Fragile X syndrome (FXS), the most common form of inherited mental retardation, results from a mutation that silences transcription of the fragile X mental retardation gene (FMR1), thus preventing translation of the FMR1 protein (FMRP). FMRP produces the symptoms of FXS.

Individuals with FXS have a highly variable level of cognitive disability, typical physical features such as large ears and a long face, and behavioral dysfunction including hyperactivity, anxiety, perseveration, tactile defensiveness and behavior similar to that of individuals with autism. Common medical problems include gastroesophageal reflux, otitis media and sinusitis, orthopedic problems, hypotonia, mitral valve prolapse, seizures and sleep disorders.

Diagnosis of FXS by DNA analysis is important to provide targeted treatment for the patient and appropriate genetic counseling for the family. Supportive strategies to maximize functioning include aggressive management of medical problems, educational programming tailored specifically for the FXS cognitive profile and medications targeting problematic behaviors.

FMRP appears to be involved in regulating connections between neurons (brain cells). Insights into the specific functions of FMRP in the brain may soon lead to new therapies to improve cognitive functioning.