Double autosomal trisomy and mosaicism for three cell lines in man: coexisting trisomy 13-15, trisomy 17-18, and a minority cell line trisomic for a chromosome of both groups.

With few exceptions, the reports of double aneuploidy have concerned individuals with only a single cell line. Hsu and her colleagues de- scribed a child who was a mosaic, with a normal cell line and a doubly trisomic line, trisomic for chro- mosomes 18 and 21. A cell line trisomic for chro- mosome 21 and a second line trisomic for chromo- some 18 were demonstrated in a child reported by Marks et al. (1967). We earlier reported a child who was a mosaic for trisomy 13-15 and trisomy 17-18 (Baikie, Garson, and Birrell, 1965), and it is that case we now describe in detail.