Fragile X Syndrome

What is Fragile X Syndrome?

Fragile X syndrome (FXS) is the most common inherited cause of autism and intellectual disabilities. It affects 1 in 4,000 boys and 1 in 6,000 girls worldwide.Fragile X syndrome occurs when a single gene on the X chromosome shuts down. This gene makes a protein needed for normal brain development. In FXS it does not work properly, the protein is not made, and the brain does not develop as it should.

FRAXA Research Foundation

Fragile X syndrome is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males is under 55, while about two thirds of females are intellectually disabled. Physical features may include a Long and narrow face; High-arched palate; Large, protruding ears (both); Hyperextensible finger joints;Hyperextensible (‘double-jointed’) thumbs; Flat feet; Soft skin; Postpubescent macroorchidism (large testicles in men after puberty); and Hypotonia (low muscle tone).


Synonyms of Fragile X Syndrome

  • fragile site, folic acid type, rare, Fra(X)(Q27.3)
  • marker X syndrome
  • Martin-Bell syndrome

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