There are several types of Niemann-Pick disease. Carrier screening is typically offered for Type A and Type B. Type A is more common in the Ashkenazi Jewish population than in other groups, whereas Type B is seen in both Ashkenazi and non-Ashkenazi people.

Niemann-Pick disease, Type A (NP-A) is a severe, progressive disease that causes an extremely large liver and spleen, significant developmental delay, feeding difficulties, gastrointestinal problems, frequent lung infections, and often respiratory failure. On eye exam, people with NP–A have an unusual appearance to the retina, known as a cherry-red spot. Children with Niemann-Pick, Type A often appear normal at birth and have a short period of typical development (a few months) before the onset of neurological deterioration. Death usually occurs within the first few years of life.

Niemann-Pick disease, Type B (NP-B) is milder and has a later age of onset than NP-A. People with NP-B have an enlarged liver and spleen, respiratory difficulties, and growth delay. They typically have little or no neurological involvement and can live into adulthood.

There is no cure for Niemann-Pick disease, Type A or Type B. Treatment consists of managing the symptoms.

Niemann-Pick disease, Types A and B are caused by the deficiency of an enzyme called acid sphingomyelinase. In people with NP-A, this enzyme is absent or nearly absent, whereas people with NP-B have about 5-10% of the normal amount of this enzyme, resulting in a milder disease course. The lack of this necessary enzyme causes a substance (sphingomyelin) to build up in the cells and tissues of the body, resulting in the symptoms of Niemann-Pick disease.

One in 90 people with Ashkenazi Jewish ancestry is a carrier of Niemann-Pick Type A or Niemann-Pick Type B.

How Is Niemann-Pick Disease Inherited?

The cells in our body typically contain 46 chromosomes. Each chromosome is a package that holds hundreds of genes. These genes contain the all of the blueprints for our growth and development; they are the instructions that make us who we are. All of our chromosomes (and the genes that are located on these chromosomes) come in pairs. We inherit one chromosome of each pair from our mother and the other chromosome of the pair from our father.

 
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When there is a change in a gene (called a mutation) the instructions it contains are no longer correct and the gene cannot carry out its function. People with Niemann-Pick disease have two copies of a mutation, one copy inherited from each parent. Neither gene in the pair is working correctly, which causes the symptoms of the disease.

A carrier of Niemann-Pick disease is a person who has a mutation in one gene of the pair. Carriers are unaffected with the disease because the properly working gene is able to compensate for the gene that contains the mutation.

When two parents are carriers of Niemann-Pick disease:

• there is a 1 in 4 (25%) chance of having a child with Niemann-Pick disease,
• there is a 1 in 2 (50%) chance of having a child who is an unaffected carrier like the parents,
• and, there is 1 in 4 (25%) chance of having a child who is unaffected and is not carrier.

When one parent is a carrier of Niemann-Pick disease and the other parent is not, they are not at increased risk to have a child with Niemann-Pick disease. Instead, there is a 1 in 2 (50%) chance of having a child with is an unaffected carrier like the one parent.

What This Test Tells You

This test tells whether you are a carrier of Niemann-Pick disease. It looks for the four mutations that account for 95% of the cases of Niemann-Pick disease (Types A and B) in people of Ashkenazi Jewish descent. These mutations are called: R496L, L302P, fsP330 (TypeA) and deHaR608 (Type B) in the SMPD1 gene.

How Testing Works

Testing with DNA Direct is quick, convenient, and can be done in the privacy of your home. It can also be anonymous if you wish. How to order online and consult with our genetic experts: DNA Direct's Expert Services