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Niemann-Pick disease is an autosomal recessive lysosomal storage disorder caused by the deficient activity of acid sphingomyelinase. Failure to hydrolyze sphingomyelin to ceramide causes intracellular accumulation of sphingomyelin. Clinical aspects have led physicians to distinguish two forms of Niemann-Pick disease: type A and type B. Type A (frequency in France is approximately 1/500,000) is characterized by an early onset, within the first year of life, digestive disorders, failure to thrive, major hepatosplenomegaly, and severe neurologic symptoms (psychomotor retardation, hypotonia). The severe neurological disorders and pulmonary infections lead to an early death, often around the age of 4. In type B (frequency in France is about 1/200,000), onset occurs at any age (until adulthood) and the most constant sign is hepatosplenomegaly, which can be associated with pulmonary symptoms. Diagnosis is confirmed by assaying the activity of acid sphingomyelinase. Prenatal diagnosis is available. As of today, there is no specific therapy; only symptomatic treatment can be offered.
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