The 11q;22q translocation: a collaborative study of 20 new cases and analysis of 110 families.

Following a previous collaborative study (Fraccaro et al. 1980), 20 new cases of 11q;22q translocation are described. Twelve families were ascertained through an unbalanced carrier of the translocation and eight cases were ascertained as balanced carriers. A segregation analysis was performed on the 110 families so far published. It was concluded that the 11q;22q translocation is a relatively frequent event, and that all the cases thus far reported might have the same breakpoints at 11q23.3 and 22q11.2. The translocation seems to be independent of environmental factors and it seems to have a low rate of mutation as indicated by the scarcity of de novo cases. The new data confirmed that only one type of unbalanced karyotype (47,XX or XY+der(22)t(11;22)(q23.3;q11.2)) is found among the offspring of the translocation carriers. The minimal overall recurrence risk for an unbalanced translocation was estimated to 2%. There was no difference between the recurrence risks for male and female balanced carriers, while the trend was confirmed of an excess of female balanced carriers among the phenotypically normal offspring of the t(11;22) female carriers.