Acid sphingomyelinase deficiency (ASMD)

Acid sphingomyelinase deficiency (ASMD) is a rare progressive genetic disorder that results from a deficiency of the enzyme acid sphingomyelinase, which is required to metabolize lipid called sphingomyelin. Consequently, sphingomyelin and other substances accumulate in various tissues of the body. ASMD is highly variable and the age of onset, specific symptoms and severity of the disorder can vary dramatically from one person to another, sometimes even among members of the same family. The disorder may be best thought of as a spectrum of disease. At the severe end of the spectrum is a fatal neurodegenerative disorder that presents in infancy (Niemann-Pick disease type A). At the mild end of the spectrum, affected individuals have no or only minimal neurological symptoms and survival into adulthood is common (Niemann-Pick disease type B). Intermediate forms of the disorder exist as well. ASMD is caused by mutations in the SMPD1 gene and is inherited in an autosomal recessive manner.