XYY Karyotype in a Case of Familial Hypogonadism

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Abstract
Two brothers are described who showed the clinical picture of hypogonadism with seminiferous tubule dyagenesis, gynecomastia and elevated urinary gonadotrophins resembling Klinefelter''s syndrome. Chromosome preparations were made of cells from peripheral blood and skin. Instead of the XXY chromosome complement usually associated with this syndrome, an XXY karyotype was found in one of the brothers, while the other presented the normal male chromosome pattern. A sister, who was possibly also hypogonadal, had a normal female karyotype. Labeling studies of the chromosomes of the XYY patient showed that the 2 Y chromosomes/ replicated similarly and later than the other members of the G group. XYY karyotype has previously been reported in only 11 cases. A review of these cases showed that, although the incidence of hypogonadism and other genital abnormalities was high, no consistent clinical picture was associated with this chromosome pattern. The significance of the extra Y chromosome in 1 of the 2 patients here described is not known.