Late Infantile Metachromatic Leukodystrophy Research Articles

Correction of Brain Oligodendrocytes by AAVrh.10 Intracerebral Gene Therapy in Metachromatic Leukodystrophy Mice

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder characterized by accumulation of sulfatides in glial cells and neurons, the result of an inherited deficiency of arylsulfatase A (ARSA; EC 3.1.6.8) and myelin degeneration in the central and peripheral nervous systems. No effective treatment is currently available for the most frequent late infantile (LI) form of MLD, which results in rapid neurological degradation and early death after the onset of clinical manifestations. To potentially arrest or reverse disease progression, ARSA enzyme must be rapidly delivered to brain oligodendrocytes of patients with LI MLD. We previously showed that brain gene therapy with adeno-associated virus serotype 5 (AAV5) driving the expression of human ARSA cDNA under the control of the murine phosphoglycerate kinase (PGK) promoter alleviated most long-term disease manifestations in MLD mice. Herein, we evaluated the short-term effects of AAVrh.10 driving the expression of human ARSA cDNA under the control of the cytomegalovirus/β-actin hybrid (CAG/cu) promoter in 8-month-old MLD mice that already show marked sulfatide accumulation and brain pathology. Within 2 months, and in contrast to results with the AAV5-PGK-ARSA vector, a single intrastriatal injection of AAVrh.10cuARSA resulted in correction of brain sulfatide storage, accumulation of specific sulfatide species in oligodendrocytes, and associated brain pathology in the injected hemisphere. Better potency of the AAVrh.10cuARSA vector was mediated by higher neuronal and oligodendrocyte transduction, axonal transport of the AAVrh.10 vector and ARSA enzyme, as well as higher CAG/cu promoter driven expression of ARSA enzyme. These results strongly support the use of AAVrh.10cuARSA vector for intracerebral gene therapy in rapidly progressing early-onset forms of MLD.

The natural course of gross motor deterioration in metachromatic leukodystrophy

Motor deterioration is a key feature in metachromatic leukodystrophy (MLD). The lack of data about its natural course impedes evaluation of therapeutic interventions. This study aimed to provide data about motor decline in MLD. Fifty-nine patients (27 males, 32 females) with MLD (21 with late-infantile MLD and 38 with juvenile MLD) were recruited within a nationwide survey (the German LEUKONET). Median (range) age at onset was 17 months (9-27) for the group with late-infantile MLD and 6 years 2 months (2y 11mo-14y) for the group with juvenile MLD. Gross motor function was assessed using the Gross Motor Function Classification for MLD. In late-infantile MLD, all patients showed loss of all gross motor function until 3 years 4 months of age. Patients with juvenile MLD showed a more variable and significantly longer motor decline (p<0.001). For a patient with the juvenile form showing first gait disturbances, the probability of remaining stable for more than 1 year was 84%, and 51% for more than 2 years. Having lost independent walking, subsequent motor decline was as steep as in the late-infantile form (median 5 mo, interquartile range 3-22). The course of motor disease was more variable in juvenile MLD with respect to onset and dynamics. However, the motor decline after the loss of independent walking was similarly steep in both forms. These data can serve as a reference for clinical studies that are topics of current research and allow definition of inclusion/exclusion criteria.

Metachromatic leukodystrophy: natural course of cerebral MRI changes in relation to clinical course

Metachromatic Leukodystrophy (MLD) is a rare disorder leading to demyelination and neurological impairment. A natural history study within the German leukodystrophy network analyzed MRI changes with respect to the clinical course. 113 MR images of 68 patients (33 late-infantile, 35 juvenile) were studied cross-sectionally and longitudinally. MRI and motor deterioration were assessed using standardized scoring systems. The temporal and spatial patterns of MR severity scores differed between the late-infantile and juvenile form. Although early (involving central white matter, corpus callosum) and late signs (involving pons, cerebellum, cerebral atrophy) were similar, high MRI scores (mean 18, SD 1.2, p < 0.001) were evident in the juvenile form already at the onset of first symptoms and even in presymptomatic patients. The progression rate of the MRI score was clearly higher and more uniform in the late-infantile (on average 8 per year, p < 0.0001) than in the juvenile patients (on average 0.4 per year, p < 0.08). In late-infantile patients, MRI changes correlated highly with motor deterioration (rho = 0.73, p < 0.001), this was less remarkable in the juvenile form (rho = 0.50, p < 0.01). Severe motor dysfunction was associated with U-fiber involvement and cerebellar changes (p < 0.05). MRI showed a typical spatial pattern, which evolved gradually and uniformly during disease progression in late-infantile MLD. In juvenile MLD MRI changes were already observed at disease onset and temporal patterns were more variable. As therapeutic options for MLD are evolving, these findings are not only important for patient counseling but also for the evaluation of therapeutic interventions.

