Downs Syndrome with 47XX+21/47XX+mar Mosaicism

摘要

A four-year-old girl with typical Down's syndrome is described. She has 47,XX,+21 karyotype in skin and lymphocytes and 47,XX,+mar karyotype in some lymphocytes. Autoradiography and fluorescent analyses have failed to identify the +mar chromosome which has the appearance of a `D' chromosome but which may involve a translocation to a chromosome No. 21. However, the mechanisms of its formation and its significance are not certain.