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Potential damage of central and peripheral nervous system expressed as micro-organic brain damage (MOBD) was investigated in 27 unrelated heterozygotes with metachromatic leukodystrophy (MLD). Arylsulfatase A (ARSA) was determined in peripheral blood leukocytes and sulfatide excretion was estimated in 24-hour urine collections. Genomic DNA was analyzed for the ARSA pseudodeficiency (PD) allele by a PCR method. Clinical investigations included examination of hyper-reflexia, Babinski reflex, Wechsler Adult Intelligence Scale, Benton test, evoked potentials, and nerve conduction velocity (NCV). In our study, a higher incidence of evident or possible micro-organic brain damage was observed in true MLD/PD and MLD heterozygotes (NO/MLD, where NO means the wild allele) than in controls. On the basis of the Benton test, MOBD was suggested or indicated in 67% of MLD heterozygotes, 50% of MLD/PD heterozygotes, and 26% of controls. In our small group of carriers with MLD and PD mutations, persons NO/MLD(PD) with one wild-type allele did not show MOBD and displayed higher ARSA/beta-galactosidase ratios, unlike true MLD/PD compound heterozygotes who carry MLD-causing mutation in one allele and the ARSA-PD polymorphism in the second. Theoretically, this is a shift from autosomal recessive to autosomal dominant-like inheritance, especially when one cannot exclude the influence of polymorphisms (like ARSA-PD) in the wild allele. Since all psychological tests were age-matched, it can be assumed that the MOBD observed in MLD carriers does not have a progressive character unlike in MLD patients. However, it should be mentioned that MOBD appears to have no overt clinical consequences., (Copyright 2002 Wiley-Liss, Inc.)

Arylsulfatase A (ARSA) deficiency is the main cause of metachromatic leukodystrophy (MLD), a lysosomal disorder with no specific treatment. In view of the importance of genetic counseling, analyses of mutations and polymorphisms, including the ARSA pseudodeficiency allele, were carried out in 18 unrelated Spanish MLD patients. A systematic search allowed us to identify 100% of the alleles involving 17 different mutations, 12 of which are novel: G32S, L68P, R84W, P94A, G99V, P136S, W193X, H227Y, R288H, G308D, T327I, and IVS6-12C-->G. Two new polymorphisms, 2033C>T and 2059C>T, were identified in intron 6 which, in combination with two polymorphisms previously described (2161C>G and 2213C>G), gave rise to four different haplotypes in the control population. In addition, we also studied polymorphism 842G>T. Linkage disequilibrium was detected between mutations IVS2+1G-->A, D255H, and T327I and specific haplotypes, suggesting a unique origin for these mutations. Moreover, mutation T327I was always associated with the T allele of the new rare variant A210A (893C>T). The distribution of mutation D255H (frequency 19.4%) among patients with different MLD clinical presentation revealed a clear genotype-phenotype correlation paralleling that reported for mutation IVS2+1G-->A (frequency 25%). Among the novel mutations, only P136S and R288H occurred on a background of the ARSA pseudodeficiency allele. Screening 182 normal chromosomes identified a frequency of 8.8% of this allele; moreover, we identified two unrelated subjects with the polyA- mutation in the absence of the N350S mutation, and this infrequent haplotype reinforced the heterogeneity of conditions with ARSA deficiency., (Copyright 1999 Wiley-Liss, Inc.)

Sulfatide excretion in urine and arylsulfatase A (ASA) activity in leukocytes were determined in 10 homozygotes of metachromatic leukodystrophy (MLD), 7 obligate and 5 facultative MLD heterozygotes, 6 low ASA subjects (not related to MLD homozygotes), and in 9 controls. As compared to controls (sulfatides: 0-2 nmol/mg lipid; ASA: 101-287 nmol p-nitrocatechol/mg protein/hr), MLD homozygotes displayed highly increased sulfatide excretions (27-280 nmol) and low residual ASA activities (0-13 nmol). Of 12 MLD heterozygotes (ASA: 18-87 nmol) 10 showed increased sulfatides (3-24 nmol). All heterozygotes with ASA activity < 60 nmol (n = 8) had elevated sulfatide excretions (4-24 nmol). Thus, reduction of ASA activity below 40% of the mean value of controls seems to be the critical threshold for elevated sulfatide excretion in MLD heterozygotes. The low ASA subjects (ASA in the heterozygote range) excreted sulfatides in the control range, even those with ASA activities < 60 nmoles (n = 3; including a definite homozygote for ASA-pseudodeficiency; ASA:25 nmol). Statistical evaluation of sulfatide excretion and ASA activity in all subjects (n = 37) revealed a significant inverse relation (Spearman rank correlation; R = 0.8278, P < 0.001). The finding of elevated sulfatide excretion in certain MLD heterozygotes might point to increase of sulfatides also in the nervous system.

In a child with enzymatically and histopathologically proven metachromatic leukodystrophy (MLD), the disease pursued a course typical of juvenile MLD characterized by neurological degeneration beginning at age 9 years and ending in death at age 18. A younger brother of the patient was found to have profound deficiency of arylsulfatase A in leukocytes and to excrete five- to 20-fold greater-than-normal amounts of sulfatide in the urine. He was completely free of symptoms attributable to MLD until age 16 when he developed acute cholecystitis caused by sulfatide accumulation in the gallbladder. Results of detailed neurological examination at age 21 years were normal; formal psychometric assessment showed a full-scale IQ of 105 (Wechsler). Studies on cultured skin fibroblasts from the brother showed defects in arylsulfatase A activity, measured with the use of synthetic and natural substrates, and in radiolabeled sulfatide turnover. Cellulose acetate gel electrophoresis of fibroblast extracts from the patient showed no detectable arylsulfatase A isozyme under conditions that clearly distinguished pseudo-arylsulfatase A deficiency from classical MLD. Biochemically, the patient was indistinguishable from patients with classical MLD; on the other hand, his clinical course is dramatically more benign than that of his sister who was affected with severe MLD.