Intestinal Involvement in Metachromatic Leukodystrophy

Metachromatic leukodystrophy is a lysosomal storage disease caused by the deficiency of the enzyme arylsulfatase A. If arylsulfatase A is deficient, sulfatide accumulates. Functionally, this accumulation results in progressive neurological deterioration. The reports about the extra nervous system manifestations of metachromatic leukodystrophy are related to the gallbladder involvement such as polyposis. Unexplained vomiting began in a 5&frac12;-year-old girl with late infantile metachromatic leukodystrophy. Endoscopy showed multiple polypoid masses in the pylor of the stomach and duodenum. Severe gastrointestinal bleedings occurred during nasogastric feeding. Intestinal intussusception developed later. To the authors' knowledge, intestinal polypoid masses and obstruction with metachromatic leukodystrophy have not previously been reported. The persistent vomiting may be a symptom of intestinal obstruction due to intestinal polypoid masses with metachromatic leukodystrophy. There may be a trend for the development of polypoid masses in intestine as well as in the gallbladder in metachromatic leukodystrophy.

Brain N -acetylaspartate levels correlate with motor function in metachromatic leukodystrophy

Late infantile metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disorder that causes severe demyelination of the nervous system. The neuronal metabolite N-acetylaspartate (NAA) serves as a source of acetyl groups for myelin lipid synthesis in oligodendrocytes and is known as a marker for neuronal and axonal loss. NAA and other metabolite levels measured by proton magnetic resonance spectroscopy (MRS) correlate with performance of the brain in normal children. There is a need for sensitive measures of disease progression in patients with MLD to enable development of future treatments. A cross-section of 13 children with late infantile MLD were examined by proton MRS. Signals from NAA, total choline, and total creatine in the deep white matter were measured and correlated with the results of cognitive and motor function tests. The NAA signal decreased as the disease process advanced. Motor function, measured by the Gross Motor Function Measure-88, varied from 13 (only head movement in the supine position) to 180 (able to walk) across the study cohort, demonstrating a wide range in functional status. Similarly, varied decreases were observed in cognitive function. We report strong positive correlations between standardized measures of motor and cognitive function and NAA levels in the deep white matter. We suggest that NAA levels could serve as a sensitive biomarker in children with MLD. Proton MRS may provide a valuable tool for measuring the effects of treatment interventions in this disorder.

Hematopoietic Stem Cell Therapy In Eight Patients with Metachromatic Leukodystrophy – Relevance of Post-Transplant Medication.

