnosis is feasible through the provisional recognition of a pattern followed by a more careful analysis, and (c) families of bone dysplasias may be the result of similar pathogenetic mechanisms. The prototypes of bone dysplasia families include dysostosis multiplex family, achondroplasia family, spondyloepiphyseal dysplasia congenita family, and Larsen syndrome-otopalatodigital syndrome family. Since Spranger's proposal, the concept of bone dysplasia families, along with advancing genetic techniques, has been validated and further expanded. Today, this molecularly proven concept enables a simple stepwise approach to be applied to the radiologic diagnosis of skeletal dysplasias. The first step is the categorization of a given case into a family based on pattern recognition, and the second step is more meticulous observation, such as identification of different severities of the same pattern or subtle but distinctive findings. Since major skeletal dysplasias are limited in number, radiologists can be familiar with the representative patterns of these disorders. The authors describe a stepwise radiologic approach to diagnosing major skeletal dysplasia families and review the clinical and genetic features of these disorders. Published under a CC BY 4.0 license. Quiz questions for this article are available through the Online Learning Center. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Mucopolysaccharidosis Type I in Mexico: Case-Based Review

INTRODUCTION

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease present in 1:100,000 newborns. Variants in the IDUA (alpha-L-iduronidase) gene decrease the enzyme activity for glycosaminoglycans metabolism. MPS I patients exhibit clinical manifestations that fall on the Hurler, Hurler-Scheie, and Scheie syndrome spectrum.

CASE PRESENTATION

We present a male Mexican patient with respiratory exacerbations requiring recurrent hospitalizations. He showed macrocephaly, coarse facies, hepatomegaly, umbilical hernia, and dorsal kyphosis. The sequencing of the IDUA gene revealed the following genotype: c.46_57del12/c.1205G>A. He received combined therapy with hematopoietic stem cell transplantation and enzyme replacement. Mexican case reports were analyzed to estimate the prevalence of the associated genetic variants.

CONCLUSION

Despite the challenges of managing this rare disease in Mexico, our patient benefited from the combined therapy. The discrete clinical manifestations and prompt evaluation by a geneticist were crucial in establishing a diagnosis, enabling an early intervention by a multidisciplinary team. The combination of ERT before and after HSCT provided health benefits to our patient.

Proteomics identifies novel biomarkers of synovial joint disease in a canine model of mucopolysaccharidosis I

Mucopolysaccharidosis I is a lysosomal storage disorder characterized by deficient alpha-L-iduronidase activity, leading to abnormal accumulation of glycosaminoglycans in cells and tissues. Synovial joint disease is prevalent and significantly reduces patient quality of life. There is a critical need for improved understanding of joint disease pathophysiology in MPS I, including specific biomarkers to predict and monitor joint disease progression, and response to treatment. The objective of this study was to leverage the naturally-occurring MPS I canine model and undertake an unbiased proteomic screen to identify systemic biomarkers predictive of local joint disease in MPS I. Synovial fluid and serum samples were collected from MPS I and healthy dogs at 12 months-of-age, and protein abundance characterized using liquid chromatography tandem mass spectrometry. Stifle joints were evaluated postmortem using magnetic resonance imaging (MRI) and histology. Proteomics identified 40 proteins for which abundance was significantly correlated between serum and synovial fluid, including markers of inflammatory joint disease and lysosomal dysfunction. Elevated expression of three biomarker candidates, matrix metalloproteinase 19, inter-alpha-trypsin inhibitor heavy-chain 3 and alpha-1-microglobulin, was confirmed in MPS I cartilage, and serum abundance of these molecules was found to correlate with MRI and histological degenerative grades. The candidate biomarkers identified have the potential to improve patient care by facilitating minimally-invasive, specific assessment of joint disease progression and response to therapeutic intervention.

Mucopolysaccharidosis Type 1 among Children-Neuroradiological Perspective Based on Single Centre Experience and Literature Review

Mucopolysaccharidosis 1 (MPS 1) is a group of rare lysosomal genetic disorders resulting from the accumulation of undegraded glycosaminoglycans (GAGs) leading to multiorgan damage. Neurological symptoms vary from mild to severe. Neuroimaging-mainly magnetic resonance (MRI)-plays a crucial role in disease diagnosis and monitoring. Early diagnosis is of the utmost importance due to the necessity of an early therapy implementation. New imaging tools like MR spectroscopy (MRS), semiquantitative MRI analysis and applying scoring systems help substantially in MPS 1 surveillance. The presented analysis of neuroimaging manifestations is based on 5 children with MPS 1 and a literature review. The vigilance of the radiologist based on knowledge of neuroradiological patterns is highlighted.

