Central precocious puberty in 48,XXYY Klinefelter syndrome variant.

We report the first case of central precocious puberty in a patient with 48,XXYY Klinefelter syndrome variant. We also report clinical characteristics, growth pattern, endocrine data and pathological testicular findings. The patient did not receive medical care for his precocious pubertal development, because of adequate height prognosis, and reached normal height for both his target height and Klinefelter patients. Since precocious puberty seems to occur in Klinefelter syndrome and its variants, we advise karyotype analysis in boys with mental retardation, gynecomastia, small testes and precocious onset of puberty.