About Fragile X

What is Fragile X?

Fragile X Syndrome is now recognized as the leading hereditary cause of developmental and learning disabilities. Approximately 1/400 individuals in the general population are believed to carry the gene for the condition. Males are usually more severely affected than females.

Boys are typically more severely affected than girls. While most boys have mental retardation, one-half to two-thirds of girls have normal IQ or learning disabilities. Emotional and behavioral problems are common in both sexes.

Fragile X is one of the most common inherited diseases. It affects all races and ethnic groups. 80-90% of people with Fragile X are not yet correctly diagnosed.

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What causes Fragile X?

In 1991, scientists discovered the gene (called FMR1) that causes Fragile X. In individuals with Fragile X Syndrome, a defect in FMR1 (a full mutation) shuts the gene down. Like a defective factory, the FMR1 gene cannot manufacture the protein that it normally makes.

Some indiviuals are carriers: they have a small defect in the FMR1 gene (called a premutation) but do not show symptoms of Fragile X.

Fragile X is inherited. Carrier men (transmitting males) pass the premutation to all their daughters but none of their sons. Each child of a carrier woman has a 50% chance of inheriting the gene. The fragile X premutation can be passed silently down through generations in a family before a child is affected by the syndrome. A DNA blood test identifies both carriers and affected individuals. While the exact prevelance of Fragile X is unknown, recent studies indicate the statistics below:

1 in 2000 boys and 1 in 4000 girls are estimated to be affected



Typical characteristics of Fragile X Syndrome:

Typical Characteristics

Behavioral (may not be seen)

  • Attention Deficit Hyperactivity Disorder
  • short attention span
  • impulsivity
  • hand flapping
  • poor eye contact
  • poor adaptation to changes in routine
  • anxiety
  • resistance to being touched or held
  • Pervasive Developmental Disorder

Childhood Development

  • wide spectrum of cognitive functioning
  • developmental disabilities
  • fine and gross motor delays and sensorimotor problems (extensive service needs)
  • speech and language dysfunction
  • IQs may decline during childhood
  • visual learners (majority)
  • relatively strong imitation skills
  • autistic (up to 15 percent)

Usual Educational Needs

  • speech and language therapy
  • occupational therapy
  • appropriate inclusion program
  • highly structured classroom
  • visual cues to supplement verbal instructions and to teach
  • consistent routine
  • pre-vocational and/or vocational training
  • positive reinforcement of good behavior