De novo robertsonian translocation t(21; 21) in a child with down syndrome

Abstract

The phenotypic expression in DS is determined by the type of underlying cytogenetic abnormality. Almost 90-95% cases of DS are due to pure trisomy of the 21st chromosome; 6-7% is the result of mosaicism and in only 3-5% of cases it results from Robertsonian translocation (ROB). About 1/3rd cases of unbalanced Robertsonian translocation causing DS are inherited. We report a 1-year-old-boy with DS secondary to rea(21;21) ROB.