Familial small supernumerary marker chromosome (sSMC) (14)(:p11-q11:) in a child with translocation down syndrome.

We report a case of familial small supernumerary marker chromosome (sSMC) in a child with translocation Down syndrome (DS)and mother.The GTG-banded chromosomal analysis of DS child revealed 47,XY,+21,+mar and mother karyotype was 47,XX,+mar.The GTG-banded sSMC had a similar morphology of small acrocentric chromosomes .Fluorescence in situ hybridization (FISH)evaluation of sSMC using centromere probes(13/21,14/22,22)confirmed sSMC as derivative chromosome 14.The sSMC was not specifically stained with whole chromosome paint and arm-specific probes for chromosome 14;thus it has been described as der(14)(:p11-q11:).The phenotypic changes were not evident, may be due to trisomy condition in the child or the sSMC contain repetitive sequences.