Genetic Disorder Profiles and Organizations
Adenosine Deaminase Deficiency (ADA)
Affects: 1 out of 100,000
Type of trait: autosomal recessive
Chromosome on which gene is located: 20
Test applications: prenatal, carrier
Children with this disease have a defective immune system, and are susceptible
to all types of infections. Gene therapy
is being tested as a potential cure.
Cystic Fibrosis
Affects: 1 out of 2,500 Caucasians; 1 out of 90,000
African Americans
Type of trait: autosomal recessive
Chromosome on which gene is located: 7
Test applications: carrier, prenatal, newborn
Cystic fibrosis results in the secretion of a thick mucous in the lungs
that blocks the flow of air. The disorder also causes digestive problems,
salty-tasting skin, and susceptibility to respiratory tract infections.
Cystic fibrosis is progressive and requires extensive medical treatment
with antibiotics and digestive enzymes.
It also requires daily respiratory therapy. Left untreated, most children
will die by the time they are four or five. A special diet, daily doses
of antibiotics to prevent infection, and other treatments can extend life
expectancy to adolescence or later. About 40% of people with cystic fibrosis
live to the age of 30.
Resource Organization:
National Cystic Fibrosis Foundation
6931 Arlington Road
Bethesda, MD 20814
800/344-4823 or 301/951-4422
Diabetes Mellitus Type I
Affects: 1 out of 300
Type of trait: polygenic
Chromosome on which gene is located: 6 and others
Test applications: presymptomatic
Type I diabetes mellitus results from destruction of the cells in the
pancreas that make the hormone insulin. The loss of the insulin causes uncontrolled
breakdown of tissues and elevated blood sugar levels, progressing rapidly
to death unless treated with insulin. Lifelong treatment with insulin is
necessary. Because more than one gene along with environmental factors contributes
to development of the disease, only 3-6% of children of parents with type
I diabetes develop the disease.
Resource Organization:
National Diabetes
Information Clearinghouse
1 Information Way
Bethesda, MD 20892-3560
301/654-3327
Down Syndrome (Trisomy 21)
Affects: 1 out of 800
Type of trait: extra chromosome (trisomy)
Chromosome on which gene is located: extra 21
Test applications: prenatal
People with Down syndrome have distinctive features, including a depressed
nose bridge, a round face, and up-slanted eyes. There is also some degree
of mental retardation. Early deaths in Down syndrome are sometimes due to
leukemia, infection, or heart disease. Lifetime care is usually required.
Resource Organizations:
Association for Children with Down Syndrome
2616 Martin Avenue
Bellmore, NY 11710
516-221-4700
National Down Syndrome Society
666 Broadway Avenue
New York, NY 10012
800-221-4602
Duchenne Muscular Dystrophy
Affects: 1 out of 4,000 males
Type of trait: X-linked recessive
Chromosome on which gene is located: X
Test applications: carrier, prenatal, confirmatory
This disease predominately affects males. Symptoms, which include weakening
of the leg and pelvic muscles, first appear around the age of 3 or 4. The
muscles continue to degenerate over time. Death, usually due to respiratory
failure, often occurs in the twenties and thirties.
Resource Organization:
Muscular Dystrophy Association
3300 East Sunrise Drive
Tuscon, AZ 85718
520/529-2000
Familial Alzheimer Disease
Affects: 1 out of 2-4 million adults
Type of trait: autosomal dominant
chromosomes on which gene is
located: 1, 14, 21
Test applications: presymptomatic, confirmatory
Symptoms of this disease begin to appear when a person is in his or her
late 30s to 40s. They include loss of memory, intellectual deterioration,
disorientation, apathy, and abnormal speech and movements. No cure exists.
Resource Organization:
Alzheimer's Disease and Related Disorders
Association
919 N. Michigan Avenue, Suite 1000
Chicago, IL 60611
800-272-3900 or 312/335-8700
Fragile X
Affects: 1 out of 2,000 males; 1 out of 3,000 females
Type of trait: X-linked recessive
Chromosome on which gene is located: X
Test applications: carrier, prenatal, confirmatory
Fragile X Syndrome is the most common inherited cause of mental retardation.
Other symptoms include learning disabilities, speech and language problems,
and a loose-jointed walk. There is currently no cure for the disease.
Resource Organization:
National Fragile X Foundation
1441 York
Denver, CO 80206
800-688-8765 or 303/333-6155
Familial Hypercholesterolemia
Affects: 1 out of 500 (heterozygous);
1 out of 1 million (homozygous)
Type of trait: autosomal semidominant
Chromosome on which gene is located: 19
Test applications: newborn, confirmatory
People with familial hypercholesterolemia have high levels of cholesterol
in their blood from birth. The cholesterol can gradually build up in artery
walls, causing narrowing of the arteries. This process is known as atherosclerosis.
Without treatment, a heart attack can result as early as age 25, although
the average is in the forties for men and fifties for women. Usually no
other symptoms are present, but some affected people develop cholesterol
deposits in their tendons, which can become painful. With the proper combination
of cholesterol-lowering medication, diet, exercise, and avoidance of cigarette
smoke, most people with familial hypercholesterolemia can live normal lives
and may never have a heart attack.
