Fragile X syndrome: an update and review for the primary pediatrician.

Fragile X syndrome (FXS) is the most common inherited cause of mental retardation. Since the initial identification of the responsible gene more than a decade ago, substantial progress has been made in both the clinical aspects of the disorder and its mechanistic basis; hence, it is important for primary care physicians to be familiar with these advances when providing anticipatory guidance. Timely diagnosis allows children to receive early intervention services and families to receive genetic counseling. Here the current state of knowledge is reviewed and a framework is provided for early recognition and diagnosis, along with counseling and treatment implications for the children and family members.