A pictorial review of the radiographic skeletal findings in Morquio syndrome (mucopolysaccharidosis type IV)

Morquio syndrome, also known as Morquio-Brailsford syndrome or mucopolysaccharidosis type IV (MPS IV), is a subgroup of mucopolysaccharidosis. It is an autosomal recessive lysosomal storage disorder. Two subtypes of Morquio syndrome have been identified. In MPS IVA, a deficiency in N-acetylgalactosamine-6-sulfate sulfatase interrupts the normal metabolic pathway of degrading glycosaminoglycans. Accumulated undigested glycosaminoglycans in the tissue and bones result in complications leading to severe skeletal deformity. In MPS IVB, a deficiency in beta-galactosidase results in a milder phenotype than in MPS IVA. Morquio syndrome presents a variety of clinical manifestations in a spectrum of mild to severe. It classically has been considered a skeletal dysplasia with significant skeletal involvement. However, the extraskeletal features can also provide valuable information to guide further work-up to assess the possibility of the disorder. Although the disease involves almost all parts of the body, it most commonly affects the axial skeleton, specifically the vertebrae. The characteristic radiologic findings in MPS IV, such as paddle-shaped ribs, odontoid hypoplasia, vertebral deformity, metaphyseal and epiphyseal bone dysplasia, and steep acetabula, are encompassed in the term "dysostosis multiplex," which is a common feature among other types of MPS and storage disorders. Myelopathy due to spinal cord compression and respiratory airway obstruction are the most critical complications related to mortality and morbidity. The variety of clinical features, as well as overlapping of radiological findings with other disorders, make diagnosis challenging, and delays in diagnosis and treatment may lead to critical complications. Timely imaging and radiologic expertise are important components for diagnosis. Gene therapies may provide robust treatment, particularly if genetic variations can be screened in utero.

Early enzyme replacement therapy prevents dental and craniofacial abnormalities in a mouse model of mucopolysaccharidosis type VI

Mucopolysaccharidosis VI (MPS VI) is a hereditary lysosomal storage disease caused by the absence of the enzyme arylsulfatase B (ARSB). Craniofacial defects are common in MPS VI patients and manifest as abnormalities of the facial bones, teeth, and temporomandibular joints. Although enzyme replacement therapy (ERT) is the treatment of choice for MPS VI, the effects on the craniofacial and dental structures are still poorly understood. In this study, we used an Arsb-deficient mouse model (Arsbm/m) that mimics MPS VI to investigate the effects of ERT on dental and craniofacial structures and compared these results with clinical and radiological observations from three MPS VI patients. Using micro-computed tomography, we found that the craniofacial phenotype of the Arsbm/m mice was characterized by bone exostoses at the insertion points of the masseter muscles and an overall increased volume of the jaw bone. An early start of ERT (at 4 weeks of age for 20 weeks) resulted in a moderate improvement of these jaw anomalies, while a late start of ERT (at 12 weeks of age for 12 weeks) showed no effect on the craniofacial skeleton. While teeth typically developed in Arsbm/m mice, we observed a pronounced loss of tooth-bearing alveolar bone. This alveolar bone loss, which has not been described before in MPS VI, was also observed in one of the MPS VI patients. Interestingly, only an early start of ERT led to a complete normalization of the alveolar bone in Arsbm/m mice. The temporomandibular joints in Arsbm/m mice were deformed and had a porous articular surface. Histological analysis revealed a loss of physiological cartilage layering, which was also reflected in an altered proteoglycan content in the cartilage of Arsbm/m mice. These abnormalities could only be partially corrected by an early start of ERT. In conclusion, our results show that an early start of ERT in Arsbm/m mice achieves the best therapeutic effects for tooth, bone, and temporomandibular joint development. As the MPS VI mouse model in this study resembles the clinical findings in MPS VI patients, our results suggest enzyme replacement therapy should be started as early as possible.

Mucopolysaccharidosis type IV: report of 5 cases of Morquio Syndrome

Mucopolysaccharidosis type IV or Morquio Syndrome, is a lysosomal deposit disease, of autosomal recessive inheritance with a similar incidence in men and women. The clinical picture is of variable expressiveness, its phenotype is characterized by skeletal dysplasia that includes neck and short trunk, short stature, keel thorax, kyphosis, scoliosis, genus valgus, flat foot, coxa valga, gait disorders, instability of the cervical spine and wedge or ovoid vertebrae. The treatment is symptomatic, with enzyme replacement. We present a series of 5 cases, the product of 2 couples, with a confirmed diagnosis of Mucopolysaccharidosis type IV, and different clinical presentation.

Proposal of an Algorithm to Early Detect Attenuated Type I Mucopolysaccharidosis (MPS Ia) among Children with Growth Abnormalities

Background and Objectives: Diagnostic delay is common in attenuated Mucopolysaccharidosis Type I (MPS Ia) due to the rarity of the disease and the variability of clinical presentation. Short stature and impaired growth velocity are frequent findings in MPS Ia, but they rarely raise suspicion as paediatric endocrinologists are generally poorly trained to detect earlier and milder clinical signs of this condition. Materials and Methods: Following a consensus-based methodology, a multidisciplinary panel including paediatric endocrinologists, paediatricians with expertise in metabolic disorders, radiologists, and rheumatologists shared their experience on a possible clinical approach to the diagnosis of MPS Ia in children with short stature or stunted growth. Results: The result was the formation of an algorithm that illustrates how to raise the suspicion of MPS Ia in a patient older than 5 years with short stature and suggestive clinical signs. Conclusion: The proposed algorithm may represent a useful tool to improve the awareness of paediatric endocrinologists and reduce the diagnostic delay for patients with MPS Ia.

