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Niemann-Pick
Disease
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Description
Niemann-Pick is an autosomal recessive genetic disease.
There are four clinical types of Niemann-Pick Disease, all
inherited.
Type A and Type B are caused by the lack of a substance called ASM-acid
sphingomylinase which breaks down a substance called sphingomyeline.
Lack of ASM causes buildup of sphingomyeline in certain cells and
causes damage to the central nervous system, liver, and lungs.
Though both Type A and B are caused by deficiency of ASM, Type A,
which is most prevalent, is a severe neurological disease that
generally leads to death between two and three years of age. Type B
has little or no neurological involvement and many survive into late
childhood or adulthood.
Type C and D are also caused by excess deposition of sphingomyelin,
as patients do not properly transport sphingomyelin and that too
results in its accumulation of sphingomyeline. However, it is the A
and B types of Niemann-Pick Disease that have a higher incidence in
Ashkenazi Jews, compared to the general population.
Symptoms
Symptoms of Neimann-Pick Type A
The prognosis of Type A is dismal, and usually a baby with this form of
Niemann-Pick Disease succumbs by the second year of life. Symptoms and signs of
Type A include:
· Abdominal distention
· Coordination and motor-skill
difficulties
· Feeding problems
· Progressive spasticity
· Blindness
· Enlarged liver, and\or spleen
· A “ cherry red spot” in the eye,
visible by special eye exam.
· May also present with jaundice in
infancy and progressive liver failure.
Symptoms of Niemann-Pick Type B
Neimann-Pick Type B is less extreme and does not affect the brain. However, it
does cause liver, spleen, lymph node, and bone marrow problems and generally
leads to abdominal distention and respiratory difficulties.
Treatment
Currently Mount Sinai Hospital in New York in conjunction with Genzyme
Corporation is working on new treatment modes for Type B Niemann-Pick Disease.
They will be focusing on Enzyme Replacement Therapy and Gene Therapy.
Incidence
and Carriers
Disease Frequency: 1 in 40,000 for type A in the Jewish population
Carrier Frequency: One in 90 Ashkenazi Jews is a Type A carrier. Unknown
for type B though it is estimated to not be greater than any other race.
The disease is transmitted through heredity. Both parents have to carry the
Niemann-Pick gene for there to be a possibility of transmission to their child.
If both parents are carriers then:
· There is a one in four chance that the
child will inherit the Niemann-Pick gene from each parent and have the disease
· There is a one in four chance that the
child will inherit normal genes from both parents and be completely free of the
disease.
· There is a two in four chance the
child will inherit one of each kind of gene and be a carrier like the parents,
and free of the disease.
· Unaffected siblings have a two in
three chance of being carriers.
Testing
Diagnosis
Diagnosis is achieved by testing blood, and measuring the ASM activity in the
white blood cells. This
test
is effective in identifying persons actually victims of Type A and B but is
not reliable in detecting persons who are carriers of Niemann-Pick.
There is a carrier screening
test
which requires a sample of blood that can determine whether or not a
gene change is present in the gene for Neiman-Pick.
There is a carrier
screening test which requires a sample of blood that can determine
whether or not a gene change is present in the gene for
Neiman-Pick.
Prenatal diagnosis for Niemann-Pick can be attained with the use of
CVS (Chorionic Villus Sampling) or Amniocentesis, which are
performed early in the pregnancy.
Resources and More
National Neiman-Pick Disease Foundation, Inc.
3734 East Olive Avenue
Gilbert, AZ 85234
Telephone: 602-497-6638
Website:
For Genetic
Counseling and Screening Resources – Click Here
Support Group
National Neiman-Pick Disease Foundation, Inc.
3734 East Olive Avenue
Gilbert, AZ 85234
Telephone: 602-497-6638
Website:http://www.nnpdf.org
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