Niemann-Pick type A is a very serious disease and type B is a subtype of mild Niemann-Pick disease. It is an autosomal recessive lysosomal disorder characterized clinically by its appearance in the neonatal period or in early childhood that causes developmental delay, hepatosplenomegaly, and rapidly progressing neurodegenerative disorders.
Niemann-Pick type A is due to an absence of the enzyme acid sphingomyelinase (ASM), whose function is to help metabolize sphingomyelin found in every cell of the body. If this enzyme is missing or does not function properly, destruction of cells occurs and difficult the proper functioning of some organs.
Type A occurs in all races and ethnic groups, being more common in the Ashkenazi Jew population (Eastern Europe).