Mosaic tetrasomy 21 in a liveborn male infant

Abstract
A male infant with several clinical signs of Down syndrome, but with additional features not usually seen in that syndrome, was found to have a 47, XY, t(21;21) karyotype in all skin fibroblasts examined. The same karyotype occurred with very low frequency and together with a normal cell line in blood lymphocytes. We have been unable to find reports of a similar case.