[The 49,XYYYY syndrome: apropos of a case detected at birth and followed for 2 1/2 years].

A male child, mentally and physically retarded shows a facial dysmorphy, fingers' abnormalities and a radio-ulnar synostosis. These features are common in the 49,XYYYY syndrom, in which external genitalia, normal at birth, remain undevelopped at the time of puberty. Four others publications through the literature report tetrasomic cells for Y chromosome, but only two of them are real 49,XYYYY (with 88% to 100% of affected cells). Our case has 96,7% tetrasomic cells.