Fragile X Syndrome (FXS) is a genetic disorder that causes a range of developmental problems including learning disabilities and cognitive impairment. It is caused by changes in a gene called Fragile X Messenger Ribonucleoprotein 1 (FMR1). FMR1 usually makes a protein that is important for the development of the brain, but in people with FXS, the gene does not function properly, leading to the symptoms of the disorder.

FXS is inherited in an X-linked dominant pattern, which means that the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. The inheritance is dominant if one copy of the altered gene in each cell is sufficient to cause the condition. Males are more severely affected than females, and generally with greater severity.

Common symptoms of FXS include developmental delays, intellectual disabilities, learning and behavioral issues, physical abnormalities, anxiety, attention-deficit/hyperactivity disorder, and/or autism spectrum disorder. There is no cure for FXS, but treatment services can help people learn important skills. Services can include therapy to learn to talk, walk, and interact with others, and medicine can be used to help control some issues, such as behavior problems. It is important that parents understand all options and discuss them with their child’s health care providers.