1/67. Slow progression of juvenile metachromatic leukodystrophy 6 years after bone marrow transplantation.Metachromatic leukodystrophy refers to a group of genetic neurologic diseases caused by deficiencies of the enzyme arylsulfatase A and the resulting accumulation of sulfatides in white matter. bone marrow transplantation has been advocated as a treatment in an attempt to correct the enzyme deficiency. Such a transplant was performed in 1991 in a 16-year-old girl with a form of late juvenile metachromatic leukodystrophy caused by a homozygous P426L mutation in the arylsulfatase A gene. Engraftment was prompt and resulted in constant enzymatic normalization of circulating lymphocytes. The elevated urinary excretion of sulfatides remained unaffected. Clinical findings up until transplantation consisted of gait disturbances, impairment of cognitive functioning, and deterioration in school performance over several years. During a 6-year follow-up period, the patient's condition was subject to major fluctuations but, on the whole, findings showed slow neurologic and neurophysiologic deterioration. The clinical course observed after bone marrow transplantation probably more or less reflects the natural course expected in this form of late-onset metachromatic leukodystrophy.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
2/67. Metachromatic leucodystrophy: a newly identified mutation in arylsulphatase A, D281Y, found as a compound heterozygote with I179L in an adult onset case.The majority of mutations identified in patients with Metachromatic leucodystrophy are unique to individual families. We report here a new mutation in the arylsulphatase A gene (D281Y) identified in a patient with late-onset Metachromatic leucodystrophy. This mutation was inherited in cis with the common pseudo-deficiency allele and in trans with the previously described I179S (250100.0008) mutation which complicated the enzymatic diagnosis of this condition. Sequence comparison shows D281 to be highly conserved amongst the arylsulphatases. The clinical features of this patient which are predominantly of a slowly progressive psychiatric and intellectual deterioration rather than rapid neurological impairment are typical of I179S compound heterozygotes.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
3/67. 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 T2-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 T2-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).- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
4/67. A non-glycosylated and functionally deficient mutant (N215H) of the sphingolipid activator protein B (SAP-B) in a novel case of metachromatic leukodystrophy (MLD).The lysosomal degradation of sphingolipids with short oligosaccharide chains depends on small glycosylated non-enzymatic sphingolipid activator proteins (SAPs, saposins). Four of the five known SAPs, SAP-A, -B, -C and -D, are derived by proteolytic processing from a common precursor protein (SAP-precursor) that is encoded by a gene on chromosome 10 consisting of 15 exons and 14 introns. SAP-B is a non-specific glycolipid binding protein that stimulates in vitro the hydrolysis of about 20 glycolipids by different enzymes. In vivo SAP-B stimulates in particular the degradation of sulphatides by arylsulphatase A. So far, four different point mutations have been identified on the SAP-B domain of the SAP-precursor gene. The mutations result in a loss of mature SAP-B, causing the lysosomal accumulation of sulphatides and other sphingolipids, resulting in variant forms of metachromatic leukodystrophy (MLD). Here we report on a patient with SAP-B deficiency that is caused by a new homoallelic point mutation that has been identified by mRNA and dna analysis. A 643A > C transversion results in the exchange of asparagine 215 to histidine and eliminates the single glycosylation site of SAP-B. Metabolic labelling experiments showed that the mutation had no effect on the intracellular transport of the encoded precursor to the acidic compartments and its maturation in the patient's cells. All four SAPs (SAP-A to SAP-D) were detectable by immunochemical methods. SAP-B in the patient's cells was found to be slightly less stable than the protein in normal cells and corresponded in size to the deglycosylated form of the wild-type SAP-B. Feeding studies with non-glycosylated SAP-precursor, generating non-glycosylated SAP-B, showed that the loss of the carbohydrate chain reduced the intracellular activity of the protein significantly. The additional structural change of the patient's SAP-B, caused by the change of amino acid 215 from asparagine to histidine, presumably resulted in an almost completely inactive protein.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
