Fragile X Syndrome (FXS) is an inherited intellectual disability that causes developmental delays, learning disabilities and emotional instability, including anxiety, depression and impulsive behavior. Fragile X results from a mutation in a single gene called Fragile X Mental Retardation Gene 1 (FMR1).
FXS symptoms usually appear when children are infants or toddlers. According to the National Institutes of Health, the average age of diagnosis for boys is 36 months and 42 months for girls. The syndrome is more common in males than females, and males usually have more severe symptoms. About one third of those with FXS have features of autism spectrum disorder. Most males with the syndrome and some females have physical symptoms, as well, such as a long and narrow face, a prominent forehead and jaw, drooping ears and flat feet. Other manifestations of the syndrome include hyperactivity, tantrums, and in some cases, seizures.
After puberty, males with FXS may have enlarged testes. Females may have difficulty conceiving or enter menopause early. Pregnant women with a known FMR1 gene mutation are encouraged to undergo prenatal testing to determine if the fetus has FXS, enabling early therapeutic intervention.
According to the National Fragile X Foundation, “Children with FXS tend to have maladaptive behaviors (tantrums, screaming, trying to flee a situation or panic) when their brains and bodies move into fear/fight or flight following a triggering event. The hyperarousal leads to a disorganized state with decreased self-regulation, decreased access to language and communication and reduced attention. Once this process begins, it can be hard to avoid an explosive outburst.”