Five Genetic Tests to Determine Carrier Status for Diseases and Conditions
- Cystic Fibrosis
- Tay-Sachs and Ashkenazi Disorders
- Sickle Cell Anemia
- Spinal Muscular Atrophy (SMA)
Genetic Counseling is usually administered to couples thinking about becoming pregnant and want to know their risk for inherited diseases. One of the most popular forms is carrier testing, offered to individuals who are members of ethnic groups that have a concentration of certain genetic conditions or may have a family history of a disease. When prospective parents are tested, the information gained can indicate the likelihood of having a child with a specific condition. Genetic testing became popular with the testing of fetuses in utero to determine what conditions they may have.
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Testing for this disease is perhaps the most common as those afflicted with the disease rarely live beyond young adulthood. Even though it is a common genetic disease, most geneticists don’t recommend testing for this or other genetic diseases unless there is a predisposition in the family or some other pressing indication. The Cystic Fibrosis Foundation notes that more than 10 million Americans or one in every 31 people are symptomless carriers of the recessive cystic fibrosis transmembrane conductance regulator (CFTR) gene. Caucasian have a higher risk of carrying the CTFR gene mutation.
Tay-Sachs and Ashkenazi Disorders
A number of genetic diseases are common in individuals who have Jewish Ashkenazi ancestry. The same disorders are also common among French Canadians. Tay-Sachs is the most well-known of these diseases and involves the accumulation of lipids in the brain and spinal cord, destroying the nerve cells there and eventually leading to death. Other diseases on the Ashkenazi spectrum are not as severe.
The Genetic Support Foundation indicates that related disorders include:
- Familial Dysautonomia
- Canavan Disease
- Fanconi Anemia Group C
- Bloom Syndrome
- Nieman-Pick Type A
- Gaucher Disease
- Mucolipidosis IV
Sickle Cell Anemia
Sickle cell disease is a group of disorders that affects hemoglobin, which delivers oxygen to cells throughout the body. It is one of the most common hemoglobinopathies and is generally found among African American and Mediterranean populations. The condition is an autosomal recessive pattern, meaning that someone afflicted with sickle cell anemia has inherited mutations from both parents. Affecting as many as 80,000 people, it is the most common inherited blood disorder in the United States.
Another common hemoglobinopathy is thalassemia, most commonly found in people of Greek, Italian, Mediterranean or Southeast Asian descent. The most common forms are alpha-thalassemia and beta-thalassemia. About three percent of the world’s population carries the gene that causes this disease that results in the excessive destruction of red blood cells. Also called Cooley’s Anemia, beta-thalassemia is the more severe form of the disease and usually appears within the first two years of life.
Spinal Muscular Atrophy (SMA)
Spinal muscular atrophy (SMA) is a recessive disease that causes progressive muscle weakness and wasting. There are four different types, three of which are childhood onset. When the disease presents itself before 18 months of age, it is almost always fatal, even though some patients may live into adulthood. SMA is the leading genetic cause of death in infants. The carrier rate is one in 50 and it is present in about one of every 10,000 live births.
Genetic counseling primarily involves recessive diseases. A comprehensive screening for additional diseases is only given if there is a familial tendency for additional problems. Knowing the possibility that a genetic disease is possible can help parents make more informed decisions about having children or initiating early treatment for children who inherit a condition.