Fragile X syndrome is the most common form of inherited developmental disability. A problem with a specific gene causes the disease. Normally, the gene makes a protein you need for brain development. But the problem causes a person to make little or none of the protein. This causes the symptoms of Fragile X.
People with only a small change in the gene might not show any signs of Fragile X. People with bigger changes can have severe symptoms. These might include
A genetic blood test can diagnose Fragile X. There is no cure. You can treat some symptoms with educational, behavioral, or physical therapy, and with medicines. Getting treatment early can help.
NIH: National Institute of Child Health and Human Development