Multifocal slowing of nerve conduction in metachromatic leukodystrophy

Newborn screening in metachromatic leukodystrophy - European consensus-based recommendations on clinical management

INTRODUCTION

Metachromatic leukodystrophy (MLD) is a rare autosomal recessive lysosomal storage disorder resulting from arylsulfatase A enzyme deficiency, leading to toxic sulfatide accumulation. As a result affected individuals exhibit progressive neurodegeneration. Treatments such as hematopoietic stem cell transplantation (HSCT) and gene therapy are effective when administered pre-symptomatically. Newborn screening (NBS) for MLD has recently been shown to be technically feasible and is indicated because of available treatment options. However, there is a lack of guidance on how to monitor and manage identified cases. This study aims to establish consensus among international experts in MLD and patient advocates on clinical management for NBS-identified MLD cases.

METHODS

A real-time Delphi procedure using eDELPHI software with 22 experts in MLD was performed. Questions, based on a literature review and workshops, were answered during a seven-week period. Three levels of consensus were defined: A) 100%, B) 75-99%, and C) 50-74% or >75% but >25% neutral votes. Recommendations were categorized by agreement level, from strongly recommended to suggested. Patient advocates participated in discussions and were involved in the final consensus.

RESULTS

The study presents 57 statements guiding clinical management of NBS-identified MLD patients. Key recommendations include timely communication by MLD experts with identified families, treating early-onset MLD with gene therapy and late-onset MLD with HSCT, as well as pre-treatment monitoring schemes. Specific knowledge gaps were identified, urging prioritized research for future evidence-based guidelines.

DISCUSSION

Consensus-based recommendations for NBS in MLD will enhance harmonized management and facilitate integration in national screening programs. Structured data collection and monitoring of screening programs are crucial for evidence generation and future guideline development. Involving patient representatives in the development of recommendations seems essential for NBS programs.

Clinical, Biochemical, and Molecular Characterization of Metachromatic Leukodystrophy Among Egyptian Pediatric Patients: Expansion of the ARSA Mutational Spectrum

Metachromatic leukodystrophy (MLD) is a neurodegenerative disorder characterized by progressive demyelination due to deficiency of the enzyme arylsulfatase A (ARSA) in leukocytes, and consequently leads to impaired degradation and accumulation of cerebroside-3-sulfate (sulfatide). This study aimed to sequence the ARSA gene in a total of 43 patients with metachromatic leukodystrophy descendant from 40 Egyptian families. In addition, four carrier parents from two families with children who had died from MLD came to the clinic for genetic analysis. Prenatal diagnosis was performed for four families with molecularly diagnosed MLD sibs. Different mutations were characterized in our cohort, including missense, nonsense, splice, and deletion. Overall, 21 different mutations in the ARSA gene were detected, with 12 novel mutations, i.e. p.Arg60Pro, p.Tyr65*, p.Val112Asp, p.Arg116*, p.Gly124Asp, p.Pro193Ser, p.Gln238*, p.Gln456*, p.Thr276Lys, and p.Gly311Arg, in addition to two new acceptor splice-site mutations 685-1G > A and c.954_956 delCTT. The amniotic fluid samples revealed two carrier fetuses with heterozygous monoallelic mutations, and two affected fetuses had the homozygous biallelic mutations. In conclusion, the current study sheds light on the underlying ARSA gene defect, with an expansion of the mutation spectrum. To our knowledge, this is the first molecular study of MLD among the Egyptian population.

Peripheral neuropathy in metachromatic leukodystrophy: current status and future perspective

