Fragile X syndrome

Fragile X syndrome is a genetic abnormality in an X chromosome that leads to delayed development and other symptoms.
The symptoms of fragile X syndrome are caused by abnormalities in DNA on the X chromosome. Usually, affected boys inherit the condition from their mothers.

Many children with the syndrome have normal intelligence. However, the syndrome is the most commonly diagnosed genetic cause of mental retardation besides Down syndrome. The severity of symptoms, including mental retardation, is worse in boys than in girls with the disorder. Symptoms, which are often subtle, include delayed development; large, protuberant ears; a prominent chin and forehead; and, in boys, large testes (most apparent after puberty). The joints may be abnormally flexible, and heart disease (mitral valve prolapse) may occur. Features of autism may develop. Women may experience menopause in their mid 30s.

The presence of abnormal DNA on the fragile X chromosome can be detected by tests before or after birth. The greater the number of abnormal repetitions of DNA found, the more likely the child will have symptoms.

Early intervention, including speech and language therapy and occupational therapy, can help children with fragile X syndrome to maximize their abilities. Stimulants, antidepressants, and antianxiety drugs may be beneficial for some children.