Symptoms:

• Delay in crawling, walking, or twisting
• Hand clapping or hand biting
• Hyperactive or impulsive behavior
• Mental retardation
• Speech and language delay
• Tendency to avoid eye contact

Physical signs may include:

• Flat feet
• Flexible joints and low muscle tone
• Large body size
• Large forehead or ears with a prominent jaw
• Long face
• Soft skin

Some of these problems are present at birth, while others may not develop until after puberty.

Family members who have fewer repeats in the FMR1 gene may not have mental retardation, but may have other problems. Women with less severe changes may have premature menopause or difficulty becoming pregnant. Both men and women may have problems with tremors and poor coordination.

Signs and tests:

There are very few outward signs of Fragile X syndrome in babies. Some signs may include:

• Large head circumference in babies
• Mental retardation
• Large testicles after the start of puberty
• Subtle differences in face features

In females, excess shyness may be the only sign of the disorder.

Genetic testing can diagnose this disease.