A 27-year-old woman was admitted for further examination of thrombocytopenia. Symptoms were absent, but physical examination demonstrated hepatosplenomegaly without neurological abnormalities. Bone marrow examination revealed many Gaucher cells, and glucocerebrosidase activity from cultured skin fibroblasts was markedly reduced. A 1448C (L444P) mutation was detected on one allele of the glucocerebrosidase gene. Because magnetic resonance imaging (MRI) of the femora indicated severe infiltration of Gaucher cells into bone marrow, enzyme replacement therapy was initiated despite the absence of skeletal symptoms. Hematologic abnormalities, visceral and bone involvement have been improving. In cases of thrombocytopenia or hepatosplenomegaly, Gaucher's disease should be suspected.