Fragile X syndrome (patient information)
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| Fragile X syndrome (patient information) | |
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| Location of FMR1 gene | |
| ICD-10 | Q99.2 |
| ICD-9 | 759.83 |
| OMIM | 309550 |
| DiseasesDB | 4973 |
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Fragile X syndrome |
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Fragile X syndrome On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-in-Chief: Alexandra M. Palmer
Overview
Fragile X syndrome, also called Martin-Bell syndrome or Marker X syndrome, is a genetic condition involving changes in part of the X chromosome. It is the leading inherited cause of intellectual disorder and autism spectrum disorder with severe behavioral abnormalities . It is an X linked disorder, affecting both males and females. It is a genetic disease caused by CGG trinucleotide expansion (>200 CGG repeats).
What are the symptoms of Fragile X syndrome?
The physical features of Fragile X syndrome is prominent around the time of puberty. Physical features include:
- Large and protruding ears
- Elongated face
- Macroorchidism (large testicles in men after puberty)
- Flat foot
- High Arched palate
- Hyperflexible finger joints
- Low muscle tone
The common features in child with Fragile X Syndrome include low IQ with learning difficulties (intellectual disabilities). Behavioral abnormalities includes stereotypic movements (e.g., hand-flapping) hyperactivity, inattention, poor social interaction, limited eye contact and poor memory. Child with Fragile X syndrome often presents with developmental delay (including delayed attainment of motor and language milestones). Approximately, 20% of boy with Fragile X syndrome develops seizures (mostly simple or complex partial seizures)
What are the causes of Fragile X syndrome?
Fragile X syndrome is caused by a change in the FMR1 gene. The gene's code is repeated on a fragile area of the X chromosome. The more repeats, the more likely there is to be a problem.
Normally, the FMR1 gene makes a protein you need for your brain to grow properly. A defect in this gene makes your body produce too little of the protein, or none at all.
Boys and girls can both be affected, but because boys have only one X chromosome, a single fragile X is likely to affect them more severely. You can have Fragile X syndrome even if your parents do not have it.
Who is at highest risk?
Since Fragile X syndrome can be inherited, anyone with a family history of the disease is at risk.
How to know you have Fragile X syndrome?
The person will have a family history of Fragile X syndrome (especially a male relative).
There are very few outward signs of Fragile X syndrome in babies. Babies may have a large head circumference. Measurement of oversized testes in males who have reached puberty may also suggest the diagnosis. An experienced geneticist may note subtle differences in facial characteristics. Mental retardation is the hallmark of this condition and, in females, this may be the only sign of the problem.
A specific genetic test called polymerase chain reaction (PCR) is used to diagnose this disease. This test looks for an expanded mutation (called a triplet repeat) in the FMR1 gene.
In the past, a specific type of chromosome analysis was done. Such testing may still be available.
When to seek urgent medical care
Call your health care provider if you suspect the possibility of Fragile X syndrome in a child with mental retardation.
Treatment options
There is no specific treatment for Fragile X syndrome. Instead, effort is directed toward training and education so that affected children can function at as high a level as is possible. Because the condition is not rare, specific educational approaches have been developed and tested.
Diseases with similar symptoms
Where to find medical care for Fragile X syndrome
Directions to Hospitals Treating Fragile X syndrome
Prevention of Fragile X syndrome
Genetic counseling may help prospective parents with a family history of Fragile X syndrome. Genetic testing can help determine the level of risk in such a family. Accurate diagnosis is important because of the possibility of other family members inheriting either Fragile X syndrome or other problems related to an increased number of repeats in FMR1.
What to expect (Outlook/Prognosis)
The outcome depends on the extent of mental retardation.