Tetrasomy 21 in an infant with down syndrome and congenital leukemia

A prematurely born infant with the manifestations of Down syndrome and congenital monocytic leukemia was found, by Q and R banding, to have the karyotype 48,XY, +21, +21. This appears to be the first case of tetrasomy 21 documented by banding. Clinically, the infant was indistinguishable from trisomic Down syndrome patients. He died at 4 days of respiratory insufficiency owing to hyaline membrane disease and E coli septicemia.