AbstractAbstract 3727The lysosomal storage disease metachromatic leukodystrophy (MLD) is caused by mutations in the arylsulfatase A (ASA) gene leading to demyelination in the central nervous system (CNS). Children often present impaired motor skills and progress to an inability to walk, paresis and cognitive deterioration. Therapeutic options are limited and currently focus on enzyme replacement, gene therapy and hematopoietic stem cell transplantation (HSCT). Both, gene therapy and HSCT aim to establish a continuous endogenous supply of ASA, which can be taken up by somatic cells of the recipient to correct their own lysosomal metabolism.We analyzed 8 patients with MLD, who underwent HSCT between 7 months and 15 years of age, regarding toxicity of a reduced intensity condition regimen and GvHD prophylaxis. The mean follow up was 2.8 years (range 8 months to 9.5 years). All patients received conditioning with treosulfan (3 × 14 g/m2), fludarabin (4 × 40 mg/m2) and thiotepa (10 mg/kg). Six patients received bone marrow from a 10/10 matched unrelated donor, one patient from her brother and one patient with late infantile MLD was transplanted from her haploidentical mother. Patients received a mean dose of 7.74 × 106 CD34+ cells/kg BW and engrafted at day 12 (range d11 to d22) with permanent full donor chimerism. Organ toxicity reached mucositis grade III and skin grade I. Three patients developed transient acute graft-versus-host disease (GvHD) of the skin grade II, which responded well to steroids. There was no case of transplant-related mortality and no chronic GvHD. The relative ASA activity in peripheral blood mononuclear cells (PBMCs) pre-transplantation was between 0 and 0.11 A514nm/106 cells and after transplantation between 0.52 and 2.24 A514nm/106 cells. Patients who were asymptomatic prior to transplantation stayed asymptomatic, but those who presented with neurological symptoms showed various degrees of progression. As the conditioning regimen showed no immediate neurotoxicity, we asked if other drugs may account for the disease progression early after transplantation. Cyclosporine A (CsA) is commonly used as post-transplant GvHD prophylaxis and is known for neurotoxic side effects. Thus, we analyzed effects of CsA on the activity of ASA in comparison to tacrolimus or mycophenolic acid (MPA). PBMCs were cultured with and without 75 or 150 ng/ml CsA (pharmacological level) for 8 days. During this time period, the ASA activity decreased to 70% of the activity of PBMC without CsA treatment. By contrast, the ASA activity of PBMCs did not decrease under treatment with pharmacological levels of tacrolimus (7,5 or 15 ng/ml) and MPA (3 or 7,5 μg/ml). Cell viability and metabolic activity were comparable in the presence of CsA and tacrolismus as assessed by MTS assays. This implies that the decrease of the ASA activity was not due to direct cell toxicity of CsA.Taken together, the conditioning regimen was well tolerated with low toxicity and good engraftment. HSCT is an option for treatment of asymptomatic MLD patients, whereas further studies are needed to identify symptomatic patients who may still benefit from the procedure. Here, the choice of GvHD prophylaxis may be an important factor. In vitro data suggested that CsA should be reconsidered with regimens including tacrolimus or mycophenolate mofetil as an alternative. Disclosures:No relevant conflicts of interest to declare.

Clinical and biochemical study of 29 Brazilian patients with metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is a lysosomal disorder caused by arylsulfatase A (ARSA) deficiency. It is classified into three forms according to the age of onset of symptoms (late infantile, juvenile, and adult). We carried out a cross-sectional and retrospective study, which aimed to determine the epidemiological, clinical, and biochemical profile of MLD patients from a national reference center for Inborn Errors of Metabolism in Brazil. Twenty-nine patients (male, 17) agreed to participate in the study (late infantile form: 22; juvenile form: 4; adult form: 1; asymptomatic: 2). Mean ages at onset of symptoms and at biochemical diagnosis were, respectively, 19 and 39 months for late infantile form and 84.7 and 161.2 months for juvenile form. The most frequently reported first clinical symptom/sign of the disease was gait disturbance and other motor abnormalities (72.7%) for late infantile form and behavioral and cognitive alterations (50%) for juvenile form. Leukocyte ARSA activity level did not present significant correlation with the age of onset of symptoms (r = -0.09, p = 0.67). Occipital white matter and basal nuclei abnormalities were not found in patients with the late infantile MLD. Our results suggest that there is a considerable delay between the age of onset of signs and symptoms and the diagnosis of MLD in Brazil. Correlation between ARSA activity and MLD clinical form was not found. Further studies on the epidemiology and natural history of this disease with larger samples are needed, especially now when specific treatments should be available in the near future.

Identification of a new Arylsulfatase A ( ARSA) gene mutation in Tunisian patients with metachromatic leukodystrophy (MLD)

Metachromatic leukodystrophy (MLD) is an autosomal recessive, lysosomal storage disease caused by a deficiency of the enzyme arylsulfatase A (ARSA). The aim of the present study was to identify the molecular basis of MLD in Tunisian population. Two Tunisian patients with late infantile MLD were studied. Both patients were homozygous for a new missense mutation that causes a substitution of Trp in Gly p.W124G. This is the first mutation of ARSA gene described in Tunisian population.

