Commonly referred to as the Martin-Bell syndrome or the Marker X syndrome, Fragile X is the most common form of inherited mental handicap in boys and a significant cause in girls. The inheritance is different from common dominant or recessive inheritance patterns.

A fragile area on the X chromosome tends to repeat bits of the genetic code. The more repeats, the more likely there is to be a problem. Boys and girls can both be affected, but because boys have only one X chromosome, a single fragile X is more likely to affect them.

Signs of Fragile X Syndrome:

  • Family history of fragile X syndrome or mental handicap
  • Mental handicap
  • Large testicles
  • Tendency to avoid eye contact
  • Hyperactive behavior
  • Large forehead and/or ears with a prominent jaw