Fragile x syndrome

Fragile X syndrome (also known as Martin–Bell syndrome, fragile X syndrome, or Renpenning syndrome; Fragile X syndrome) is a hereditary disorder caused by a mutation in the FMR1 gene on the X chromosome.

It is the second most common cause of intellectual disability, after Down syndrome. The disorder is typically transmitted from an unaffected mother to her son. Boys have only one X chromosome, so a mutation on this chromosome results in full manifestation of the disease. Women have two X chromosomes, so a healthy X chromosome can often compensate for the mutated one. The condition leads to characteristic physical features and impaired cognitive development.

Diagnosis:
Diagnosis is based on genetic testing. It primarily affects boys, but in rare cases it can also occur in girls.

• Intellectual disability (mental retardation)
• Impaired learning ability
• Shyness or aggressiveness
• Hyperactivity
• Enlarged testes (macroorchidism)
• High-pitched voice
• Narrow face
• Large ears
• Long lower jaw (mandible)
• Loose joints