Early diagnosis of Klinefelter syndrome: the importance of genetic counseling

Introduction Klinefelter syndrome is associated with a numerical abnormality involving the sex chromosomes, and has an estimated prevalence of 1:660 in live male births. We present here a child with karyotype 48,XXXY/49,XXXXY diagnosed early with genetic investigation started at 2 months of age. Case description: Brazilian male patient, 2-month-old child of a non-consanguineous couple, uneventful pregnancy and no history of genetic disease. He was brought in for genetic consultation due to delayed psychomotor development and congenital heart disease, had low birth weight, from the beginning he presented hypotonia, dolichocephaly, ear with low implantation, cryptorchidism, congenital heart disease and camptodactyly. The result of the GTG-banding karyotype examination revealed the mos 48,XXXY[20]/49,XXXXY[70] karyotype, which is compatible with the diagnosis of mosaic Klinefelter syndrome. The early identification of these patients has great relevance for their appropriate treatment and care, especially for minimizing the risks of infertility, feminization and the biopsychosocial implications of Klinefelter syndrome.