Fragile X Syndrome is an inherited genetic condition associated with mental retardation. It is caused by a mutation of the “X” chromosome. Fathers cannot pass the disease onto their sons, because females always give an “x” chromosome where a man gives either an “x” or a “y.” If a man gives a “y” chromosome, then the result is a boy baby, and since the disease is only carried in the “x” chromosome, a boy can only inherit this disease from his mother. A girl, on the other hand, can inherit the disease from either her father or mother. Interestingly enough, more boys than girls are affected by this disease.
Fragile X syndrome appears in children of all ethnic, racial, and economic backgrounds. It is second only to Down Syndrome as a chromosomal cause of mental retardation. It is suggested that testing be done on all people with mental retardation or autism where a cause is not known, people with extreme hyperactivity, learning disabilities, and/or mild cognitive deficits. Also, people with any of the physical or behavioral features of fragile X syndrome, regardless of sex or family history, are encouraged to be tested, as well as any member of a family exhibiting recurrent mental impairment. The greatest risk of producing a child with this disease would be if the mother and father are both affected or carriers. of the Fragile X chromosome.
The physical features of Fragile X include a long, narrow face, prominent jaw and forhead. Many children with Fragile X may not show all these features, but prominent ears are seen in approximately two-thirds of affected children. Loose joints are also quite common. In childhood, most Fragile X sufferers have hyperactivity symptoms, tantrums, anxiety, and obsessive-compulsive behavior. About 80 percent of boys who inherit Fragile X will have mental impairment ranging severe retardation to low-normal intelligence. The majority are mildly to moderately retarded. Girls are much less affected, with estimates that about 30 percent with this condition have some degree of mental retardation.
Currently, there is no cure for Fragile X, but there are some things that can improve the life of Fragile X victims. In childhood, hyperactivity, tantrums, and anxiety can be heolped by drugs such as Ritalin, Dexedrine or Cylert. For older children, sometimes anti-depressants such as Prozac or Zoloft may be prescribed.
The likelihood of being a carrier of Fragile X syndrome are about 1 in 600. This disease affects approximately 1 in 1,200 people worldwide. Since about 3 percent of the population are considered mentally retarded, this means that Fragile X syndrome accounts for up to 10 percent of mental retardation. It is the most common inherited cause of mental retardation known to exist.
Detection in the carrier is relatively new. In fact, some of the reference books I obtained said there was no way to detect a carrier. However, in 1991, scientists discovered the gene FMR-1 that has led to the development of improved testing for both carriers of the syndrome and those affected. The testing is done by DNA and is a blood test which requires sending blood to a lab which specializes in DNA studies. The test is very accurate and can be used for prenatal diagnosis. In addition, fetal testing can be done through either amniocentesis or earlier in pregnancy through chronic villus sampling.
Personal Interview: Sandra Ursitz, R.N., Nursing Supervisor at Western Center – State Hospital for Mentally Retarded Individuals.
Personal Interview: Sylvia Bartos, M.D., Staff Physician at Western Center – State Hospital for Mentally Retarded Individuals
Smith’s Recognizable Patterns of Human Malformation, Fourth Edition.
Northern California Fragile X Association Newsletter, Winter 1997.
Internet Source: Association for Retarded Citizens, Q;A on Fragile X Syndrome.
Magazine: Exceptional Parent, 1998 Resource Guide, January 1998.
Funk ; Wagnalls New Encyclopedia, 1986 Edition,