A female infant with early-onset GM1-gangliosidosis type I was investigated. The 
lymphocytes, transformed lymphocytes and cultured skin fibroblasts of the 
patient were demonstrated to have severe beta-D-galactosidase deficiency. The 
beta-D-galactosidase activities of these cells from the patient's father and 
mother were at the lower limit of the normal range. The oligosaccharide 
accumulation in urine of the patient showed the typical type I 
GM1-gangliosidosis pattern, but no GM1 ganglioside was detected in the patient's 
urine or transformed lymphocytes. The clinical features were compatible with 
infantile GM1-gangliosidosis. The mixture of homogenates from the cultured 
fibroblasts or transformed lymphocytes of the patient and controls showed no 
complementation of beta-D-galactosidase activity against the controls.