Symptoms

Aside from intellectual disability (mental retardation), prominent characteristics of the syndrome include an elongated face, large or protruding ears, large testicles (macroorchidism), and low muscle tone. Behavioral characteristics may include stereotypic movements (e.g., hand-flapping) and atypical social development, particularly shyness and limited eye contact.

Some individuals with the fragile X syndrome also meet the diagnostic criteria for autism. While full mutation males tend to present with severe intellectual disability, the symptomology of full mutation females runs the gamut of minimally affected to severe intellectual disability, which may explain why females are under diagnosed relative to males.