Follow-up 20 years later of 34 Klinefelter males with karyotype 47,XXY and 16 hypogonadal males with karyotype 46,XY.

A 20-year follow-up study of 50 hypogonadal males has been made. Of these 34 had Klinefelter's syndrome with the karyotype 47,XXY and 16 had the karyotype 46,XY. These males have been examined at mean ages of 27 and 37 and in the present study at a mean age of 47. At the first examination the following conditions were found in the Klinefelter males to a significantly higher degree than in the hypogonadal males with 46,XY: immaturity, below average school performance, few or no friends, previous mental illness, little energy and initiative, few or no spare time interests, occupation as an unskilled labourer. Psychological testing showed a full scale IQ of 103 in the Klinefelter males and 115 in the hypogonadal males. The follow-up studies have shown that in spite of these findings the Klinefelter males have managed far better than could have been expected at the time of the first investigation. The improvement in a number of conditions such as mental health, working capacity, social adjustment, relations with other people, and activity level was considerable between the ages of 27 and 37. The present examination shows a further improvement at the age of 47 with the only significant difference between the Klinefelter males and the hypogonadal males with 46,XY being a higher frequency of single Klinefelter males. The present examination also showed that there was no significant difference between the two groups in occupation, working capacity, social adjustment, mental and physical disorders or criminality. The results of the examination at the mean age of 27 would probably have been considerably more favourable for the Klinefelter males if diagnosis had been made in childhood, and information, counselling, support and hormone treatment had been given from an early age. The fact that the great majority of the Klinefelter males have managed quite well in spite of this and that no remarkable differences were found between them and a control group is of great importance for genetic counsellers, especially for prenatal counsellers. Up until now, in 75% of cases in which sex chromosome abnormalities, including Klinefelter's syndrome, have been diagnosed prenatally in Denmark abortion has been induced. We believe this is mainly due to insufficient information about the many positive aspects of the development of individuals with sex chromosome abnormalities.