OCCURRENCE OF CARDIAC-MALFORMATIONS IN RELATIVES OF CHILDREN WITH TRANSPOSITION OF THE GREAT-ARTERIES

Transposition of the great arteries (TGA) is the most common cyanotic cardiac malformation, representing 5-7% of all cardiac malformations. Previous estimates of the frequency of cardiac malformations in sibs o f probands range hom 0-1.7%. This study ascertained the frequency of c ongenital cardiac malformations in relatives of 271 probands with TGA, who mere grouped according to the type of TGA present. These include dextro (d-TGA), levo (l-TGA), complex TGA, and asplenia with TGA. In t he d-TGA cases there were 369 sibs, one of whom had a cardiac malforma tion (0.27%). There were 50 sibs in the l-TGA group, with one sib havi ng a cardiac malformation (2.00%). Cardiac malformations were found in 2 of 143 (1.40%) sibs of the complex TGA index cases, and 1 of 50 (2. 00%) sibs in the asplenia with TGA group. The overall recurrence risk of cardiac malformations in sibs of TGA probands was 0.82%. Cardiac ma lformations in parents of probands were found in 0.29% of d-TGA, 0% of l-TGA, 1.54% of complex TGA, and 0% of asplenia with TGA, giving an o verall parental occurrence of 0.55%. This is the first study to provid e information on the different types of TGA in evaluating sib occurren ce. It provides necessary genetic counseling information for families of probands with TGA. (C) 1996 Wiley-Liss, Inc.