Galactosemia
Affects: 1 out of 80,000
Type of trait: autosomal recessive
Chromosome on which gene is located: 9
Test applications: carrier, prenatal, newborn
A person with galactosemia is intolerant to galactose, which is primarily
found in milk and milk products. If left untreated, disease can cause liver
failure, infection, cataracts, and mental retardation. No cure is available,
but early treatment and life-long dietary restrictions prevent serious symptoms.
Hemophilia A
Affects: 1 out of 20,000 males, some carrier females
Type of trait: X-linked recessive
Chromosome on which gene is located: X
Test applications: carrier, prenatal, confirmatory
A person with this disorder is unable to produce the clotting material
needed to stop bleeding. The person bleeds easily and may bleed to death
even from small cuts. There is currently no cure, but symptoms of hemophilia
can be treated effectively with a supplemental clotting factor to slow down
excessive bleeding.
Resource Organization:
National Hemophilia Foundation
110 Greene Street, Suite 303
New York, NY 10012
800/424-2634 or 212/219-8180
Huntington Disease
Affects: 1 out of 20,000 adults
Type of trait: autosomal dominant
Chromosome on which gene is located: 4
Test applications: prenatal, presymptomatic, confirmatory
This disorder of the central nervous system may first appear in adults
between the ages of 20 and 70, but most frequently appears in the forties
and fifties. A person with Huntington disease has involuntary jerky or writhing
movements. Other changes include dementia, personality changes, depression,
anger, and memory loss. In the final stages, the person usually enters an
almost vegetative state. The disease is fatal and currently uncurable.
Resource Organization:
Huntington Disease Society
of America
140 West 22nd Street, 6th Floor
New York, NY 10011-2420
800/345-4372 or 212/242-1968
Phenylketonuria (PKU)
Affects: 1 out of 10,000
Type of trait: autosomal recessive
Chromosome on which gene is located: 12
Test applications: carrier, prenatal, newborn
People with PKU cannot completely metabolize foods that contain the amino acid phenylalanine. Over time, the
partially metabolized phenylalanine builds up in the blood and damages brain
cells. Without early detection and treatment, individuals with PKU generally
suffer from severe mental retardation as well as behavior disorders, seizures,
and decreased pigmentation. There is currently no cure, but lifelong dietary
precautions can prevent mental retardation and other symptoms.
Resource Organization:
Children's PKU
Network
1520 State Street, Suite 240
San Diego, CA 92101
619/233-3202
Sickle-cell anemia
Affects: 1 out of 500 African Americans
Type of trait: autosomal recessive
Chromosome on which gene is located: 11
Test applications: carrier, newborn, prenatal
Sickle-cell anemia is a serious disorder in which the red blood cells
lose their round, slightly disk shaped appearance and collapse into sickle
shapes which cannot carry oxygen to the body cells. The flattened cells
also tend to block and clog capillaries, causing reduced circulation and
severe pain. People who have the disease may have shortened life expectancies.
Resource Organization:
Sickle-Cell Disease
Association of America, Inc.
200 Corporate Pointe, Suite 495
Culver City, CA 90230-7633
800-421-8453 or 310/216-6363
Tay-Sachs Disease
Affects: 1 out of 3,600 Ashkenazi Jews
Type of trait: autosomal recessive
Chromosome on which gene is located: 15
Test applications: carrier, prenatal, confirmatory
The brain cells in people with Tay-Sachs are unable to metabolize a particular
type of lipid. As lipids accumulate in the brain, brain cells gradually
cease to function normally. This results in nervous system degeneration,
uncontrollable convulsions, and total loss of sensory input. Children with
Tay-Sachs usually die by the age of four.
Resource Organization:
National
Tay-Sachs and Allied Diseases Association
92 Washington Avenue
Cedarhurst, New York 11516
516-569-4300
Thalassemia
Affects: 1 out of 2,500 of Mediterranean and Chinese/
Southeast Asian ancestry
Type of trait: autosomal recessive
chromosomes on which gene is located: 11 & 16
Test applications: carrier, prenatal, confirmatory
Children with this disorder are born normal, but become anemic between
the ages of 3-18 months. The children become pale, do not sleep well, have
decreased appetite, and fail to thrive. Current treatment includes frequent
blood transfusions. If not treated, children with this disorder may die
from anemia between the ages of 1 and 8.
Resource Organization:
Cooley's Anemia Foundation
129-09 26th Avenue, Suite 203
Flushing, New York 11354
800-522-7222 or 718/321-2873
General Genetic Disorder Resource Organizations
The following organizations provide a variety of services and activities,
including support groups, educational materials, and general information.
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
New York, New York 10605
914-428-7100
National Center for Human
Genome Research, Office of Communications
National Institutes of Health
Building 31, Room 4B09
31 Center Drive
Bethesda, MD 20892
301/402-0911
National Network to Prevent Birth Defects
701 E Street, S.E.
Washington, DC 20003
202-543-5450
For information on careers in genetic counseling:
National Society of Genetic Counselors, Inc.
233 Canterbury Drive
Wallingford, PA 19086
610/872-7608
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