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Inherited Disorders and Birth Defects

Fragile X inheritance

09/19/2007

Question:

Can the disposition to possibly have Fragile X be passed to grandchildren from their grandmother? I suspect that is a problem we have, so I was tested & the number of repeats I had was 20-30, so they said that was normal. Because of the fact that I started menopause at 37, plus many problems with male children in my family, as well as scoliosis, I thought it could be Fragile X. So can that be passed to them from their grandmother? Thanks.

Answer:

Fragile X syndrome is caused by an abnormal change in a gene called FMR1. In people who have fragile X syndrome, a defect in FMR1 (a "full mutation"- more than 200 repeats) shuts the gene down. Like a defective factory, FMR1 cannot manufacture the protein that it normally makes. Other individuals are carriers: they have a small defect in FMR1 (called a "premutation" - ~40-200 repeats) but do not usually show symptoms of fragile X.

Symptoms of fragile X syndrome include: mental impairment, ranging from learning disabilities to mental retardation, attention deficit and hyperactivity, anxiety and autistic-like behaviors. Other features seen in older children are a long face, large ears, flat feet, and hyperextensible joints, especially fingers. Boys are typically more severely affected than girls. Intellectual abilities in girls can range from having a normal IQ or learning disabilities to mental retardation. Emotional and behavioral problems are common in both sexes.

Women who are carriers of the "premutation" and have more than 40 repeats may have an increased chance of having premature menopause. However, early menopause can happen for other reasons.

A woman who has the normal number of repeats, 5-40, is not a carrier for the mutation that causes fragile X so would not be able to pass it on to any of her children or grandchildren. However, there may be other reasons for family members to have problems that can run in families or be inherited.

As you have been tested for fragile X, if you have not already talked to a geneticist or genetic counselor about your test results, I would highly recommend that you do. You can ask your doctor for a referral or you can locate a genetics center near you at the National Society of Genetic Counselors' Resource Center's website below.

Related Resources:

National Society of Genetic Counselors Resource Center

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University