[Partial trisomy 13 (13q14 leads to 13qter) in mosaic (author's transl)]

A case of partial trisomy 13 with mosaicism in a 6 1/2 year-old boy is reported. Concerning this case and according to previous data in the literature, the authors try to give a precise topology for trisomy 13; it is possible to outline phenotypes specific for a trisomy of both the proximal third and the distal two thirds of the chromosome, but it appears difficult to suggest a more precise picture for the topology of trisomy 13. This difficulty is related to the notion of phenotypic variability encountered in complete trisomy 13.