This gene carries instructions for cells to produce a lysosomal enzyme called acid sphingomyelinase.
Insufficient activity of the enzyme acid sphingomyelinase causes the buildup of toxic amounts of sphingomyelin, a fatty substance present in every cell of the body.
[citation needed] Niemann–Pick type A, the most common type, occurs in infants and is characterized by jaundice, an enlarged liver, failure to thrive, progressive deterioration of the nervous system and profound brain damage.
Niemann–Pick Type A occurs more frequently among individuals of Ashkenazi (eastern and central European) Jewish descent than in other ethnicities.
[citation needed] Niemann–Pick type B presents similarly to Gaucher's disease and involves an enlarged liver and spleen (hepatosplenomegaly), growth retardation, and problems with lung function including frequent lung infections.