Both the A and B types of this disease are due to primary deficiency of acid sphingomyelinase. In type A there is early hepatosplenomegaly and a progressive psychomotor deterioration with death by age 3 years. About half the patients have a macular cherry-red spot. There is an increased incidence of the disease in Ashkenazi Jews. In type B the main problems are visceral with early splenomegaly, later hepatomegaly and infiltration of the lungs. The disease is usually non-neuropathic but neurological signs may appear in later life.
ENZYME TESTS: Deficiency of sphingomyelinase is the primary defect.