Fragile X Syndrome
- mental impairment, ranging from learning disabilities to mental retardation
- attention deficit and hyperactivity
- anxiety and unstable mood
- autistic behaviors
- long face, large ears, flat feet
- hyperextensible joints, especially fingers
- Seizures (epilepsy) affect about 25% of people with fragile X
Boys are typically more severely affected than girls. While most boys have mental retardation, only one-third to one-half of girls have significant intellectual impairment; the rest have either normal IQ or learning disabilities. Math is often a particular challenge for girls. Emotional and behavioral problems are common in both sexes. About 20% of boys with fragile X meet full criteria for autism. Most boys and some girls have some symptoms of autism, but many tend to be very social and interested in other people.
Fragile X is caused by a single gene. Drs. Ben Oostra, Stephen Warren, and David Nelson discovered the gene for Fragile X.Some individuals are carriers. They have a small defect in a particular gene but do not show symptoms. Fragile X is inherited. Carrier men pass the premutation to all their daughters but none of their sons. Each child of a carrier woman has a 50% chance of inheriting the gene defect. The Fragile X permutation can be passed silently down through generations in a family before a child is affected by the syndrome. Fragile X syndrome is the most common inherited cause of mental impairment and the most common known cause of autism. Fragile X affects 1 in 4000 males and 1 in 6000 females of all races and ethnic groups (source Centers for Disease Control). About 1 in 259 women carry fragile X and could pass it to their children. About 1 in 800 men carry fragile X; their daughters will also be carriers.
A DNA test for Fragile X was developed in 1992. This blood test is accurate and can detect both carriers and fully-affected individuals. It can be ordered by any physician; the blood sample is then sent to a lab that offers the test. It usually takes several weeks to get the results. Because the symptoms of Fragile X can be subtle, especially in young children, and because it is so frequent in the general population (1 in 4000 males and 1 in 6000 females), Fragile X testing should be considered for any individual with otherwise unexplained developmental delay or mental retardation.
There is currently no cure for Fragile X, although appropriate education and medications can help maximize the potential of each child. However, most boys and many girls remain significantly affected throughout their lives. The cost to society for treatment, special education, and lost income is staggering. The need for research aimed at treatment is urgent.