Symptoms of fragile X syndrome occur due to mutation in the FMR1 gene that is located on the X-chromosome.

What is Fragile X Syndrome?

Fragile X syndrome is an inherited X-linked genetic disorder that results in developmental and intellectual disabilities, along with behavioral problems. It is also called Martin-Bell syndrome or marker X syndrome.

Fragile X Syndrome

Every cell of the body has two sex chromosomes. While a female has two X-chromosomes in each cell, a male has one X and one Y chromosome. Fragile X syndrome occurs due to the mutation in the FMR1 gene that is located on the X-chromosome. Due to this defect, the body cannot produce a protein called fragile X mental retardation1 protein or FMRP that is required for nerve functioning. In some cases, it produces lesser quantities of the same protein.

Though the condition is very rare, men more commonly suffer from the consequences of this mutation. Women are also likely to suffer from less severe forms of the condition.

The clinical features of the patient depend on the extent of the mutation. Individuals with fragile X syndrome, experience mental retardation, autistic-like behavior and hyperactivity. They may have distinctive physical features such as large head circumference, long face with prominent forehead and jaw, protruding ears, lax joints, flat feet, and enlarged testicles in males, especially during puberty. A heart valve defect called mitral valve prolapse may be present.

The characteristic symptoms of fragile X syndrome help to diagnose the condition, which is supported by genetic tests. Treatment is symptomatic and involves supportive care, which include behavioral and occupational therapies.


  1. Fragile X Syndrome - (http://emedicine.medscape.com/article/943776-overview)
  2. The Tarsal Tunnel Syndrome in Hypothyroidism - (http://jnnp.bmj.com/content/46/5/440.full.pdf)

Latest Publications and Research on Fragile X Syndrome

Most Popular on Medindia