Niemann-Pick Disease Type A and Type B
What is Niemann-Pick disease type A and type B?
Niemann-Pick disease, also called acid sphingomyelinase deficiency, is caused by the body not having enough of a specific enzyme called sphingomyelinase. Without normal levels of this enzyme in the body, certain fats build up and cause damage to organs such as the spleen and liver. There are three forms of Niemann-Pick disease - type A, type B and type C. Types A and B are screened for on the Eli test.
Babies with Niemann-Pick type A usually start to show symptoms by the time they are 3 months old. The first symptom is often an enlarged spleen. They may also show a “cherry red spot” in the eyes and have slowed physical and mental development after the first year.
People with Niemann-Pick type B begin to show symptoms later, usually during mid-childhood. The signs and symptoms of type B are similar to type A, although most are less severe. Niemann-Pick type B may also cause lung problems.
How common are Niemann-Pick disease type A and type B?
About 1 in 45,000 babies are born with Niemann-Pick types A and B disease each year in the United States.
What can be done for Niemann-Pick disease type A or type B?
Identifying the condition early (soon after birth) may lead to reduced symptoms and an improved quality of life. Certain symptoms can be treated with physical and occupational therapies. Also, a promising form of treatment that replaces the missing enzyme in the body is under investigation as part of clinical trials.
How are Niemann-Pick disease type A and type B inherited?
Niemann-Pick disease type A and type B are caused by changes in the SMPD1 gene. They are recessive inherited conditions, which means that a person must inherit two altered copies of the SMPD1 gene, one from each parent, in order to have the disease. People who have only one copy of the altered SMPD1 gene are called carriers, and are not expected to have symptoms of the condition. If a baby is identified as a carrier for Niemann-Pick disease type A or type B through Eli screening, genetic counseling and additional testing in the parents is recommended.
Acuña M, Martínez P, Moraga C, He X, Moraga M, Hunter B, Nuernberg P, Gutiérrez RA, González M, Schuchman EH, Luis Santos J, Miquel JF, Mabe P, Zanlungo S. Epidemiological, clinical and biochemical characterization of the p.(Ala359Asp) SMPD1 variant causing Niemann-Pick disease type B. Eur J Hum Genet. 2016;24:208–13.