Niemann-Pick disease is a lysosomal storage disease also known as sphingomyelinosis. It is an autosomal recessive hereditary disease due to lack of the enzyme sphingomyelinase, which results in the accumulation of sphingomyelin within cells of the nervous system and organs such as liver, spleen, kidneys, lung and intestines.
Clinical signs are apparent from 3 months of age and include ataxia (uncoordinated walking), hypermetria (high stepping walk), head tremors, loss of balance and splayed legs. Some cats show stereotypic chewing, and the liver and spleen may be palpably enlarged. Progressive paralysis develops, with most cats dying before 1 year of age. Diagnosis relies on demonstrating the enzyme deficiency in tissues such as liver, brain or skin fibroblasts. Variant forms of the disease have been described (Niemann-Pick A and Niemann-Pick C). The defective gene for Niemann-Pick C (NPC1) has been identified in cats.
Niemann-Pick disease has been described in Siamese and domestic shorthair cats.