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.

Molecular and clinical consequences of novel mutations in the arylsulfatase A gene

Metachromatic leukodystrophy (MLD), a severe neurodegenerative metabolic disorder, is caused by deficient activity of arylsulfatase A (ARSA; EC 3.1.6.8), which leads to a progressive demyelinating process in central and peripheral nervous systems. In this study, a DNA sequence analysis was performed on six Polish patients with different types of MLD. Six novel mutations were identified: one nonsense (p.R114X), three missense (p.G122C, p.G293C, p.C493F) and two frameshift mutations (g.445_446dupG and g.2590_2591dupC). Substitutions p.G293C and p.C493F and duplication g.445_446dupG caused a severe reduction of enzyme activity in transient transfection experiments on mammalian cells (less than 1% of wild-type (WT) ARSA activity). Duplication 2590_2591dupC preserved low-residual ARSA activity (10% of WT ARSA). In summary, the novel MLD-causing mutations in the exons 2, 5 and even in 8 of the ARSA gene described here can be classified as severe type 0, leading in homozygosity to the late infantile form MLD. Growth retardation, delayed motor development, gait disturbances, tonic-clonic seizures and non-epileptic muscle spasms were the first onset symptoms in patients with late infantile form of MLD. In individual with juvenile type MLD gait disturbances evidenced the onset of the disease, while in a patient with late juvenile MLD, difficulties at school were displayed.

Early marrow transplantation in a pre-symptomatic neonate with late infantile metachromatic leukodystrophy does not halt disease progression

Early marrow transplantation in a pre-symptomatic neonate with late infantile metachromatic leukodystrophy does not halt disease progression

Novel mutations in the arylsulfatase A gene in eight Italian families with metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by arylsulfatase A (ARSA) deficiency. We analysed the ARSA gene in eight unrelated Italian families with different clinical variants of MLD and identified three novel mutations: two Ser406Gly, (Glu329Ter) associated with late infantile MLD and one (Leu52Pro) with juvenile MLD. Only one family carried a pseudodeficiency allele (Asn350Ser). The IVS2 + 1G > A mutation occurred in four families. We also identified three polymorphisms, all in heterozygosis: Thr391Ser was present in five families, Trp193Cys in four families, and Ala210Ala in one family. We could identify 100% of the alleles causing MLD in the families, involving 12 different mutations, resulting in improved prognosis and genetic counselling.

Mutations c.459 + 1G > A and p.P426L in the ARSA gene: Prevalence in metachromatic leukodystrophy patients from European countries

In this multicentre study, we examined the prevalence of two mutations in the arylsulfatase A (ARSA) gene, i.e., c.459 + 1G > A and p.P426L, in 384 unrelated European patients presenting with different types of metachromatic leukodystrophy (MLD). In total, c.459 + 1G > A was found 194 times among the 768 investigated ARSA alleles (25%), whereas p.P426L was identified 143 times (18.6%). Thus, these two mutations accounted for 43.8% of investigated MLD alleles. Mutation c.459 + 1G > A was most frequent in late-infantile MLD patients (40%), while p.P426L was most frequent in adults (42.5%), which is consistent with earlier observations, although p.P426L was also found in a few late-infantile patients (0.9%), and c.459 + 1G > A was present in some adults (9%). Mutation c.459 + 1G > A is more frequent in countries situated at the western edges of Europe, i.e., in Great Britain and Portugal, and also in Belgium, Switzerland, and Italy, which is visible as a strand ranging from North to South, and additionally in Czech and Slovak Republics. Mutation p.P426L is most prevalent in countries assembled in a cluster containing the Netherlands, Germany, and Austria. In other Central European countries, the frequency of both c.459 + 1G > A and p.P426L ranges from 8 to 37.5%. Our study has confirmed that c.459 + 1G > A and p.P426L are the most frequently found MLD-causing mutations in Europe. The data about their prevalence reflect the population variability in Europe.

