48, XXYY

Overview
48, XXYY syndrome is a sex chromosome  anomaly.

It was previously considered to be a variation of Klinefelter's syndrome. It is still considered a part of the syndrome by some definitions.

Incidence
It affects one in every 18,000-40,000 male births.

Presentation
Common features include tall stature, gynecomastia,  truncal obesity, skin ulcers, and a craniofacial dysmorphism described  as a "pugilistic" facial appearance.

History
The first published report of a boy with a 48,XXYY karyotype was by Sylfest  Muldal and Charles H. Ockey in Manchester, England in 1960. It was found in a 15-year-old mentally challenged boy who had signs of  Klinefelter syndrome; eventually, it appeared that he didn't have the  Klinefelter Syndrome but, as shown above, the XXYY syndrome.