Overview
Fragile X syndrome describes a set of features seen due to a trinucleotide repeat disorder in the fragile X mental retardation (FMR1) gene found on the X chromosome (Xq28).
Epidemiology
- Fragile X syndrome affects up to 1 in 5000 men and 1 in 4000 women
- Up to 4 times as many women carry the gene abnormality as men
Presentation
Features in males tend to be more prominent as they do not have two copies of the X chromosome:
- Large, low set, and protruding ears
- Long, thin face and high-arched palate
- Hypotonia
- Macroorchidism
- Learning difficulties
- Hyperextensible fingers, soft skin, flat feet
- Mitral valve prolapse
Females with one fragile X chromosome and one normal X chromosome may be unaffected or have mild features.
