Two adult patients with G(M1) ganglioside β-galactosidase deficiency, showing myoclonus without radiological bony abnormalities

Two adult patients aged 54 years and 27 years (mother and her second son) showed slowly progressive deterioration of central nervous system; myoclonus, dysarthria, pyramidal signs, ataxia, and intellectual impairment. Biochemical analyses on lymphocytes and cultured skin fibroblasts obtained from these patients revealed a profound deficiency in G(M1) ganglioside β-galactosidase. Activities of other lysosomal hydrolases including sialidase were found to be normal in lymphocytes and cultured skin fibroblasts. From the biochemical studies on other members of their family, we could detect the intermediate value of G(M1) ganglioside β-galactosidase activity in lymphocytes of two family members (grandmother and father of the son). These biochemical data were consistent with those in the adult form of G(M1) gangliosidosis reported previously. Although two patients showed various phenotypic varieties, such as onset of age (39 years and 25 years), convulsive seizure (mother), macular cherry red spots (son), they lacked radiological bony abnormalities and oligosacchariduria. These unique pictures and biochemical findings suggest the new phenotypic expressions in the patients with primary β-galactosidase deficiency, when compared with other cases described previously in the literature.