Definition:

Defects in the degradation of sphingomyelin are a group of autosomal recessive lysosomal storage diseases including Niemann-Pick disease (NPD), type A/B and Farber lipogranulomatosis. NPD is caused by deficient acid sphingomyelinase (ASM) activity, and Farber lipogranulomatosis is caused by acid ceramidase deficiency, resulting in accumulation of sphingomyelin, ceramide and cholesterol in many organs. ASM and acid ceramidase are key enzymes of the two steps degradation of sphingomyelin and play important roles in normal membrane turnover.