Robertsonian translocations and abnormal phenotypes. Groupe de Cytogénéticiens Français.

The Groupe de Cytogénéticiens Français collected 32 cases of Robertsonian translocations with an abnormal phenotype of which 21 t(13q;14q)'s. Nineteen were inherited, four had had occurred de novo; and nine were of unknown origin. The 21 t(13q;14q)'s were grouped according to the phenotype. Some suggested partial 13 trisomy (hexadactyly; eye defect), others partial 13 monosomy (facial dysmorphism; thumb anomalies). Three de novo t(15;15)'s with Prader-Willi syndrome show that non identifiable partial monosomies may be associated with the occurence of Robertsonian translocations. The mechanism leading to the fusion of accrocentrics are discussed.