Trisomy 12 mosaicism in a 7 year old girl with dysmorphic features and normal mental development.

We present the case of a mentally normal 7 year old girl with short stature, scoliosis, atrial septal defect, and dysmorphic features including linear pigmented streaks on the forearms and lower legs. Chromosome analysis of cultured fibroblasts showed trisomy 12 in 9% and 13% of cells from two skin biopsies. Two trisomy 12 cells were found in lymphocytes after analysis of 500 metaphases. Her clinical features are compared with those of other liveborn cases of trisomy 12 mosaicism and the problems of prenatal diagnosis of such an abnormality are discussed.