In the last decade there has been a significant increase in the proportion of XYY males detected prenatally, mostly as a fortuitous finding. It is of utmost importance to obtain a clear idea of the developmental profile of boys with karyotype 47,XYY and of possible problem areas during further development in order to inform the parents correctly during pregnancy and to provide an adequate surveillance later on. In this study we observed 38 XYY males, of which 12 were diagnosed prenatally. We found that these patients are at considerably increased risk for delayed language--and/or motor development. From birth on, weight, height and head circumference are above average values. The majority attends kindergarten in the normal education circuit although in 50% of the cases psychosocial problems are documented. From primary school age on, there is an increased risk for child psychiatric disorders such as autism. Moreover, although normally intelligent, many of these boys are referred to special education programmes.

We describe the findings of XYY syndrome in the setting of encountering an individual with this particular condition in the endocrinology clinic. XYY syndrome is a relatively frequent if unfamiliar condition, which is characterized by taller than average height. The extra Y chromosome may play a role in determining the height of these individuals. From this case, a differential diagnosis of tall stature is outlined, in addition to a description of the principal syndromes associated with gigantism. These primarily include Klinefelter syndrome, Marfan syndrome, androgen resistance and growth hormone excess. These various entities are described from the point of view of their symptomatology, biology, pathophysiology and therapeutic characteristics.

The psychological test results of five XYY males from in a population study showed an intellectual level within the normal range but with a mean full scale IQ and educational level lower than expected. The cognitive as well as emotional function was characterized by immaturity, manifested in passivity, unreflectiveness and emotional liability, in three resulting in uncontrolled aggressive outbursts. Conflict material also appeared immaturely resolved, centering around unfulfilled needs of contact and insecure masculine identification. The defense mechanisms used were generally rather weak, but only in one subject did the anxiety level seem to be excessively low. All five males differed to a certain extent from their siblings; three of them were hyperactive, restless, hot-tempered and impulsive at school and four of them had difficulties at school. Three learned a trade, but only one stayed in his trade, and one was applying for disablement pension on account of personality deviation. Two of the five had a criminal record. It is concluded that the presence and degree of the above-mentioned characteristics of XYY males varied. It is evident that environmental factors play as great a role for the development of personality and behaviour in males with karyotype 47, XYY as in males with a normal chromosome constitution.