Derivative chromosome 11 in a child resulting from a complex rearrangement involving chromosomes 3, 6 and 11 in father: Significance of parental karyotyping
The proband, a 3-year-old, morphologically normal male child born from full-term normal delivery to a phenotypically normal couple presented with a clinical history of mental retardation with convulsion, and was referred for cytogenetic analysis. The couple had a history of two first-trimester spontaneous abortions. However, there was no prior family history of congenital anomalies or other inherited disorders. The abortuses from earlier pregnancies were not subjected to cytogenetic analyses. Cytogenetic analysis was carried out on phytohemagglutinin stimulated peripheral blood lymphocytes, cultured in Roswell Park Memorial Institute (RPMI) 1640 medium, using modified standard protocol.[] Twenty G-banded metaphases were analyzed using Cytovision software, and designated as per ISCN (2009) nomenclature at 550 bands per haploid genome.\nThe karyotype of G-banded metaphase of the proband revealed derivative chromosome 11 arising from the presence of additional material of unknown origin on the short arm of chromosome 11 at band 11p15.2. To ascertain the origin of derivative chromosome identified in the child, the parental samples were requested for cytogenetic studies. Mother had an apparently normal karyotype (46, XX) reported earlier. The karyotype of father revealed a CCR involving chromosomes 3, 6, and 11, the breakpoints being 3p22, 6p22.1 and 11p15.2 respectively, with the karyotype representation as 46, XY, t(3;6;11) (p22;p22.1;p15.2) as depicted in []. This was an apparently balanced translocation since the father had no phenotypic features. Hence, the final karyotype of the child was designated as 46, XY, der(11) t(6;11)(p22.1;p15.2)pat, indicating partial trisomy for 6p22.1-pter and monosomy for 11p15.2-pter. The derivative chromosome 11 from father had directly passed to the child, resulting in unbalanced karyotype in child.