Diagnosing genetic anomalies by inspection.

Several readily identifiable syndromes that have a genetic basis consist of mental retardation, hyperactivity or other abnormal behaviors, and characteristic physical signs. These disorders are not only an opportunity for clinical diagnosis, but they reflect the neurologic underpinning of intellect and behavior. Moreover, the wide variations in their phenotypes suggests that genetic testing be considered in children with abnormal appearance and mental retardation.