Pediatric rib pathologies: clinicoimaging scenarios and approach to diagnosis

Pathologies involving the ribs are diverse in nature, including entities specific to the pediatric population as well as shared pathologies with adults. These can be either localized within or adjacent to the rib, but may also cause rib alteration as a component of a systemic process. To better understand these disorders, we discuss several common rib pathologies in the context of their clinical presentation and pertinent imaging findings. In addition, we review the imaging modalities that may be used to evaluate the ribs. Encompassing both the clinical and imaging aspects of pediatric rib pathologies, this review aims to increase pediatric and musculoskeletal radiologists' awareness of the spectrum of disease and how to leverage a pattern-based approach.

Hurdles in treating Hurler disease: potential routes to achieve a "real" cure

Mucopolysaccharidoses (MPSs) are multiorgan devastating diseases for which hematopoietic cell transplantation (HCT) and, to a lesser extent, enzyme replacement therapy have substantially altered the course of the disease. Furthermore, they have resulted in increased overall survival, especially for Hurler disease (MPS-1). However, despite the identification of clinical predictors and harmonized transplantation protocols, disease progression still poses a significant burden to patients, although at a slower pace. To design better therapies, we need to understand why and where current therapies fail. In this review, we discuss important aspects of the underlying disease and the disease progression. We note that the majority of progressive symptoms that occur in "hard-to-treat" tissues are actually tissues that are difficult to reach, such as avascular connective tissue or tissues isolated from the circulation by a specific barrier (eg, blood-brain barrier, blood-retina barrier). Although easily reached tissues are effectively cured by HCT, disease progression is observed in these "hard-to-reach" tissues. We used these insights to critically appraise ongoing experimental endeavors with regard to their potential to overcome the encountered hurdles and improve long-term clinical outcomes in MPS patients treated with HCT.

Non-neoplastic intracranial cystic lesions: not everything is an arachnoid cyst

Intracranial cystic lesions are common findings on neuroimaging examinations, arachnoid cysts being the most common type of such lesions. However, various lesions of congenital, infectious, or vascular origin can present with cysts. In this pictorial essay, we illustrate the main causes of non-neoplastic intracranial cystic lesions, discussing their possible differential diagnoses as well as their most relevant imaging aspects.

MRI-visible perivascular spaces as an imaging biomarker in Fabry disease

Introduction

Fabry disease (FD) is an X-linked lysosomal storage disorder resulting in vascular glycosphingolipid accumulation and increased stroke risk. MRI findings associated with FD include white matter hyperintensities (WMH) and cerebral microbleeds (CMBs), suggesting the presence of cerebral small vessel disease. MRI-visible perivascular spaces (PVS) are another promising marker of small vessel disease associated with impaired interstitial fluid drainage. We investigated the association of PVS severity and anatomical distribution with FD.

Patients and methods

We compared patients with genetically proven FD to healthy controls. PVS, WMH, lacunes and CMBs were rated on standardised sequences using validated criteria and scales, blinded to diagnosis. A trained observer (using a validated rating scale), quantified the total severity of PVS. We used logistic regression to investigate the association of severe PVS with FD.

Results

We included 33 FD patients (median age 44, 44.1% male) and 20 healthy controls (median age 33.5, 50% male). Adjusting for age and sex, FD was associated with more severe basal ganglia PVS (odds ratio (OR) 5.80, 95% CI 1.03–32.7) and higher total PVS score (OR 4.03, 95% CI 1.36–11.89). Compared with controls, participants with FD had: higher WMH volume (median 495.03 mm³ vs 0, p = 0.0008), more CMBs (21.21% vs none, p = 0.04), and a higher prevalence of lacunes (21.21% vs. 5%, p = 0.23).

Conclusions

PVS scores are more severe in FD than control subjects. Our findings have potential relevance for FD diagnosis and suggest that impaired interstitial fluid drainage might be a mechanism of white matter injury in FD.

Cerebellar tumour-like aggregate of glycosaminoglycans in a MPS IIIB patient: a case report

INTRODUCTION

Mucopolysaccharidosis (MPS) IIIB is a lysosomal disorder in which a deficiency in α-N-acetylglucosaminidase impairs the degradation of heparan sulphate, which accumulates in tissues causing multiple organs dysfunction. This disease is associated with significant central nervous system (CNS) abnormalities, but a presentation with a tumour-like lesion has never been reported so far.