Spinal cord and cauda equina MRI findings in metachromatic leukodystrophy: case report

Metachromatic leukodystrophy (MLD) is an autosomal recessive disease with well-documented intracranial findings on neuroimaging both by computed tomography (CT) and MRI. We describe the first case of late infantile MLD with spinal involvement revealed by MRI as marked contrast enhancement of nerve roots at the level of the cauda equina.

ASA E382K disrupts a potential exonic splicing enhancer and causes exon skipping, but missense mutations in ASA are not associated with ESEs.

Metachromatic leukodystrophy (MLD) is an autosomal recessive disorder caused by mutations in the arylsulfatase A (ASA) gene. We identified a Thai boy with typical late-infantile MLD and found that he was a compound heterozygote for a novel mutation, g.IVS3-2A>G causing c.679-696del inherited from his father, and a previously reported missense mutation, g.1144G>A causing c.1102-1204del inherited from his mother. The g.1144G>A mutation was located in the middle of exon 7 and previously assumed to be deleterious by causing an amino acid change, E382K. We, herein, found that its actual pathogenic effect was splicing-related by disrupting a potential exonic splicing enhancer (ESE) and causing a complete exon 7 skipping. This is the first missense mutation in the ASA gene that is deleterious from disrupting a potential ESE. The results prompted us to investigate pathogenic effects of other reported missense mutations in the ASA gene. Unlike pathogenic missense mutations in some other genes, those in the ASA gene do not colocalize with ESE sites suggesting that pathogenic effects of majority of them are not splicing-related.

An unusual arylsulfatase A pseudodeficiency allele carrying a splice site mutation in a metachromatic leukodystrophy patient.

A late infantile metachromatic leukodystrophy patient was found to be heterozygous for the arylsulfatase A (ARSA) pseudodeficiency (pd) polyadenylation site variant ((*)96A>G) in the absence of the commonly associated N-glycosylation site variant (N350S). ARSA alleles were sequenced and the genotype completely defined. Six sequence variations were identified, among which two resulted as severe disease-causing mutations, both leading to the loss of the reading frame: a splice acceptor site mutation in intron 4 (849-1G>A), located on the (*)96A>G allele and a mononucleotide deletion (258delC) in exon 2, located on the other allele. The altered splicing caused by the 849-1G>A mutation was shown by in vitro expression of a recombinant gene containing the genomic region surrounding the mutation. Haplotype analysis of the unusual pd allele was performed in order to investigate its possible origin.

Contribution of arylsulfatase A mutations located on the same allele to enzyme activity reduction and metachromatic leukodystrophy severity.

The occurrence of different mutations on the same arylsulfatase A allele is not uncommon, due to the high frequency of several variants, among which the pseudodeficiency mutations are particularly important. We identified a late infantile metachromatic leukodystrophy patient carrying on one allele the new E253K mutation and the known T391S polymorphism, and on the other allele the common P426L mutation, usually associated with the adult or juvenile form of the disease, and the N350S and *96A>G pseudodeficiency mutations. To analyze the contribution of mutations located on the same allele to enzyme activity reduction, as well as the possible phenotype implications, we performed transient expression experiments using arylsulfatase A cDNAs carrying the identified mutations separately and in combination. Our results indicate that mutants containing multiple mutations cause a greater reduction of ARSA activity than do the corresponding single mutants, the total deficiency likely corresponding to the sum of the reductions attributed to each mutation. Consequently, each mutation may contribute to ARSA activity reduction, and, therefore, to the degree of disease severity. This is particularly important for the alleles containing a disease-causing mutation and the pseudodeficiency mutations: in these alleles pseudodeficiency could play a role in affecting the clinical phenotype.

Epileptic seizures and electroencephalographic evolution in genetic leukodystrophies.

