Niemann-Pick disease is a rare inherited degenerative nerve disease caused by the deficiency of the enzyme called sphingomyelinase, which leads to the buildup of a fatty substance (sphingomyelin) in cells in the liver, spleen, lymph nodes, and bone marrow. Niemann-Pick disease is most commonly seen in families of Eastern European (Ashkenazi) Jewish heritage.

At least five types of Niemann-Pick disease have been identified. The most common are type A and type B.

• Type A usually causes symptoms by 6 months of age. Symptoms may include feeding difficulty, vomiting, and abdominal distention from an enlarged spleen and liver. Some babies have a cherry-red spot in the membrane that lines the back of the eye (retina). Infections such as pneumonia are common. Death usually occurs by the age of 4.
• Type B disease is a milder form that does not affect the brain. Children are usually diagnosed during early childhood because of enlargement of the liver or spleen. Teenagers with type B disease may have frequent lung infections. Most people with type B Niemann-Pick disease live into their 30s or 40s.
• Type C usually shows up during childhood. It can cause breathing problems, liver disease, developmental delays, seizures, low muscle tone, and feeding problems. It is the rarest type of Niemann-Pick disease. Most people with type C die by the age of 20. The kind of genetic change (mutation) determines whether a person has type C1 or C2.

There is no treatment for Niemann-Pick disease. Support groups and counseling can be helpful for people with Niemann-Pick disease and for their families. Genetic testing is recommended to identify carriers of the disease and help guide decisions about having children.