5/67. Characterization of four arylsulfatase A missense mutations G86D, Y201C, D255H, and E312D causing metachromatic leukodystrophy.Metachromatic leukodystrophy is a lysosomal storage disease caused by the deficiency of arylsulfatase A. Here we describe a hitherto unknown arylsulfatase A allele carrying a E312D missense mutation and characterize the effects of this and three previously described missense mutations, G86D, Y201C, and D255H, on arylsulfatase A. In transfection experiments no enzyme activity can be expressed from arylsulfatase A cDNAs coding for the D255H substituted enzyme, whereas Y201C and E312D mutations were associated with low amounts of residual enzyme activity. All amino acid substitutions lead to a decreased stability of the mutant enzyme, and metabolic labeling experiments indicated that except for the E312D substitution the mutations cause arrest of the mutant arylsulfatase A polypeptides in a prelysosomal compartment.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
6/67. sneddon syndrome, arylsulfatase A pseudodeficiency and impairment of cerebral white matter.We describe a 11 year-old-boy with sneddon syndrome, confirmed by skin biopsy, and MR evidence of diffuse cerebral hyperintensity of white matter; he also suffered from pre-perinatal hypoxic-ischemic distress. Arylsulfatase A activity was found reduced because of arylsulfatase A pseudodeficiency. We suggest that the association of pre-perinatal distress, sneddon syndrome and arylsulfatase A pseudodeficiency is responsible for the diffuse impairment of cerebral white matter, never reported in sneddon syndrome and similar to described cases of delayed posthypoxic demyelination and arylsulfatase A pseudodeficiency.- - - - - - - - - - ranking = 7keywords = deficiency (Clic here for more details about this article) |
7/67. Unusual clinical presentation in two cases of multiple sulfatase deficiency.Multiple sulfatase deficiency (MSD) is an inborn error of metabolism that combines the clinical features of late infantile metachromatic leukodystrophy and mucopolysaccharidosis. The characteristic biochemical abnormality is a reduction in the activities of several sulfatases, with consequent tissue accumulation of sulfatides, sulfated glycosaminoglycans, sphingolipids, and steroid sulfates. In this study we present two unusual cases of MSD with variable enzymatic deficiency of arylsulfatases A, B, and C. Both patients had ichthyosis, broad thumbs and index fingers, an unusually slow progression of the neurologic symptoms, and lacked the hepatosplenomegaly that is typical of MSD. Olivopontocerebellar atrophy was present and one patient had a large retrocerebellar cyst. Mucopolysaccharides were not detected in the urine from either subject. Leukocyte arylsulfatase A activity in patient 1 was 0.46 nmol/mg protein/hr and in patient 2 was 0.0 nmol/mg protein/hr (normal 0.7-5.0 nmol/mg protein/hr). Leukocyte arylsulfatase B activity in patient 1 was 24 nmol/mg protein/hr and in patient 2 was 22 nmol/mg protein/hr (normal 115-226 nmol/mg protein/hr). Leukocyte arylsulfatase C in patient 1 was 0.30 pmol/mg protein/hr and in patient 2 was 0.28 pmol/mg protein/hr (normal 0.84 pmol/mg protein/hr). In conclusion, these two patients with MSD had mild clinical presentations not previously reported and variable enzymatic deficiency of arylsulfatases A, B, and C.- - - - - - - - - - ranking = 7keywords = deficiency (Clic here for more details about this article) |
