[Association of trisomy 21 and gonosomal trisomy. Apropos of 2 cases].

The existence of double autosomal trisomy is exceptional in a newborn child: --Down syndrome and trisomy 18. --Down syndrome and trisomy 13. On the other hand, the association of an autosomal trisomy, generally Down syndrome with gonosomal trisomy, is less rare with an extra X (triplo X, Klinefelter) or an extra Y. The association of Down syndrome with Turner XO syndrome (autosomal gonosomal association) doesn't insert in the subject, and has been described only once in the literature.