We report a case of a 36-year-old woman with progressive generalized myoclonus that first became apparent 9 years ago. Her younger brother had similar problems. Examination of her eyes revealed cherry-red spots. Hexosaminidase A, β-galactosidase and neuraminidase activity were normal. Although the laboratory findings were negative, cherry-red spots, progressive myoclonus and autosomal recessive inheritance pattern suggested that she had an unknown type of lysosomal storage disease.