Abstract
One patient presented at 3 months with Hurler facies, hepatomegaly, hypotonia, developmental retardation, lumbar beaking, and normal urinary mucopolysaccharides. The second patient presented at 23 months with progressive psychomotor deterioration, spasticity, lumar beaking, but no hurler features, organomegaly or mucopolysacchariduria. B-galactosidasc activity was virtually absent in WBC and fibroblasts in both patients.
Biopsied liver tissue showed striking morphologic and enzymatic differences. the early onset liver was enlarged, firm, and histologically showed marked vacuolozation of most hepatocytes. The late onset liver was normal grossly and histologically. B-galactosidasc activities were measured and expressed as nmoles of p-nitropheny-B-D-galactopyranoside hydrolyzed/min/mg protein. Enzyme activity in normal livers showed a pH optimum of 4.0–4.5, while the pH optimum was 6.5 in both patients. Activity at pH 6.5 was strikingly clevated in the late onset case (21.8) while the early onset patients (1.5) was below normal (2.0–5.2). Starch gelelectrophoresis of normal liver showed one fast and two slow isozymes. In both patients only a single rapidly moving isozyme was visualized.
These patients despite distinctly different clinical phenotypes showed similar pH optima and isozymic patterns implying a similar gene mutation. We are currently studying the possibility that differences in visceral storage in the early and late GM1 gangliosidoses may be related to the activity of the pH 6.5 isozyme.
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Singer, H., Schafer, I. & Schwartz, R. Clinical and Enzymatic Variation in GM1 Gangliosidosis. Pediatr Res 4, 438 (1970). https://doi.org/10.1203/00006450-197009000-00019
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DOI: https://doi.org/10.1203/00006450-197009000-00019