SIBLING RISKS OF ABDOMINAL AORTIC-ANEURYSM

There is evidence that the risk of abdominal aortic aneurysm (AAA) is greater in first-degree relatives of patients with the disorder than i n the same age group of the general population. We conducted a 3-year study of siblings of AAA probands and siblings of a control group (cat aract surgery patients) of the same age. Genetic information was obtai ned by interview from 126 probands and 100 controls; another family me mber was present at the interview. Medical records were obtained and f urther information verified before a sibling (over age 50) was assigne d affected status. Of 427 siblings of probands, 19 (4.4%) had probable or definite AAA, compared with five (1.1%) of 451 siblings of control s. The lifetime cumulative risks of AAA at age 83 were 11.7% (SD 3.1) and 7.5% (4.1), respectively. The risk of AAA began at an earlier age and increased more rapidly for probands' siblings than for controls' s iblings (p<0.01, log-rank test). A risk comparison, based on the resul ts of ultrasound screening of 54 geographically accessible siblings of probands and the 100 controls showed a similar pattern. Ten (19%) sib lings of probands and eight (8%) controls had AAA on ultrasound (lifet ime cumulative risk 60.8% [18.9] vs 14.9% [5.1], p=0.01). These result s show that familial factors influence the age of onset of AAA. We rec ommend routine ultrasound examination of siblings of patients with AAA .