CLINICAL PRESENTATION

The present report describes the case of a 5-year-old girl suffering from MPS IIIB who developed a cerebellar lesion with evident mass effect. She underwent surgery with a subsequent notable improvement of her clinical picture. Surprisingly, the pathological analysis revealed the lesion to have the typical MPS features.

CONCLUSION

This case would describe a neglected possible presentation of MPS IIIB with a lesion mimicking a neoplasm, which could even be successfully treated with surgery.

Imaging features of mucopolysaccharidoses in the head and neck

Ear, Nose and Throat (ENT) involvement by mucopolysaccharidoses is very common, affecting over 90% of patients, and occurs early in the course of the disease. Airway narrowing secondary to glycosaminoglycan deposition results in greatly increased morbidity, mortality and risk of anesthetic complications in these patients. Macroglossia, restricted mouth opening, tracheobronchomalacia, adenotonsillar hypertrophy along with other factors such as a short, rigid and unstable cervical spine, cardiac disease and increased susceptibility to respiratory infections result in a high perioperative mortality and morbidity. Imaging is most beneficial for evaluation of the airway, in particular in patients with obstructive symptoms and prior to intubation. We review the ENT manifestations of mucopolysaccharidoses including airway involvement, otological, oral and dental complications. 3-D reconstructions of the trachea, which is routinely captured on CT imaging of the spine, can be of great value for planning intubation in this patient population.

Posterior fossa horns; a new calvarial finding of mucopolysaccharidoses with well-known cranial MRI features

Background/aim

Mucopolysaccharidoses (MPS) are a group of hereditary metabolic diseases. The aim of this study was to share the previously unreported calvarial finding of internal hypertrophy of the occipitomastoid sutures (IHOMS) together with some other well-known cranial MRI findings in this patient series.

Materials and methods

A retrospective evaluation was conducted of 80 cranial MRIs of patients who had been diagnosed and followed up with MPS from 2008 to 2019 in our center. Of these patients, 11 had Hurler, 14 had Hunter, 24 had Sanfilippo, 15 had Morquio, 14 had Maroteaux–Lamy, and 2 had Sly disease. The cranial MRIs were assessed in two main groups as parenchymal intradural cranial MRI findings and extradural calvarial findings.

Results

The most common parenchymal intradural cranial MRI findings were white matter signal alterations (n = 51, 63%) and perivascular space enlargements (n = 39, 48%). The most common extradural calvarial findings were J-shaped sella (n = 45, 56%) and tympanic effusion (n = 44, 55%). Although IHOMS was defined in a relatively small number of the patients (n = 12, 15%), the prevalence rate was high in MPS type I (n = 6, 54%).

Conclusion

The abnormal cranial MRI findings of the MPS patients, including the newly identified IHOMS, may provide diagnostic clues to differentiate the type of the disease in radiological imaging.

Successful management of severe coronoid process hyperplasia in a patient with mucopolysaccharidosis VI: a case report

Mucopolysaccharidoses are a group of rare lysosomal storage diseases caused by a deficiency of enzymes, which breakdown glycosaminoglycans, with consequent dysfunction of affected tissues. Mandibular coronoid hyperplasia, with associated trismus, has been recently described as a feature of the craniofacial abnormalities seen in these patients. However, the details of the surgical and post-operative management of these patients have not been previously documented. This case describes the successful management of severe trismus from coronoid process hyperplasia in a 14-year-old male, utilising an extra-oral approach for bilateral coronoidectomies and removal of exophytic zygomatic bone, followed by immediate and long-term physiotherapy. An improvement of mandibular opening from 8 to 45 mm has been maintained at 18 months post operation.

Adjunct Diagnostic Value of Transcranial Magnetic Stimulation in Mucopolysaccharidosis-Related Cervical Myelopathy: A Pilot Study

BACKGROUND

Cervical myelopathy (CM) is a common cause of morbidity and disability in patients with mucopolysaccharidosis (MPS) and, therefore, early detection is crucial for the best surgical intervention and follow-up. Transcranial magnetic stimulation (TMS) non-invasively evaluates the conduction through the cortico-spinal tract, also allowing preclinical diagnosis and monitoring.

METHODS

Motor evoked potentials (MEPs) to TMS were recorded in a group of eight patients with MPS-related CM. Responses were obtained during mild tonic muscular activation by means of a circular coil held on the "hot spot" of the first dorsal interosseous and tibialis anterior muscles, bilaterally. The motor latency by cervical or lumbar magnetic stimulation was subtracted from the MEP cortical latency to obtain the central motor conduction time. The MEP amplitude from peak to peak to cortical stimulation and the interside difference of each measure were also calculated.

RESULTS

TMS revealed abnormal findings from both upper and lower limbs compatible with axonal damage and demyelination in six of them. Notably, a subclinical cervical spinal disease was detected before the occurrence of an overt CM in two patients, whereas TMS signs compatible with a CM of variable degree persisted despite surgery in all treated subjects.

