Fragile X Syndrome : Symptoms

by National Institute of Health

(Page 3 of 9)

Because mothers pass on only X chromosomes to their children, if the mother has the altered gene for Fragile X, she can pass that gene to either her sons or her daughters. If the mother has the mutated gene on one X chromosome and has one normal X chromosome, and the father has no genetic mutations, all the children have a 50-50 chance of inheriting the mutated gene.

The odds noted here apply to each child the parents have. Having one child who receives an X chromosome with the FMR1 mutation does not increase or decrease the chances of having another child with the mutated FMR1 gene. Nor do these odds influence the severity of the symptoms. Having one child with mild symptoms does not mean that the other children will have severe symptoms, and having a child with severe symptoms does not mean that other children will have mild symptoms.

A premutation gene is less stable than a full mutation. In some cases, the mutated gene may expand from the premutation to the full mutation as it is passed on from mother to child. The chances of expansion depend on the number of repeats in the promoter of the premutation gene; the higher the number of repeats, the more likely it is that the gene will expand. These chances also increase with each generation. Children of a mother who has the premutation, then, may have no genetic mutation, the premutation, or the full mutation.

Further, because an altered FMR1 gene can be passed on without symptoms, many people are unaware that they have it. As a result, a premutation form of the FMR1 gene can be silently passed through a family for generations, with no one ever showing any symptoms. However, with each generation, it becomes more likely that the premutation gene will expand its number of repeats to become a full mutation gene, which would also increase the number of and seriousness of symptoms.

What are the signs and Symptoms of Fragile X syndrome?

Not everyone with Fragile X has the same signs and symptoms, or to the same degree. Even affected children in the same family can have different signs and symptoms. These differences often make Fragile X hard to diagnose. However, because everyone with Fragile X has too little FMRP, they do share a pattern of certain physical, social, mental, and sensory characteristics. Although most of the Fragile X research to date has focused on children, adults with Fragile X also have most of these signs and symptoms.

In general, the signs and symptoms of Fragile X fall into five categories:

• Intelligence and learning
• Physical
• Social and emotional
• Speech and language
• Sensory

Now consider each category in more detail.

Intelligence and learning

Many people with Fragile X have impaired intellectual functioning, which affects their ability to think, reason, and learn. In most cases, researchers use an intelligence test to measure intellectual functioning, resulting in an IQ (intelligence quotient) score. But this score reflects many things besides the ability to think. Attention disorders, hyperactivity, anxiety, and language processing problems can interfere with test-taking skills and learning. Because many people with Fragile X have these problems, a person with Fragile X may have more capabilities than his or her IQ score suggests.

Researchers consider people who score between 85 and 115 on an IQ test to have "average" intelligence. On the whole, less than 20 percent of males with Fragile X have an IQ in this range. At the same time, few people with Fragile X are severely or profoundly impaired, with IQs below 40 or 25, respectively. In general, those with a full mutation tend to have an IQ somewhere in between 40 and 85, which is considered mild to moderate mental impairment.

Females tend to be less seriously affected by Fragile X than males. Even among females who have full-mutation FMR1 genes, only about one-third have an IQ in the mental retardation range. Females with Fragile X are more likely to have relatively normal cognitive development, or they may show a learning disability where their academic achievement in some areas is lower than their overall ability to learn. For example, a female with a learning disability in math might score several grades below her grade level in math, even though her IQ is within the normal range.

Many factors influence intelligence, and, like most individuals, people with Fragile X have areas of both strength and weakness. For example, people with Fragile X tend to have good memories for pictures and visual patterns. This ability helps them to learn to recognize letters and words. They are also generally able to follow instructions that are presented as pictures. Their main weaknesses are in thinking about abstract ideas, organizing information, planning ahead, and solving problems.

No matter what their IQ or areas of intelligence, all children and adults with Fragile X are capable of learning. Most children will progress in school and develop basic academic skills. Many adults can learn to take care of themselves and work at a job. People with Fragile X may need more time to learn, special teaching methods, or a specially tailored environment, but they usually can and do make steady progress.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.