Metachromatic leukodystrophy (MLD) is an autosomal recessively inherited metabolic disease characterized by deficient activity of the lysosomal enzyme arylsulfatase A. Its deficiency results in accumulation of sulfatides in neural and visceral tissues, and causes demyelination of the central and peripheral nervous system. This leads to a broad range of neurological symptoms and eventually premature death. In asymptomatic patients with juvenile and adult MLD, treatment with allogeneic hematopoietic stem cell transplantation (HCT) provides a symptomatic and survival benefit. However, this treatment mainly impacts brain white matter, whereas the peripheral neuropathy shows no or only limited response. Data about the impact of peripheral neuropathy in MLD patients are currently lacking, although in our experience peripheral neuropathy causes significant morbidity due to neuropathic pain, foot deformities and neurogenic bladder disturbances. Besides, the reasons for residual and often progressive peripheral neuropathy after HCT are not fully understood. Preliminary studies suggest that peripheral neuropathy might respond better to gene therapy due to higher enzyme levels achieved than with HCT. However, histopathological and clinical findings also suggest a role of neuroinflammation in the pathology of peripheral neuropathy in MLD. In this literature review, we discuss clinical aspects, pathological findings, distribution of mutations, and treatment approaches in MLD with particular emphasis on peripheral neuropathy. We believe that future therapies need more emphasis on the management of peripheral neuropathy, and additional research is needed to optimize care strategies.

Electroneurography and Advanced Neuroimaging Profile in Pediatric-onset Metachromatic Leukodystrophy

Context

Metachromatic leukodystrophy (MLD) is a rare autosomal-recessive disorder characterized by demyelination of central and peripheral nervous system. There is scarcity of literature on the electrophysiological aspects of peripheral nerves and the advanced neuroimaging findings in MLD.

Aim

The aim was to study the nerve conduction parameters and advanced neuroimaging findings in patients with MLD.

Materials and Methods

This study is a retrospective analysis conducted, between 2005 and 2016, of 12 patients who had biochemical, histopathological, or genetic confirmation of MLD and disease onset before 18 years of age. The clinical, electroneurography, and the advanced neuroimaging findings were reviewed and analyzed.

Statistical Analysis

The data were presented as percentages or mean ± standard deviation as defined appropriate for qualitative and quantitative variables.

Results

Mean age of onset was 4.84 (±4.60) years and seven patients were males. Eight patients had juvenile MLD and four had late infantile MLD. Clinical presentation of psychomotor regression was more common in infantile MLD (75%), whereas gait difficulty (62.5%) and cognitive impairment (37.5%) were more frequent in juvenile MLD. Nerve conduction study (NCS) revealed diffuse demyelinating sensorimotor peripheral neuropathy in 9 (75%) patients. One patient had a rare presentation with conduction blocks in multiple nerves with contrast enhancement of cauda equina. Diffusion restriction involving periventricular and central white matter was seen in five patients and bilateral globus pallidi blooming was noted in three patients.

Conclusion

This study highlights the utility of NCS and advanced magnetic resonance imaging sequences in the diagnosis of MLD.

Charcot-Marie-Tooth Disease and Other Genetic Polyneuropathies

PURPOSE OF REVIEW

Genetic polyneuropathies are rare and clinically heterogeneous. This article provides an overview of the clinical features, neurologic and electrodiagnostic findings, and management strategies for Charcot-Marie-Tooth disease and other genetic polyneuropathies as well as an algorithm for genetic testing.

RECENT FINDINGS

In the past 10 years, many of the mutations causing genetic polyneuropathies have been identified. International collaborations have led to the development of consortiums that are undertaking careful genotype-phenotype correlations to facilitate the development of targeted therapies and validation of outcome measures for future clinical trials. Clinical trials are currently under way for some genetic polyneuropathies.

SUMMARY

Readers are provided a framework to recognize common presentations of various genetic polyneuropathies and a rationale for current diagnostic testing and management strategies in genetic polyneuropathies.

Late infantile metachromatic leukodystrophy: Clinical manifestations of five Taiwanese patients and Genetic features in Asia

BACKGROUND

This study was conducted to describe the clinical and genetic features of patients with late infantile metachromatic leukodystrophy.

METHODS

Clinical and genetic manifestations of five Taiwanese patients with late infantile metachromatic leukodystrophy from January 2003 to April 2014 were reviewed. The genetic features of such patients reported in Asian countries during a period of 20 years were also analyzed.