CONCLUSIONS

TMS can be viewed as an adjunct diagnostic test pending further rigorous investigations.

Adjunct Diagnostic Value of Transcranial Magnetic Stimulation in Mucopolysaccharidosis-Related Cervical Myelopathy: A Pilot Study

BACKGROUND

Cervical myelopathy (CM) is a common cause of morbidity and disability in patients with mucopolysaccharidosis (MPS) and, therefore, early detection is crucial for the best surgical intervention and follow-up. Transcranial magnetic stimulation (TMS) non-invasively evaluates the conduction through the cortico-spinal tract, also allowing preclinical diagnosis and monitoring.

METHODS

Motor evoked potentials (MEPs) to TMS were recorded in a group of eight patients with MPS-related CM. Responses were obtained during mild tonic muscular activation by means of a circular coil held on the "hot spot" of the first dorsal interosseous and tibialis anterior muscles, bilaterally. The motor latency by cervical or lumbar magnetic stimulation was subtracted from the MEP cortical latency to obtain the central motor conduction time. The MEP amplitude from peak to peak to cortical stimulation and the interside difference of each measure were also calculated.

RESULTS

TMS revealed abnormal findings from both upper and lower limbs compatible with axonal damage and demyelination in six of them. Notably, a subclinical cervical spinal disease was detected before the occurrence of an overt CM in two patients, whereas TMS signs compatible with a CM of variable degree persisted despite surgery in all treated subjects.

CONCLUSIONS

TMS can be viewed as an adjunct diagnostic test pending further rigorous investigations.

Ulnar hemimelia: a report of four cases

Ulnar hemimelia is a very rare skeletal abnormality characterized by the total or partial absence of the ulna. It is reported to occur in approximately 1 per 150,000 live births. Some shortening of the forearm, radial bowing, and tendency of the hand to drift to the ulnar side of the wrist usually accompany ulnar hemimelia. Other skeletal anomalies such as humeroradial synostosis, radial head dislocation, carpal or metacarpal coalition, and digital abnormalities may also be seen in cases of ulnar hemimelia. The patients may be asymptomatic in the presence of an isolated mild ulnar deficiency. On the other hand, cases of prominent ulnar deficiency accompanied by complex upper limb abnormalities leading to severe disability may also be observed. We herein present four patients with varying degrees of ulnar hemimelia. Our first case had an isolated ulnar hemimelia, whereas the other three had additional upper limb abnormalities of different types.

Growth impairment and limited range of joint motion in children should raise suspicion of an attenuated form of mucopolysaccharidosis: expert opinion

Growth impairment together with bone and joint involvement is common to most patients with mucopolysaccharidosis (MPS) disorders. The genetic basis for these metabolic disorders involves various enzyme deficiencies responsible for the catabolism of glycosaminoglycans (GAGs). The incomplete degradation and subsequent accumulation of GAGs result in progressive tissue damage throughout the body. Bone ossification is particularly affected, with the consequent onset of dysostosis multiplex which is the underlying cause of short stature. Joint manifestations, whether joint contractures (MPS I, II, VI, VII) or hyperlaxity (MPS IV), affect fine motor skills and quality of life. Subtle decreases in growth velocity can begin as early as 2-4 years of age. Pediatricians are in the front line to recognize or suspect MPS. However, given the rarity of the disorders and variable ages of symptom onset depending on disease severity, recognition and diagnostic delays remain a challenge, especially for the attenuated forms. Prompt diagnosis and treatment can prevent irreversible disease outcomes.Conclusion: We present a diagnostic algorithm based on growth velocity decline and bone and joint involvement designed to help pediatricians recognize early manifestations of attenuated forms of MPS. We illustrate the paper with examples of abnormal growth curves and subtle radiographic nuances. What is Known: • As mucopolysaccharidoses (MPSs) are rare genetic disorders infrequently seen in clinical practice, there can be a lag between symptom onset and diagnosis, especially of attenuated forms of the disease. • This highlights the need for increased disease awareness to recognize early clinical signs and subsequently initiate early treatment to improve outcomes (normal height potential) and possibly prevent or delay the development of irreversible disease manifestations. What is New: • Growth impairment co-presenting with limited range of joint motion and radiographic anomalies in children should raise suspicions of possible attenuated MPS (AMPS). • Experts present a diagnostic algorithm with detailed focus on the decline in growth velocity, delayed puberty and limitation in joint mobility seen in children with AMPS, to shorten time-to-diagnosis and treatment and potentially improve patient outcome.

Tarsal tunnel syndrome in the mucopolysaccharidoses: A case series and literature review

BACKGROUND

The mucopolysaccharidoses (MPS) are a group of inherited, progressive, multi-system lysosomal storage disorders. Musculoskeletal manifestations include nerve entrapment syndromes, most commonly carpal tunnel syndrome. Tarsal tunnel syndrome (TTS) has also been reported. The purpose of this study was to investigate the clinical course of MPS patients with suspected TTS and to conduct a literature review of TTS in MPS.

