IL18 and temporal arteritis: It was due to a significantly increased frequency of homozygosity for the IL18 -607 A/A genotype in the group of patients with biopsy-proven GCA compared with controls (20.4% versus 13.8 in patients and controls, respectively; IL18 -607 A/A homozygous versus IL18 -607 C/A plus IL18 -607 C/C: P = 0.04; OR, 1.59; 95% CI, 1.02-2.46) (Table 1).