Fragile X Syndrome

Fragile X Syndrome is indexed under Pediatric-Onset Chronic, Genetic/Chromosomal. Also known as FXS.

US prevalence

NIH/NICHD has cited approximate frequencies of 1 in 4,000 males and 1 in 8,000 females; this is a frequency estimate, not a current U.S. patient count Source: NICHD — Centers for Collaborative Research in Fragile X. This figure comes from a professional society, registry, or study rather than a federal source. Label: REPORTED.

ICD-10-CM codes

Q99.2

Typical onset

Present at birth; diagnosed in childhood

Course

lifelong

Body systems

neurological

Sex differences

Males more severely affected (X-linked)

Racial and ethnic differences

Pan-ethnic

What this page does not establish

These figures describe populations, not individuals, and none of them is a diagnosis or a treatment recommendation. Prevalence estimates are approximate and reflect published ranges. Disparity figures are reported patterns, not causes.

Taxonomy last reviewed 2026-05-19. Each figure on the interactive page carries its own source and retrieval date, which can be later than this review.

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