Niemann-Pick disease refers to a group of inherited conditions that affect the body’s metabolism. In patients with this rare disorder, fatty material builds up in various vital organs, sometimes including the brain.

There are four main types of Niemann-Pick disease:

  • Type A—causes fatty substances to collect in the liver and spleen. Patients have severe brain damage and usually die by age two or three.
  • Type B—affects the liver and spleen. Organs enlarge during the pre-teen years. There is usually no brain damage. Patients usually suffer from breathing problems and die in teen years or early adulthood. The prognosis is better for type B than type A.
  • Type C—produces extensive brain damage. The liver and spleen are moderately enlarged. Type C usually starts in childhood and leads to death in teen years or early adulthood.
  • Type D—similar to type C, but occurs only in people related to a family that lived in Nova Scotia at the start of the 1700s. Type D is now recognized as a variation of type C.

Liver and Spleen
Child intestines
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Niemann-Pick disease is inherited. It is an autosomal recessive trait, which means that both parents must carry the abnormal gene for their child to inherit the disease. The exact cause depends on the type of Niemann-Pick disease.

Types A and B

A fatty material called sphingomyelin builds up in the patient's organs. This substance is normally present in the membrane of most cells. The enzyme sphingomyelinase normally breaks down this substance. However, people with type A or B either do not have enough of this enzyme or this enzyme does not work properly. Without the properly functioning enzyme, this fatty material builds up in the cells. The cells die and the organ does not work properly.

Types C and D

In these two types, nerve cells in the brain are unable to move cholesterol out. This allows cholesterol to build up, which keeps cells from functioning normally.