During a routine physical examination, a 16-yearold adolescent boy is found to have only minimal secondary sexual development, gynecomastia, and a tall, eunuchoid habitus. A chromosomal determination on this individual would most likely reveal which of the following?

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The symptoms described are characteristic of Klinefelter syndrome, which is caused by the presence of an extra X chromosome, resulting in a 47, XXY karyotype. The physical description of this boy is that of Klinefelter syndrome. This condition is not usually diagnosed until after puberty when the secondary sexual characteristics do not develop normally. Most of these individuals are 47, XXY but some may have additional X or Y chromosomes.

During a Routine Physical Examination, a 16-Yearold Adolescent Boy Is