Fragile X syndrome
Fragile X syndrome an X-linked disorder caused by expansion of the CGG trinucleotide repeat affecting the Fragile X mental retardation 1 (FMR1) gene on the X chromosome. X-linked dominant – males are more severely affected by this disorder than females. It is the most common inherited form of mental retardation and second only to Down’s syndrome as a cause of mental impairment. Mothers of affected patients are obligate gene carriers.
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Findings
- Learning disabilities (mental retardation) and cognitive impairmentWikimedia Image author: Peter Saxon
- Language delay, echolalia
- Large, protruding ears
- Long face
- Large Jaw
- Large testes (Macroorchidism) at puberty
- Hyperextensible finger joints
- Hyperextensible (‘Double-jointed’) thumbs
Diagnosis
DNA probe to pinpoint the defective gene
Other Names
- fra(X) syndrome
- FRAXA syndrome
- FXS
- marker X syndrome
- Martin-Bell syndrome
- X-linked mental retardation and macroorchidism
MCQ Point
Fragile X syndrome is associated with the following characteristics)
a) More common in boys
b) Most common form of inherited mental retardation
c) Involves the long arm of the X chromosome
d) Can be diagnosed with a blood test
e) Treatment is limited to symptomatic management