RESULTS

The median age at disease onset was 1 year and 3 months with the first clinical symptom being gait disturbance. All five patients became bed-ridden at a median age of 2 years and 5 months. Nerve conduction velocity revealed demyelinating polyneuropathy and brain MRI disclosed tigroid and leopard skin pattern of dysmyelination in all 5 patients. All patients had decreased ARSA activities in leukocytes accounting for 15.88% to 30.75% of controls. Five novel mutations, p.A316D, p.G303R, p.Q176X, p.R293X, and c.749 insGCGGGCCA, were identified in our case series. Eighteen patients, including our 5 patients, were reported in Asian countries. A total of 22 different disease-causing alleles were found, in which p.W320X was identified in Taiwan and China, and p.G101V was found in Taiwan and Korea.

CONCLUSIONS

Patients with late infantile metachromatic leukodystrophy exhibited a rapid and devastating clinical course. The pattern of dysmyelination on brain MRI together with peripheral demyelination polyneuropathy indicates that evaluation of ARSA activity in leukocytes is warranted. A wide diversity of ARSA gene mutations was noted in Asia.

Sulfatide levels correlate with severity of neuropathy in metachromatic leukodystrophy

Objective

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disorder due to deficient activity of arylsulfatase A (ASA) that causes accumulation of sulfatide and lysosulfatide. The disorder is associated with demyelination and axonal loss in the central and peripheral nervous systems. The late infantile form has an early-onset, rapidly progressive course with severe sensorimotor dysfunction. The relationship between the degree of nerve damage and (lyso)sulfatide accumulation is, however, not established.

Methods

In 13 children aged 2–5 years with severe motor impairment, markedly elevated cerebrospinal fluid (CSF) and sural nerve sulfatide and lysosulfatide levels, genotype, ASA mRNA levels, residual ASA, and protein cross-reactive immunological material (CRIM) confirmed the diagnosis. We studied the relationship between (lyso)sulfatide levels and (1) the clinical deficit in gross motor function (GMFM-88), (2) median and peroneal nerve motor and median and sural nerve sensory conduction studies (NCS), (3) median and tibial nerve somatosensory evoked potentials (SSEPs), (4) sural nerve histopathology, and (5) brain MR spectroscopy.

Results

Eleven patients had a sensory-motor demyelinating neuropathy on electrophysiological testing, whereas two patients had normal studies. Sural nerve and CSF (lyso)sulfatide levels strongly correlated with abnormalities in electrophysiological parameters and large myelinated fiber loss in the sural nerve, but there were no associations between (lyso)sulfatide levels and measures of central nervous system (CNS) involvement (GMFM-88 score, SSEP, and MR spectroscopy).

Interpretation

Nerve and CSF sulfatide and lysosulfatide accumulation provides a marker of disease severity in the PNS only; it does not reflect the extent of CNS involvement by the disease process. The magnitude of the biochemical disturbance produces a continuously graded spectrum of impairments in neurophysiological function and sural nerve histopathology.

Progressive demyelinating neuropathy correlates with clinical severity in Cockayne syndrome

OBJECTIVE

Cockayne syndrome (CS) is characterized by postnatal growth failure and progressive multi-organ dysfunctions. CSA and CSB gene mutations account for the majority of cases and three degrees of severity are delineated. A peripheral neuropathy is known to be associated with CS but the type, severity and correlation of the nerve involvement with CS subtypes remain unknown in genetically identified patients.

METHODS

Clinical and nerve conduction studies (NCS) in 25 CS patients with CSA (n=13) CSB (n=12) mutations.

RESULTS

NCS show a widespread decrease in motor and sensory conduction velocities (CV) in all severe and classical form of CS. In one patient, CV were normal at age 8months but severe slowing was detected at 2years. Conduction block and/or temporal dispersion were observed in 68% of patients.

CONCLUSIONS

CS is associated with a progressive sensory and motor neuropathy. Signs of segmental demyelination, including conduction blocks, may not be obvious before the age of 2years. CV slowing is correlated with the CS clinical severity.

SIGNIFICANCE

NCS should be performed in patients with suspected CS as an additional tool to guide the diagnosis before molecular studies. Further studies focused on NCS course are required in order to assess its relevance as a biomarker in research therapy projects.

