Report of an infant with GM1 gangliosidosis type I and extensive and unusual mongolian spots.

An infant with GM1 gangliosidosis was found to have an eruption at birth consisting of extensive and unusual slate blue macules resembling mongolian spots. All areas of skin were involved except face, scalp, palms, and soles. A biopsy of a macule obtained at 5 months of age demonstrated melanocytic cells in the dermis consistent with monogolian spot but also a perivascular histiocytic infiltrate. At 8 months of age, absence of beta-galactosidase activity was documented in both peripheral leukocytes and skin fibroblasts confirming the diagnosis of GM1 gangliosidosis. The dermal histiocytic cells noted on skin biopsy were interpreted as a manifestation of this storage disease. The coexistence of the hyperpigmented lesions and the heritable enzyme defect was believed to be coincidental.