Down's syndrome associated with two Robertsonian translocations, 45,XX,−15,−21,+t(15q21q) and 46,XX,−21,+t(21q21q)

A female infant with Down's syndrome was found to be a chromosomal mosaic with two cell lines in both blood and skin cells. One line carried a balanced 15/21 translocation, and the other line was effectively trisomic for chromosome 21 with a 21/21 translocation.