Cardiac malformations in relatives of children with truncus arteriosus or interruption of the aortic arch.

Familial recurrence risks for congenital cardiac malformations have been estimated at 1 to 4%, but little is known of recurrence risks for uncommon congenital cardiac malformations. This study determined the incidence of congenital cardiac malformations in relatives of patients with either truncus arteriosus (TA) or interruption of the aortic arch (IAA) seen between 1955 and 1985. Prior to this study, only 2 cases of IAA in siblings had been reported and the recurrence risk of TA had been estimated at 1.2%. In the families of 36 index cases of IAA, there were 98 siblings, 2 with congenital cardiac malformations (2.1%). All recurrences were in IAA type B families. Single cases of congenital cardiac malformations were found in second- and third-degree relatives and 2 cases in more distant relatives. In the families of 49 index cases of TA, there were 106 siblings, 7 with congenital cardiac malformations (6.6%). Two had TA, 3 had other conotruncal anomalies and 2 had other congenital cardiac malformations. Two parents had congenital cardiac malformations, 1 with TA and 1 with conotruncal malformation. Among second- and third-degree relatives, 7 had congenital cardiac malformations (5 were conotruncal, including 1 half sibling). Among greater than third-degree relatives, 3 had congenital cardiac malformations. Thus, in IAA, the recurrence rate of congenital cardiac malformations (2.1%) was higher than expected and could be related to the etiology of IAA type B as a conotruncal malformation. In TA, the recurrence rate of congenital cardiac malformations was 6.6%, higher than previously reported. When TA was complex the recurrence risk was higher (13.6%). These findings must be taken into consideration for satisfactory genetic counseling.