Three sisters with infantile-onset 3 GM1 gangliosidosis are reported from the University of Siens, Italy, and the University of Louvain, Brussels, Belgium. The diagnosis was based on the clinical findings of progressive intellectual deterioration by age 6-8 years, ataxia, spastic tetraparesis, and athetoid-choreiform movements; lysosomal vacuoles in CSF, bone marrow, and conjunctiva; and on decreased activity of serum, leukocyte, and fibroblast B-D-galactosidase and abnormal urinary excretion of oligosaccharides. 
COMMENT. Gangliosidosis occurs in 3 forms: 1) infantile, characterized by Hurler's facial features, bony abnormalities, hepatoslenomegaly, cherry-red spot, and progressive neurological signs; 2) late infantile-juvenile, without skeletal changes or marked visceromegaly, but severe intellectual deterioration, ataxia, myoclonic seizures, and retinal degeneration; and 3) dystonic juvenile form. The clinical findings in the present report resembled those in the dystonic form except that the intellectual deterioration was more severe.