 Niemann-Pick disease NPD is a group of rare inherited disorders of fat metabolism. At least five types of Niemann-Pick disease have been identified NPD types A, B, C, D, and E. Symptoms of types A and B occur as a result of a deficiency of the enzyme acid sphingomyelinase ASM, which is needed to break down sphingomyelin, a fatty substance found mostly in the brain and nervous system. This deficiency results in abnormal accumulation of excessive amounts of sphingomyelin in many organs of the body such as the liver, spleen, and brain. Symptoms of type C occur because of impaired trafficking of large molecules within cells, which results in the accumulation of excessive amounts of cholesterol and glycosphingolipids tissues throughout the body. The metabolic defect in type C can lead to a secondary reduction in ASM activity in some cells. Symptoms common to all types of Niemann-Pick disease include yellow discoloration of the skin, eyes, andor mucous membranes jaundice, progressive loss of motor skills, feeding difficulties, learning disabilities, and hepatosplenomegaly. The different types of Niemann-Pick disease are inherited as autosomal recessive traits. 