HLA antigens and complement types in patients with intracranial saccular aneurysms.

The occurrence of HLA-A, -B, -C antigens and the HLA controlled complement factors (Bf, C2, C4) was investigated in an unselected group of 116 consecutively admitted patients with intracranial saccular aneurysms, and compared to that of healthy controls (blood donors). When multiplying the p-values with the number of comparisons made, none remained significant. However, a rather high etiologic fraction of the BfS gene (0.59) was obtained. Moreover, for HLA -B7 a significant deviation from the Hardy-Weinberg equilibrium with an increase of homozygotes was found. Due to linkage disequilibria this could indicate a strong association between HLA-DR2 and saccular aneurysms. The presence of HLA-DR2 was therefore investigated in a series of 15 aneurysm patients used as cadaver kidney donors and not included among the 116 consecutively admitted patients. In this group the HLA-DR2 antigen frequency was significantly increased (66.7% vs. 29.7%, p less than 0.01). The present study thus demonstrates an association of saccular aneurysm and the major histocompatibility complex and shows the existence of a genetic predisposition to saccular aneurysm.