Definition:
Niemann-Pick Type B is caused by the deficiency of the enzyme, acid sphingomyelinase (ASM) required to metabolize a lipid called sphingomyelin. If ASM is absent or functioning improperly, sphingomyelin cannot be broken down effectively and instead builds up within the cell. This accumulation eventually causes cell death and the major organ systems to fail. Those individuals affected with Niemann-Pick Type B have approximately 10% of the normal level of ASM in their bodies.

There are three separate forms of Niemann-Pick disease. Types A and Type B are genetically related and are disorders of lipid metabolism. The third type, Type C, is a disorder of lipid transport. Athough all races and ethnicities are affected by Niemann-Pick Type B, there is a higher incidence of the acute infantile form of this disorder within the Ashkenazi Jewish population. It is estimated that one in 1000 Ashkenazi Jews is a carrier for either Niemann-Pick Disease Type A or Type B.  Worldwide, cases of Niemann-Pick Type A and B together total approximately 1,200, but the incidence of Type B as an individual disorder is unknown.

Symptoms:
The symptoms of Niemann-Pick Type B manifest during pre-teen years. Symptoms include an enlarged liver and spleen.  The affected child experiences progressive organ enlargement, poor growth and susceptibility to respiratory infections ,but rarely displays neurological problems.

Inheritance Pattern:
Niemann-Pick Type B is an autosomal recessive disorder.

Life Expectancy:
Individuals with Niemann-Pick Type B typically live into adulthood.

Diagnosis and Testing:
Patients with Niemann-Pick Type B typically have less than 10 percent of normal activity of ASM but more than 3 to 5 percent activity. Prenatal diagnosis is possible by measuring enzyme activity or by identifying mutations in the ASM gene.

Treatment:
Bone marrow transplantation has been met with some success in patients with Niemann-Pick Type B. Some affected individuals may require supplemental oxygen because of decreased lung function. Enzyme replacement therapy is currently under investigation.

Patient Groups:
National Niemann-Pick Disease Foundation
P.O. Box 49
401 Madison Ave. Ste B
Fort Atkinson, WI 53538
www.nnpdf.org
tel: (920) 563-0930
fax: (920) 563-0931
Nadine Hill, Director of Family Services
nnpdf@nnpdf.org

National Tay-Sachs & Allied Diseases Association
2001 Beacon Street, Suite 204
Boston, MA 02135
www.ntsad.org
tel: (800) 906-8723
fax: (617) 277-0134
Sue R. Kahn, Executive Director
info@ntsad.org