Sialidase (α‐N‐acetyl neuraminidase) deficiency: the enzyme defect in an adult with macular cherry‐red spots and myoclonus without dementia

Abstract
A 31 yr old male is described who has macular cherry-red spots, increased deep tendon reflexes and myoclonus without dementia. An older brother died at age 33 of a disease with similar symptomatology. Homogenates of cultured fibroblasts from the patient exhibited 2.6, 8.1 and 12.4% of normal mean sialidase (neuraminidase, N-acetyl-neuraminosyl glycohydrolase, EC 3.2.1.18) activity, respectively, against 2-(3''methoxyphenyl)-N-acetyl-.alpha.-neuraminic acid, N-acetyl-neuramin-lactose and fetuin. Activities of 14 other lysosomal enzymes were within the range of normal control fibroblasts. The sialidase activities in fibroblasts from the patient''s parents and children were 30-60% of normal. This is the 1st proven case of a new autosomal recessive disorder resulting in cherry-red spots, myoclonus and a sialidase deficiency.

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