[Clinical polymorphism of the XYY syndrome].

The XYY syndrome presents with a wide variation in the clinical features, both of the physical and behavioral nature. We report two new cases which illustrate this statement. The first case presented with aggressive behaviour and cryptorchidism. The second case was associated with pathological short height, pubertal delay and cardiac features (extrasystoles and short PR interval). We revise some of the aspects of XYY syndrome.