Retrospective Diagnosis of GM1 Gangliosidosis by Use of a Newborn- Screening Card To the Editor:

A deficiency of lysosomal b-d-galac-tosidase (bG; EC 3.2.1.23) is the pri-mary defect in the three clinical forms (infantile, juvenile, and adult) of GM1 gangliosidosis and in Morquio B syndrome. Patients with the infantile form of GM1 gangli-osidosis (type 1), who usually die before the age of 3 years, display the coarse face, hepatosplenomegaly, and skeletal dysplasia reminiscent of Hurler disease. Cases with later on-set, described as the late infantile/ juvenile form (type 2), display pro-gressive psychomotor loss but les