Abstract

Complex small supernumerary marker chromosomes sSMCs consist of chromosomal material derived from two or more different chromosomal regions and constitute one of the smallest subsets of sSMC Most of complex sSMCs are represented by a der 22 t 11 22 in Emanuel syndrome As far as we know only one recent report has described sSMCs involving simultaneously X and Y chromosomes in Turner Syndrome We report two patients a female and a male both with a complex sSMC derived from X and Y chromosomes in mosaic with a 45 X cell line In both patients the marker chromosomes were early replicating and the XIST gene was absent FISH and PCR confirmed the presence of Yp loci TSPY AMGY SRY DYZ3 and negative for DYZ1 The DAZ4 sequence was present only in patient 1 Our findings suggested that complex sSMC involving X and Y chromosome could be a kind of sSMC of the gonosomes