XYYYY syndrome
RARE CHROMOSOMAL DISORDER
49,XYYYY
XYYYY syndrome, also known as 49,XYYYY, is an exceptionally rare chromosomal disorder in which a male has three additional copies of the Y chromosome. Only seven non-mosaic cases of the disorder have ever been recorded in the medical literature, as well as five mosaic cases, of which two had more 48,XYYY than 49,XYYYY cells.