Fragile X syndrome (FXS) is a genetic condition that causes intellectual disability, behavioral and learning challenges, and various physical characteristics. Though FXS occurs in both genders, males are more frequently affected than females, and generally with greater severity. Life expectancy is not affected in people with FXS because there are usually no life-threatening health concerns associated with the condition.

Prevalence

There have been a number of studies aimed at determining the prevalence of FXS in males and females. Studies have been undertaken both in the “special needs” population and the general population. The agreed upon prevalence of FXS in males is approximately 1 in 3,600 to 4,000 and in females is approximately 1 in 4,000 to 6,000.

The reason it is lower in females is that, while all males with an FMR1 full mutation will have Fragile X syndrome, some females with an FMR1 full mutation will not have behavioral, cognitive, or physical features of FXS.

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Signs & Symptoms

In Males

Behavioral characteristics can include ADD, ADHD, autism and autistic behaviors, social anxiety, hand-biting and/or flapping, poor eye contact, sensory disorders, and increased risk for aggression.

Intellectual disabilities in FXS include a range from moderate learning disabilities to more severe intellectual disabilities. The majority of males with Fragile X syndrome demonstrate significant intellectual disability.

Physical features may include large ears, long face, soft skin, and large testicles (called “macroorchidism”) in post-pubertal males. Connective tissue problems may include ear infections, flat feet, high arched palate, double-jointed fingers, and hyper-flexible joints. No one individual will have all the features of FXS, and some features, such as a long face and macroorchidism, are more common after puberty.

Disposition: They are also very social and friendly, have excellent imitation skills, have a strong visual memory/long term memory, like to help others, are nice, thoughtful people, and have a wonderful sense of humor.

In Females

Behavioral characteristics seen in males can also be seen in females, though females often have milder intellectual disability and a milder presentation of the syndrome’s behavioral and physical features.

Intellectual disabilities: About one-third of females with FXS have a significant intellectual disability. Others may have moderate or mild learning disabilities, emotional/mental health issues, general anxiety, and/or social anxiety.

A small percentage of females who have the full mutation of the FMR1 gene that causes FXS will have no apparent signs of the condition—intellectual, behavioral, or physical. These females are often identified only after another family member has been diagnosed.

Source: National Fragile X Foundation