A case of G M2 gangliosidosis of late onset.

A case of G(M2)-gangliosidosis commencing by the age of 5 years is described, in which hyperacusis, dementia, and fits were prominent clinical features. In addition to the typical ganglioside pattern on thin layer chromatography and the presence of membranous bodies in electron microscopic studies and characteristic histology and histochemistry, there was biochemical evidence of a gross reduction in heat-labile hexosaminidase activity in white blood cells and brain. A younger unaffected sibling showed the same enzyme defect in white blood cells.