<unk>  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.
48, XXYY
48, XXXX
49, XXXXX
Trisomy 16
Trisomy 22
Trisomy 9
XX gonadal dysgenesis
Partial monosomy 13q