Learning more about fragile X.

Fragile X syndrome is a genetic condition caused by a full mutation of the FMR1 gene. The FMR1 gene typically produces a protein called the fragile X mental retardation protein [FMRP], which is necessary for normal brain development; people with fragile X do not produce the protein.

Fragile X is the most common inherited intellectual and developmental disability, and is the most common known genetic cause of autism. About 1.5 million Americans have the gene permutation, and an estimated 100,000 Americans have fragile X syndrome. About one-third of individuals with fragile X exhibit behaviors consistent with an autism diagnosis.

Some more facts about fragile X:

Fragile X can affect a child’s learning, behavior, appearance, and health. Symptoms may be subtle or severe.

Signs a child might have fragile X include:

  • Developmental delays, like not sitting, walking, or talking at the same time as other children the same age;
  • Difficulty learning new skills;
  • Avoiding eye contact;
  • Hand flapping;
  • Temper tantrums;
  • Poor impulse control;
  • Trouble paying attention;
  • Hyperactivity;
  • High anxiety in new situations; or
  • Extreme sensitivity to light or sound.

Some children with fragile X also have differences in their appearance, including:

  • A large head;
  • A long, narrow face;
  • A large forehead and chin;
  • Large ears;
  • Loose joints; or
  • Flat feet.

Fragile X affects more boys than girls – 1 in 4,000 males vs. 1 in 6,000 females – and it often affects boys more seriously than girls:

  • Girls typically experience milder symptoms overall than boys, and some girls show no signs at all;
  • While most boys experience learning and developmental disabilities, most girls don’t have these issues;
  • Boys can display aggressive and self-destructive behavior due to fragile X; and
  • Boys can have enlarged testicles post-puberty due to fragile X.

Fragile X syndrome can be detected with a simple DNA blood test. The blood test is extremely accurate, widely available, and can be ordered by any doctor. It can detect carriers as well as fully affected individuals.