Diagnosing genetic anomalies by inspection

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