A new juvenile hexosaminidase deficiency disease presenting as cerebellar ataxia. Clinical and biochemical studies.

A boy with mild hand tremor since age 2 1/2 was found at 4 to have cherry-red spots and mild trucal ataxia without seizures or dementia. Biochemically, he had striking hexosaminidase deficiency (serum: 4.6 percent of normal, 88.9 percent heat-labile; leukocyte: 2.2 percent of normal, 84.6 percent heat-labile; fibroblast 12.8 percent normal, 93.1 percent heat-labile). The residual hexosaminidase activity migrated electrophoretically in two bands. The major band comigrated with hexosaminidase A, the minor with hexosaminidase S. Hexosaminidase B was totally absent. The parents had partially reduced hexosaminidase with a decreased heat-stabile fraction. This disorder may result from a new mutation closely related to that causing Sandhoff-Jatzkewitz disease.