health

The cause of fragile X syndrome is a mutation in the FMR1 gene on the
X chromosome. Not all children are affected to the same extent by the
mutation, however. Girls who inherit the fragile X may appear normal
or they may have some degree of mental retardation, but usually to a
lesser degree than boys with the syndrome. Between 33 and 50 percent
of girls with fragile X syndrome have significant intellectual impairment;
the rest have either normal intelligence or specific learning disabilities,
such as mathematics. Emotional and behavioral problems occur in children
of either sex. Children with fragile X syndrome have characteristic
physical features as well as developmental and behavioral difficulties.

Physical features:

• Elongated face with large ears
  
• Flat feet
  
• Double-jointed fingers and easily dislocated joints
  
• Poor muscle tone
  
• Excessive curvature of the spine
  
• In males, unusually large testicles

Mental symptoms:

• Mental retardation (IQ between 20 and 70)
  
• Difficulty with speech and language development

Behavioral symptoms:

• Hyperactivity
  
• Some autistic behaviors (poor eye contact, extreme shyness, and
  hand flapping)
  
• Problems paying attention
  
• Aggressiveness
  
• About 20 percent of boys with fragile X meet all the diagnostic criteria
  for autism. Most boys and some girls with fragile X have
  some symptoms of autism; however, many are socially outgoing
  and can form relationships with other people.

Neurological symptoms:

• Anxiety
  
• Depression
  
• Rapidly changing moods
  
• Seizures (about 25 percent)