METHODS

A review of the Medline and EMBASE databases was conducted in accordance with published guidelines from the Joanna Briggs Institute of Evidence Based Medicine with search strategy developed by a librarian trained in systematic reviews. A medical record review was undertaken for all patients managed in the multi-disciplinary MPS clinic in a tertiary referral paediatric centre, identifying patients with a suspected or established diagnosis of TTS. Data regarding the demographics, investigations, presentation, management, and clinical course were collected.

RESULTS

The literature review failed to identify any published papers regarding TTS in MPS, with conference proceedings only identified. Within a cohort of 19 MPS patients, four patients with a suspected diagnosis of TTS were identified (MPS I: two patients, MPS VI: two patients). Three patients underwent surgical tarsal tunnel decompression, two with good result. One patient had overlapping symptoms with spinal stenosis and improvement in suspected tarsal tunnel symptoms following spinal decompression and fusion.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

The role of imaging in the skeletal involvement of mucopolysaccharidoses

This article discusses the role of imaging modalities including radiography, multi-detector computed tomography, magnetic resonance imaging, and ultrasound in diagnosing and monitoring skeletal abnormalities in mucopolysaccharidoses (MPS). The advantages and disadvantages of these different imaging tools will be discussed, along with their feasibility in this class of patients. As the musculoskeletal involvement is common to all MPS and is one of the main reasons for seeking medical attention, an increased awareness among paediatricians, rheumatologists, orthopaedists, radiologists, and other musculoskeletal specialists on the possible spectrum of abnormalities observed could facilitate a timely diagnosis, an appropriate severity evaluation, and better management.

Mucopolysaccharidoses: overview of neuroimaging manifestations

The mucopolysaccharidoses are a heterogeneous group of inherited lysosomal storage disorders, characterized by the accumulation of undegraded glycosaminoglycans in various organs, leading to tissue damage. Mucopolysaccharidoses include eight individual disorders (IS [Scheie syndrome], IH [Hurler syndrome], II, III, IV, VI, VII and IX). They have autosomal-recessive transmission with the exception of mucopolysaccharidosis II, which is X-linked. Each individual disorder has a wide spectrum of phenotypic variation, depending on the specific mutation, from very mild to very severe. The skeletal and central nervous systems are particularly affected. The typical clinical presentation includes organomegaly, dysostosis multiplex with short trunk dwarfism, mental retardation and developmental delay. In this article, we review the neuroimaging manifestations of the different types of mucopolysaccharidoses including the dysostosis multiplex of the skull and spine as well as the various central nervous system complications. These include white matter injury, enlargement of the perivascular spaces, hydrocephalus, brain atrophy, characteristic enlargement of the subarachnoid spaces as well as compressive myelopathy. The correlation between several of the neuroimaging features and disease severity remains controversial, without well-established imaging biomarkers at this time. Imaging has, however, a crucial role in monitoring disease progression, in particular craniocervical junction stenosis, cord compression and hydrocephalus, because this allows for timely intervention before permanent damage occurs.

Bone health in patients with inborn errors of metabolism

Inborn errors of metabolism encompass a wide spectrum of disorders, frequently affecting bone. The most important metabolic disorders that primarily influence calcium or phosphate balance, resulting in skeletal pathology, are hypophosphatemic rickets and hypophosphatasia. Conditions involving bone marrow or affecting skeletal growth and development are mainly the lysosomal storage disorders, in particular the mucopolysaccharidoses. In these disorders skeletal abnormalities are often the presenting symptom and early recognition and intervention improves outcome in many of these diseases. Many disorders of intermediary metabolism may impact bone health as well, resulting in higher frequencies of osteopenia and osteoporosis. In these conditions factors contributing to the reduced bone mineralization can be the disorder itself, the strict dietary treatment, reduced physical activity or sunlight exposure and/or early ovarian failure. Awareness of these primary or secondary bone problems amongst physicians treating patients with inborn errors of metabolism is of importance for optimization bone health and recognition of skeletal complications.

Quantitative neuroimaging in mucopolysaccharidoses clinical trials

The mucopolysaccharidosis (MPS) disorders are rare lysosomal storage disorders caused by mutations in lysosomal enzymes involved in glycosaminoglycan (GAG) degradation. The resulting intracellular accumulation of GAGs leads to widespread tissue and organ dysfunction. In addition to somatic signs and symptoms, patients with MPS can present with neurological manifestations such as cognitive decline, behavioral problems (e.g. hyperactivity and aggressiveness), sleep disturbances, and/or epilepsy. These are associated with significant abnormalities of the central nervous system (CNS), including white and gray matter lesions, brain atrophy, ventriculomegaly, and spinal cord compression. In order to effectively manage and develop therapies for MPS that target neurological disease, it is important to visualize and quantify these CNS abnormalities. This review describes optimal approaches for conducting magnetic resonance imaging assessments in multi-center clinical studies, and summarizes current knowledge from neuroimaging studies in MPS disorders. The content of the review is based on presentations and discussions on these topics that were held during a meeting of an international group of experts.

