Inherited Diseases
Advances in genetic technology have focused new attention on screening for inherited conditions, as well as for sporadic disorders such as Down’s syndrome. There are thousands of inherited diseases, most of them rare. Here are examples of diseases for which many people are now screened:
* CONGENITAL HYPOTHYROIDISM: Results when the thyroid gland fails to develop properly. Newborns in all states are screened. Cases are sporadic. Occurs in about one in 4,000 white infants and one in 30,000 black infants. Can cause mental and physical retardation. Prompt treatment with thyroid hormone is very effective.
* NEURAL TUBE DEFECTS: Birth defects of the spinal column that can cause varying degrees of paralysis or, in extreme cases, absence of the brain. Prenatal diagnosis is usually recommended; California has a state sponsored screening program for pregnant women. Clusters in families but most cases are sporadic. Occurs in about nine in 10,000 births. Recent data suggests that folic acid supplements prior to conception and during early pregnancy can prevent recurrence in many cases.
* PHENYLKETONURIA: Results from a genetic defect in the metabolism of phenylalanine, an amino acid. Can cause mental retardation. Newborns in all states are screened. Occurs in about one in 14,000 births. A phenylalanine restricted diet is usually an effective treatment.
These are examples of diseases for which preconception or prenatal screening of at-risk families is often advised.
* DOWN’S SYNDROME: Birth defect characterized by mental retardation and physical abnormalities. Prenatal testing, such as amniocentesis, usually recommended for at-risk women. Occurs in one in 600 to one in 650 births; most frequent in infants of women over 35 years of age. Researchers are developing blood tests that can also be used in diagnosis.
* SICKLE CELL ANEMIA: A blood disease that occurs almost exclusively in blacks. Affected individuals have episodes of severe pain and are at increased risk for serious infections. With improved treatments, more patients are surviving to age 50 or beyond. In the United States, there are about 60,000 people with sickle cell anemia.
* TAY-SACHS DISEASE: Uncommon nervous system ailment that is usually fatal by 4 years of age. Most common in families of Eastern European Jewish origin. There is no specific treatment.
