What physical examination finding is associated with Klinefelter's syndrome?

Klinefelter's syndrome is a genetic condition that occurs in males who have an extra X chromosome, resulting in a 47,XXY karyotype. A common physical examination finding associated with this condition is gynecomastia, which refers to the abnormal enlargement of breast tissue. This feature arises due to hormonal imbalances, specifically the elevated estradiol levels relative to testosterone. It is often one of the first signs noticed by individuals or identified during physical examinations.

In Klinefelter's syndrome, patients may also present with other characteristics such as tall stature, reduced testicular volume, and infertility, but gynecomastia is a key feature that is readily observable and can help in the early identification of the syndrome. While short stature, low-set ears, and a webbed neck are features associated with other congenital conditions, they are not typically linked to Klinefelter's syndrome. Thus, gynecomastia stands out as the most characteristic physical examination finding for patients with this genetic disorder.