Fragile X syndrome (FXS), or Martin-Bell syndrome, is a genetic syndrome which results in a spectrum of characteristic physical and intellectual limitations and emotional and behavioral features which range from severe to mild in manifestation.
Frequency
Conservative estimates report that fragile X syndrome affects approximately 1 in 4000 males and 1 in 8000 females.
Pathology
The symptoms of fragile X syndrome are caused by abnormalities in DNA on the X chromosome. Examination of the karyotype reveals a constriction at the end of the long arm of the X chromosome, followed by a thin strand of genetic material. The constriction and thin strand give the appearance of a fragile portion of the X chromosome. Sequencing of the genetic material reveals a repeating base pair triplet that is responsible for the syndrome.
Symptoms and Signs
People with fragile X syndrome have physical, cognitive and behavioral abnormalities. They have large, protuberant ears; a prominent chin and forehead; a high arched palate; and, in postpubertal males, macroorchidism. The joints may be hyperextensible, and heart disease (mitral valve Continue reading »
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