An XXYY male presenting with aggression: a case report.

An abnormally tall 21-year-old Caucasoid male was referred for psychiatric assessment for pathological aggression and mental subnormality. He showed many of the phenotypic features of Klinefelter's syndrome. Cytogenetic studies revealed a 48,XXYY karyotype. The significance of the association of this karyotype with aggressive behaviour is discussed.