The purpose of this study is to explore and compare epileptic seizures and EEG evolution in the various types of genetic leukodystrophy (GL). The authors reviewed the medical records and analyzed 69 serial EEGs in 27 patients with GLs: 13 with late infantile metachromatic leukodystrophy, one with juvenile metachromatic leukodystrophy, one with globoid cell leukodystrophy, six with X-linked childhood adrenoleukodystrophy, one with neonatal adrenoleukodystrophy, four with classic Pelizaeus-Merzbacher disease (PMD), and 1 with connatal Pelizaeus-Merzbacher disease. The diagnoses were made by biochemical and molecular studies. Two or more EEG studies with both awake and sleep traces were recorded during the varying clinical stages for each patient. At the beginning of the GLs, the EEGs were normal or showed mild slowing of background activity. Clinical seizures, mainly of focal origin, with progressive slowing and paroxysmal discharges on EEGs, usually appeared during the later stages of metachromatic leukodystrophy, X-linked childhood adrenoleukodystrophy, and classic Pelizaeus-Merzbacher disease. However, intractable seizures, mainly generalized in nature, and more severe slowing and abundant paroxysmal discharges on EEGs, with commensurate neurologic deterioration, were observed during the earlier course of globoid cell leukodystrophy, neonatal adrenoleukodystrophy, and connatal Pelizaeus-Merzbacher disease. These results indicate that GLs involve not only white matter, but gray matter as well. In all types of GL, there is good correlation between the severity of EEG changes, the severity of the diseases, and the clinical state of the patient.

Neurophysiology and MRI in late-infantile metachromatic leukodystrophy

We present serial clinical, radiologic, and neurophysiologic findings of a patient with late-infantile metachromatic leukodystrophy who was first admitted at 30 months of age because of gait disturbance. The neurologic findings were consistent with mild spastic diplegia (occasionally with toe walking). Magnetic resonance imaging disclosed diffuse high intensity in the cerebral white matter on T 2-weighted images. Nerve conduction velocity studies and evoked-potential studies were markedly abnormal. Assay of arylsulfatase A activity in leukocyte culture disclosed a marked deficiency of the enzyme, confirming the diagnosis of late-infantile metachromatic leukodystrophy. Serial neurophysiologic studies demonstrated a marked decrease of nerve conduction velocities, both motor and sensory, as well as prolongation or disappearance of brainstem auditory-, visual-, and somatosensory–evoked potential latencies. Magnetic resonance imaging studies revealed initially diffuse increased signal intensity of periventricular and subcortical white matter on T 2-weighted images, progressing to cortical atrophy with involvement of the arcuate fibers and the cerebellar white matter, correlating with the clinical deterioration (severe spastic tetraplegia with optic atrophy and epilepsy).

Occurrence, distribution, and phenotype of arylsulfatase A mutations in patients with metachromatic leukodystrophy

Occurrence, distribution, and phenotype of arylsulfatase A (ASA) mutations were investigated in 27 patients with metachromatic leukodystrophy (MLD) from Central Europe, mainly from Austria (n = 15) and Poland (n = 9). Genomic DNA from leukocytes, fibroblasts, or paraffin-embedded, formalin-fixed brain or nerve tissue, respectively, was tested by natural or mutated primer-modulated PCR restriction, fragment length polymorphism for the eight most common European mutations: R84Q, S96F, 459+1G > A, I179S, A212V, 1204+1G > A, P426L, and 1401del11bp. The overall identification rate of unrelated MLD alleles was the highest, in adult (90%), medium in juvenile (50%), and lowest in late infantile (36%) MLD patients. The two common alleles, 459+1G > A and P426L, together accounted for 42% of all 50 unrelated MLD alleles investigated; I179S was observed in 6 of 50 MLD alleles (12%). Thus, I179S was far more frequent than hitherto thought and appears to be a third common mutation in Europe. Moreover, a different allelic distribution between Austrian and Polish juvenile patients was disclosed, indicating genetic heterogeneity of MLD even within Central Europe. The genotype-phenotype correlation suggested by Polten et al. [N Engl J Med 324:18-22, 1991] was not followed by all of our MLD patients. Moreover, some MLD patients with identical ASA mutations presented with different phenotypes. This may be due, at least in some cases, to the presence of an additional mutation on individual mutant alleles. Therefore, prediction of the clinical course from single mutation analysis is not possible.