Gibbus deformity after non-tuberculosis osteomyelitis

Gibbus deformities are characterized by anterior collapse of one or more vertebral bodies resulting in kyphosis. These deformities usually arise from spinal infections, and are traditionally associated with tuberculosis; other pathogens are rarely reported in the literature. In this case report, the authors describe a patient with a sharp, angulated Gibbus deformity presenting with back pain and myelopathy. The patient was placed on antibiotics, underwent T11-T12 corpectomy, placement of an expandable cage, and T8-L3 fusion with improvement of symptoms. Microbiology returned positive for non-tuberculosis osteomyelitis, and the postoperative course was uneventful. This report further reviews the presentation, pathology, development, and neurosurgical treatment of Gibbus deformities. Although they have become rare as rates of tuberculosis have declined, Gibbus deformities remain an important surgical entity that should be recognized by the spine surgeon.

Imaging in cutis laxa syndrome caused by a dominant negative ALDH18A1 mutation, with hypotheses for intracranial vascular tortuosity and wide perivascular spaces

The autosomal dominant progeroid form of cutis laxa is a recently identified multiple congenital anomaly disorder characterized by thin, wrinkled skin, a progeroid appearance, intra-uterine growth retardation, postnatal growth restriction, psychomotor developmental delay, microcephaly, cataract, hypotonia and contractures. De novo heterozygous mutations in ALDH18A1 have been described in this condition. We present neuroimaging abnormalities in three patients. One patient had intracranial arterial and venous tortuosity, widened ventricular and extra-axial cerebrospinal fluid (CSF) spaces, wide perivascular spaces and increased T2 signal intensity in the cerebral white matter over time. The second patient had vascular tortuosity. The third patient had prominent ventricular and extra-axial cerebrospinal fluid (CSF) spaces on CT. We propose an embryological mechanism for the development of intracranial vascular tortuosity and discuss the anatomical basis of wide perivascular spaces in relation to this syndrome. Although we do not know the clinical implications of these cerebral vascular anomalies, we suggest inclusion of neuroimaging in the baseline evaluation of these patients.

Fibrous Arthropathy Associated With Morphea: A New Cause of Diffuse Acquired Joint Contractures

Etiologies for childhood-onset diffuse joint contractures encompass a large group of inherited disorders and acquired diseases, in particular a subtype of juvenile idiopathic arthritis called "dry polyarthritis," dermatomyositis, and systemic sclerosis. We report on 2 boys, aged 5 and 8 years, who developed acquired symmetric painless joint contractures preceding the development of superficial plaques of morphea by 7 to 13 months. There was no other clinical involvement, biological inflammation, or autoantibodies. No urinary mucopolysaccharidosis was seen. In both patients, wrist MRI showed no joint effusion, no bone erosion, and no or mild synovial thickening with slight enhancement after gadolinium infusion. One patient underwent a synovial biopsy, which showed dense fibrosis with a sparse inflammatory infiltrate, similar to the pathologic pattern observed in the skin biopsy. With methotrexate and systemic steroids, joint contractures slowly improved in the first patient and remained stable in the second. These 2 cases suggest that fibrous synovitis should be considered in children with acquired diffuse, symmetric, painless contractures and without elevation of acute-phase reactants, even in the absence of cutaneous manifestations. Articular MRI with gadolinium and careful cutaneous examination at onset and during follow-up should provide clues for diagnosing this entity.

Delayed speech, hyperactivity, and coarse facies: Does Sanfilippo syndrome come to mind?

Mucopolysaccharidosis Type IIIA (MPS IIIA) or Sanfilippo-A syndrome is caused by a deficiency in lysosomal a-heparan N-sulfatase. Its clinical manifestations include progressive dementia, hyperactivity, and aggressive behavior. Unlike other mucopolysaccharide disorders, the diagnosis of MPS IIIA is challenging in both adults and children. This diagnostic challenge has been associated with the high incidence of false negative results encountered on urinary screening tests. We herein describe Sanfilippo-A syndrome in a pediatric patient who presented with progressive hyperactivity, delayed language, and developmental delay and a negative urine screening test. We emphasized that these findings may serve as possible initial presentations of MPS IIIA; therefore, screening for MPS should be done in all patients with unexplained psychomotor retardation and progressive hyperactivity.

Pediatric Chest Radiographs: Common and Less Common Errors

OBJECTIVE

Radiographic imaging of the pediatric chest presents several unique challenges and nuances, stemming from congenital variants and pathologic processes specific to this population. Errors in interpretation may lead to inappropriate further imaging, incurring additional radiation exposure and cost, as well as psychologic effects on the patients and their families.

CONCLUSION

Here, we aim to highlight some common and less common pitfalls in pediatric chest radiography, as well as some tools for avoiding potential mistakes.

