A 27-year-old man and his 24-year-old wife have been trying to conceive a child for 6 years. Physical examination shows he has bilateral gynecomastia, reduced testicular size, reduced body hair, and increased length between the soles of his feet and the pubic bone. A semen analysis indicates oligospermia. Laboratory studies show increased follicle-stimulating hormone level and slightly decreased testosterone level. Which of the following karyotypes is this man most likely to have?

Klinefelter syndrome is a relatively common chromosomal abnormality that occurs in about 1 of 660 live-born males. The findings can be subtle. The 46, X, i (Xq) karyotype is a variant of Turner syndrome (seen only in females), caused by a defective second X chromosome. The 47, XYY karyotype occurs in about 1 in 1000 live-born males and is associated with taller-than-average stature. A person with a mosaic such as 46, XX/47, XX, +21 has milder features of Down syndrome than a person with the more typical 47, XX, +21 karyotype. The 22q11 deletion syndrome is associated with congenital defects affecting the palate, face, and heart and, in some cases, with T cell immunodeficiency.