8/67. Metachromatic leukodystrophy and nonverbal learning disability: neuropsychological and neuroradiological findings in heterozygous carriers.Metachromatic leukodystrophy (MLD) is an autosomal recessive neurodegenerative disorder due to deficiency of the enzyme arylsulfatase A that leads to progressive, diffuse demyelination. The syndrome of nonverbal learning disability has been attributed to white matter abnormality and has been reported in children with this disorder and in some healthy family member carriers of gene. We examined the neuropsychologic profiles and MRIs of eight members of the family of a 7-year-old girl with this disease, all of whom were heterozygous carriers of the mutation and five of whom were also carriers of the MLD pseudodeficiency gene. All had low normal levels of arylsulfatase A, and seven of the eight had average or better profiles across all assessed neuropsychological domains. The patient's younger sister had a profile with features of the syndrome of nonverbal learning disability despite a normal MRI, whereas two members with minor white matter findings did not. This family does not provide evidence for the syndrome of nonverbal learning disability in heterozygous carriers of the gene for MLD, even when associated with the MLD pseudodeficiency gene.- - - - - - - - - - ranking = 3keywords = deficiency (Clic here for more details about this article) |
9/67. Isolated peripheral neuropathy in atypical metachromatic leukodystrophy: a recurrent mutation.BACKGROUND: Metachromatic leukodystrophy (MLD) is a genetic neurodegenerative disorder resulting from a deficiency of arylsulfatase A. Late onset forms are relatively rare. central nervous system (CNS) involvement is characteristic at all ages. methods: A patient in her late 40s with peripheral neuropathy was assessed by EEG, evoked potentials, CT and nerve conduction studies. Nerve and muscle biopsy samples were investigated by electron microscopy. Arylsulfatase A activity in leukocytes and excreted cerebroside sulfate were determined. The arylsulfatase A gene was investigated for mutations using polymerase chain reaction (PCR) and dna sequencing. The identified mutation was expressed transiently in African green monkey kidney (COS) cells to determine the effect of the mutation on arylsulfatase A activity. RESULTS: central nervous system functions were normal. Nerve conduction velocities were decreased. sural nerve biopsy showed inclusions typical of MLD. Arylsulfatase A was less than 5% of normal. A homozygous mutation thr286pro was identified in the arylsulfatase A gene and demonstrated to be deleterious through transient expression studies. CONCLUSIONS: Our patient has a progressive peripheral neuropathy but has apparently intact CNS function at her present age of 57 years. Biochemical, physiological and pathological findings are consistent with a diagnosis of MLD. A homozygous mutation, thr286pro, found in her arylsulfatase A gene, decreased enzyme activity to a level consistent with a late onset form of MLD.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
10/67. The functional consequences of mis-sense mutations affecting an intra-molecular salt bridge in arylsulphatase A.Metachromatic leukodystrophy is a lysosomal storage disorder caused by the deficiency of arylsulphatase A. We describe the functional consequences of three mis-sense mutations in the arylsulphatase A gene (Asp-335-Val, Arg-370-Trp and Arg-370-Gln), affecting an apparent intramolecular Asp-335 to Arg-370 salt bridge, and interpret the effects and clinical consequences on the basis of the three-dimensional structure of arylsulphatase A. Asp-335-Val and Arg-370-Trp substitutions each cause a complete loss of enzyme activity and are associated with the most severe form of the human disease, whereas the Arg-370-Gln-substituted enzyme retains some residual activity, being found in a patient suffering from the milder juvenile form of the disease. Detailed analysis reveals that formation of the apparent salt bridge depends critically on the presence of aspartic acid and arginine residues at positions 335 and 370, respectively. Substitution by various other amino acids, including glutamic acid and lysine, affects enzyme function severely. Biosynthesis and immunoprecipitation studies indicate that the Asp-335-Val substitution affects folding of arylsulphatase A more severely than either the Arg-370-Trp or Arg-370-Gln substitutions. in vitro mutagenesis data show that clinical severity correlates with the space occupied by residue 370. The combination with structural data suggests that the bulky tryptophan residue broadens the cleft held together by the apparent salt bridge, whereas the smaller glutamine residue still allows the cleft to close, yielding a less severely affected enzyme. The position of residue 370 in the three-dimensional structure of the enzyme provides a plausible explanation for the differing severities in loss of enzyme function caused by the mutations and thus the clinical phenotype.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
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