Adult type neuronal storage disease with neuraminidase deficiency

Abstract

We describe a patient with adult‐onset neuronal storage disease characterized by myoclonus, cerebellar ataxia, convulsive seizures, cherry‐red spots, skeletal dysplasia, mild gargoyle features, inguinal hernia, and angiokeratoma. Cytoplasmic inclusions consistent with lysosomal storage disease were demonstrated in neurons of the autonomic nervous system. Accumulation of GM₃ and GM₂ gangliosides was found in sympathetic ganglia but a catabolic disturbance of these gangliosides was ruled out by normal levels of GM₃ ganglioside sialidase and N‐acetyl‐β‐hexosaminidase A activities. β‐Galactosidase activity was decreased in leukocytes and fibroblasts, but not in serum. GM₁ gangliosidosis was ruled out by lipid analyses, and mucopolysaccharidosis by normal excretion of mucopolysaccharide in urine. Sialyl oligosaccharides were increased in urine and α‐neuraminidase was deficient in fibroblasts. This disorder is considered to be an inherited metabolic disorder of sialyl glycoproteins and oligosaccharides due to deficiency of an α‐neuraminidase.