Niemann-Pick disease (NP) refers to a group of inherited metabolic disorders known as the leukodystrophies or lipid storage diseases in which harmful quantities of a fatty substance (lipids) accumulate in the spleen, liver, lungs, bone marrow, and the brain. Symptoms may include lack of muscle coordination, brain degeneration, learning problems, loss of muscle tone, increased sensitivity to touch, spasticity, feeding and swallowing difficulties, slurred speech, and an enlarged liver and spleen. There may be clouding of the cornea and a characteristic cherry-red halo develops around the center of the retina. The disease has 4 related types. Type A, the most common type, occurs in infants. It is characterized by jaundice, an enlarged liver, and profound brain damage. Children with this type rarely live beyond 18 months. Type B involves an enlarged liver and spleen, which usually occurs in the pre-teen years. The brain is not affected. In types A and B , insufficient activity of an enzyme called sphingomyelinase causes the build up of toxic amounts of sphingomyelin , a fatty substance present in every cell of the body. Types C and D may appear early in life or develop in the teen or adult years. Affected individuals have only moderate enlargement of the spleen and liver, but brain damage may be extensive and cause an inability to look up and down, difficulty in walking and swallowing, and progressive loss of vision and hearing. Types C and D are characterized by a defect that disrupts the transport of cholesterol between brain cells. Type D usually occurs in people with an ancestral background in Nova Scotia.
There is currently no effective treatment for persons with type A . Bone marrow transplantation has been attempted in a few patients with type B , and encouraging results have been reported. The development of enzyme replacement and gene therapies might also be helpful for those with type B . Individuals with types C and D are frequently placed on a low-cholesterol diet, but its clinical benefit is not convincing.
Infants with type A die in infancy. Children with Type B may live a comparatively long time, but may require supplemental oxygen because of lung impairment. The life expectancy of persons with types C and D varies: Some individuals die in childhood while others, who appear to be less severely affected, live into adulthood.
Prepared by the National Institutes of Health