Double autosomal trisomy: case report (48, XX, +18, +21) and review of the literature.

A twelve-months-old female is reported with double trisomy of the autosomes 18 and 21 (48,XX,+18,+21), exhibiting the clinical features of mongolism. The findings of this patient and the data of fourteen previously reported cases with double autosomal trisomy, twelve of them mosaics, may be summarised as follows: The mean birth weight was lower than in the single trisomies D, E, and G. The distribution of the maternal ages at birth of the patients was striking: six mothers were younger than 21 years, seven mothers were older than 34 years. In those patients with prevalence of one of the two extra chromosomes in their karyotypes, the corresponding trisomy syndrome also predominated clinically. In those cases with an equal proportion of both additional chromosomes there were as many patients with clinical predominance of the one as of the other trisomy syndrome. Survival beyond the second half of the first year of life was seen only in those patients who showed the clinical picture of mongolism.