The XYY condition in childhood: clinical observations

The 47,XYY chromosome complement was found in the lymphocytes of a 6-year-old white boy of average intelligence. He seems well adjusted to home and school environments. He is extremely tall for his age, has an articulation problem, impaired coordination, and muscular and skeletal anomalies. Although he has had a hydrocoele repaired, his genitalia are otherwise normal. Mental retardation and genital maldevelopment have been quite common in the few reported cases of the XYY condition in children, but this may be partially due to sampling methods. It is apparent that the mental and physical characteristics of the average XYY boy are yet to be determined.