[Klinefelter's syndrome with 48,XXYY (author's transl)].

This paper describes a case of Klinefelter's syndrome with 48,XXYY. Patient had mental retardation and dysmorfic face. Although mental retardation may be recognized early in life, it is difficult to establish a clinical diagnosis of Klinefelter's syndrome before puberty when small testes, gynecomastia and other phisical stigmata may become apparent.