Pathogenesis and treatment of spine disease in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.

Long-term cognitive follow-up in children treated for Maroteaux-Lamy syndrome

BACKGROUND

It remains unclear to what extent the brain is affected by Maroteaux-Lamy syndrome (MPS VI), a progressive lysosomal storage disorder. While enzyme replacement therapy (ERT) elicits positive effects, the drug cannot cross the blood-brain barrier. We therefore studied cognitive development and brain abnormalities in the Dutch MPS VI patient population treated with ERT.

METHODS

In a series of 11 children with MPS VI (age 2 to 20 years), we assessed cognitive functioning and brain magnetic resonance imaging prospectively at the start of ERT and at regular times thereafter up to 4.8 years. We also assessed the children's clinical characteristics, their siblings' cognitive development, and their parents' educational levels.

RESULTS

The patients' intelligence scores ranged from normal to mentally delayed (range test scores 52-131). In 90%, their scores remained fairly stable during follow-up, generally lying in the same range as their siblings' test scores (median for patients = 104, median for siblings = 88) and comparing well with the parental educational levels. Native-speaking patients had higher intelligence test scores than non-native-speaking patients. Two patients, both with high baseline glycosaminoglycan levels in their urine and severe mutations in the arylsulfatase B gene, scored clearly lower than expected. Patients with pY210C performed best. Brain abnormalities were aspecific, occurring more in patients with severe symptoms.

CONCLUSION

Our study shows that cognitive development in MPS VI patients is determined not only by familial and social-background factors, but, in patients with a severe form of the disease, also by the disease itself. Therefore in patients with severe disease presentation cognition should be monitored carefully.

Paleopathological Study of Dwarfism-Related Skeletal Dysplasia in a Late Joseon Dynasty (South Korean) Population

Skeletal dysplasias related to genetic etiologies have rarely been reported for past populations. This report presents the skeletal characteristics of an individual with dwarfism-related skeletal dysplasia from South Korea. To assess abnormal deformities, morphological features, metric data, and computed tomography scans are analyzed. Differential diagnoses include achondroplasia or hypochondroplasia, chondrodysplasia, multiple epiphyseal dysplasia, thalassemia-related hemolytic anemia, and lysosomal storage disease. The diffused deformities in the upper-limb bones and several coarsened features of the craniofacial bones indicate the most likely diagnosis to have been a certain type of lysosomal storage disease. The skeletal remains of EP-III-4-No.107 from the Eunpyeong site, although incomplete and fragmented, provide important clues to the paleopathological diagnosis of skeletal dysplasias.

Lysosomal storage diseases--the horizon expands

Since the discovery of the lysosome in 1955, advances have been made in understanding the key roles and functions of this organelle. The concept of lysosomal storage diseases (LSDs)--disorders characterized by aberrant, excessive storage of cellular material in lysosomes--developed following the discovery of α-glucosidase deficiency as the cause of Pompe disease in 1963. Great strides have since been made in understanding the pathobiology of LSDs and the neuronal ceroid lipofuscinoses (NCLs). The NCLs are neurodegenerative disorders that display symptoms of cognitive and motor decline, seizures, blindness, early death, and accumulation of lipofuscin in various cell types, and also show some similarities to 'classic' LSDs. Defective lysosomal storage can occur in many cell types, but the CNS and PNS are particularly vulnerable to LSDs and NCLs, being affected in two-thirds of these disorders. Most LSDs are inherited in an autosomal recessive manner, with the exception of X-linked Hunter disease, Fabry disease and Danon disease, and a variant type of adult NCL (Kuf disease). This Review provides a summary of known LSDs, and the pathways affected in these disorders. Existing therapies and barriers to development of novel and improved treatments for LSDs and NCLs are also discussed.

Lysosomal storage diseases--the horizon expands

Since the discovery of the lysosome in 1955, advances have been made in understanding the key roles and functions of this organelle. The concept of lysosomal storage diseases (LSDs)--disorders characterized by aberrant, excessive storage of cellular material in lysosomes--developed following the discovery of α-glucosidase deficiency as the cause of Pompe disease in 1963. Great strides have since been made in understanding the pathobiology of LSDs and the neuronal ceroid lipofuscinoses (NCLs). The NCLs are neurodegenerative disorders that display symptoms of cognitive and motor decline, seizures, blindness, early death, and accumulation of lipofuscin in various cell types, and also show some similarities to 'classic' LSDs. Defective lysosomal storage can occur in many cell types, but the CNS and PNS are particularly vulnerable to LSDs and NCLs, being affected in two-thirds of these disorders. Most LSDs are inherited in an autosomal recessive manner, with the exception of X-linked Hunter disease, Fabry disease and Danon disease, and a variant type of adult NCL (Kuf disease). This Review provides a summary of known LSDs, and the pathways affected in these disorders. Existing therapies and barriers to development of novel and improved treatments for LSDs and NCLs are also discussed.