Leukodystrophy presenting as acute-onset polyradiculoneuropathy

BACKGROUND

Sulfatides, the most abundant glycosphingolipids, are a major component of myelin. They are degraded by the combined action of sphingolipid activator protein and arylsulfatase A. Deficiency of either of these entities causes metachromatic leukodystrophy (MLD). On the basis of age of onset, this entity is divided into late infantile, juvenile, and adult subtypes. Late infantile form, the commonest subtype, can exhibit peripheral neuropathy as the initial manifestation. The other two forms usually manifest peripheral neuropathy later in the disease course.

PATIENT

A 1.5-year-old girl with preexisting isolated motor delay presented with acute-onset ascending flaccid quadriparesis, ptosis, and respiratory failure. Ptosis and respiratory failure responded completely to intravenous immunoglobulin, whereas quadriparesis showed minimal improvement. Nerve biopsy revealed metachromatic granules with demyelination, and serum arylsulfatase A levels were undetectable.

CONCLUSION

The severity and nature of the disease coupled with the response to immunotherapy makes this case unusual. This child may represent either an atypical presentation of MLD with coincidental response to immunotherapy or an episode of immune mediated neuropathy in an individual with already diseased nerves due to MLD.

Demyelinating prenatal and infantile developmental neuropathies

The prenatal and infantile neuropathies are an uncommon and complex group of conditions, most of which are genetic. Despite advances in diagnostic techniques, approximately half of children presenting in infancy remain without a specific diagnosis. This review focuses on inherited demyelinating neuropathies presenting in the first year of life. We clarify the nomenclature used in these disorders, review the clinical features of demyelinating forms of Charcot-Marie-Tooth disease with early onset, and discuss the demyelinating infantile neuropathies associated with central nervous system involvement. Useful clinical, neurophysiologic, and neuropathologic features in the diagnostic work-up of these conditions are also presented.

Leukodystrophies

Leukodystrophies comprise a broad group of progressive, inherited disorders affecting mainly myelin. They often present after a variable period of normalcy with a variety of neurologic problems. Though the ultimate diagnosis is not found in many patients with leukodystrophies, distinctive features unique to them aid in diagnosis, treatment and prognostication. The clinical characteristics, etiologies, diagnostic testing and treatment options are reviewed in detail for some of the major leukodystrophies: X-linked adrenoleukodystrophy, Krabbe disease, metachromatic leukodystrophy, Pelizaeus-Merzbacher disease, Alexander disease, Canavan disease, megalencephalic leukoencephalopathy with subcortical cysts and vanishing white matter disease.

An unusual homozygous arylsulfatase: a pseudodeficiency in a metachromatic leukodystrophy Tunisian patient

Metachromatic leukodystrophy is an autosomal recessive neurodegenerative lysosomal disease characterized by a deficiency of the lysosomal enzyme arylsulfatase A and the subsequent accumulation of sulfatide in neuronal and visceral tissues. Clinical diagnosis is usually confirmed by in vitro analysis of arylsulfatase A activity but may be complicated in cases of arylsulfatase A pseudodeficiency and sphingolipid activators protein deficiency. We report the case of a 3-year-old boy who presented a severe form of late infantile metachromatic leukodystrophy. This patient was found to be homozygous for the arylsulfatase A pseudodeficiency. This condition is rare and can lead to a severe disease. Prenatal diagnosis was performed in this family, and the fetus was healthy.

Peripheral neuropathy as the sole initial finding in three children with infantile metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is a progressive white matter disease caused by arylsulfatase A deficiency. Demyelination in the nervous system is detected by cerebral magnetic resonance imaging (MRI) and neurophysiological studies. We present three children with infantile MLD, who had difficulties in standing and walking with absent reflexes. Protein levels in cerebral spinal fluid (CSF) were elevated and nerve conduction studies revealed slowing down of motor nerve conduction velocity. Initial cerebral MRIs showed no white matter changes. Consecutively, all three children developed clinical symptoms of neurodegenerative disease. Follow-up MRI and arylsulfatase A testing led to diagnosis of MLD. We conclude, that in young children who present with an acute/subacute demyelinating polyneuropathy, MLD is a differential diagnosis.

A spontaneously immortalized Schwann cell line to study the molecular aspects of metachromatic leukodystrophy

The arylsulfatase A (ASA)-deficient mouse is a murine model of human metachromatic leukodystrophy (MLD) caused by a genetic defect in the ASA gene. Deficiency of ASA causes accumulation of cerebroside-3-sulfate (sulfatide) in visceral organs and in the central and peripheral nervous system, which subsequently causes demyelination in these areas. To investigate further the cellular pathomechanism of MLD, we established spontaneously immortalized Schwann cell lines from ASA-deficient mice. Cells showed marked sulfatide storage in the late endosomal/lysosomal compartment. This sulfatide accumulation can be further increased by external treatment with sulfatide using a lipid based transfection reagent as a cargo. The accumulated sulfatide was degraded in response to ASA treatment and first examination revealed that alteration on the molecular level found in ASA-deficient mice can also be observed in the presented cell culture model. Hence, these cells could be a suitable model to study MLD at a molecular level.

Peripheral neuropathy in metachromatic leucodystrophy. A study of 40 cases from south India

BACKGROUND

There is a paucity of literature from India on metachromatic leucodystrophy (MLD), a rare metabolic disorder of childhood resulting from aryl sulfatase A (ASA) deficiency.Patients/

METHODS

Case records of histopathologically verified cases of MLD, evaluated over a period of 12 years at the National Institute of Mental Health and Neurosciences, Bangalore, India, were reviewed.

RESULTS

The late infantile group (36) manifested with regression of milestones (all), delayed mile stones (14), gait abnormalities (14), and seizures (11). Despite spasticity (29), there was hypo/areflexia in 25 patients. Optic atrophy (six) was rare. Consanguinity was noted in 25 children and four had a history of similar illness in siblings. Behavioural problems dominated in the juvenile group (four), but associated cognitive decline and hyporeflexia provided a clue to the diagnosis. Low serum ASA (seven of 20), raised cerebrospinal fluid protein (five of 12), and urinary metachromatic granules (two of 32) were infrequent. Electrophysiological evidence of severe demyelinating and length dependent sensory motor neuropathy was observed in all, even in the presence of hyper-reflexia. In addition to metachromatic dysmyelinating neuropathy in all patients, sural nerve biopsy in 20 patients revealed orthochromatic deposits within perivascular macrophages, particularly among those patients with normal ASA values (11 of 14), suggesting the accumulation of other glycosphingolipids.

CONCLUSIONS

This study produced some noteworthy observations: the high degree of consanguinity associated with MLD in India, the existence of MLD with normal serum concentrations of ASA, the deposition of orthochromatic lipids, and electrophysiological evidence of a partial conduction block.

Stem cells for the treatment of myelin loss

Treatment of myelin loss is particularly suited to therapeutic strategies based on cell replacement. Demyelination represents a defined and functionally debilitating deficit, and remyelination can be accomplished by supplying regions of demyelination with myelinogenic cell populations. Clinical interest in stem cells as a source of myelinogenic cells arises from their ability to provide an apparently unlimited cell supply for transplantation, and from recent demonstrations that they can be directed to myelinogenic phenotypes with high purity. Here, I present the emerging perspective that stem-cell-mediated remyelination of the adult CNS is a viable therapeutic strategy, and discuss the challenges to remyelination posed by the environment of acute and chronic injuries.

Hereditary peripheral neuropathies of childhood

PURPOSE OF REVIEW

The purpose of this review is to assist neurologists, paediatricians and other interested readers in following the expanding volume of information relating to the hereditary peripheral neuropathies of childhood.

RECENT FINDINGS

During the last year, an exciting new potential therapy for hereditary sensory and motor neuropathy has been reported, and there has been a rapid expansion in our understanding of the genetic basis of a number of dominantly and recessively inherited neuropathies of childhood, most particularly in forms with pure motor or sensory and autonomic involvement.

SUMMARY

Advances in our understanding of the molecular basis of the inherited neuropathies of childhood may provide greater insight into the pathogenesis of these disorders, hopefully identifying new therapeutic strategies for these lifelong conditions.