Intercellular adhesion molecule 1 (ICAM-1) is widely distributed in shoulder synovial membrane of active polymyalgia rheumatica (PMR) and strongly expressed in granulomatous inflammatory infiltrate of the temporal artery in giant cell arteritis (GCA). ICAM-1 genes may contribute to the inflammatory PMR/GCA processes. We examined potential associations of ICAM-1 gene polymorphisms with PMR/GCA susceptibility and severity.
We enrolled 121 consecutive patients with "pure" PMR and 56 patients with biopsy positive GCA residing in Reggio Emilia, Italy. Among patients with PMR, 91 had a followup duration of at least one year. Selected as control subjects were 228 healthy blood donors, 75 patients with nonarteritic central retinal artery occlusion, and 116 cataract surgery patients from the same geographic area. All PMR/GCA patients and controls were genotyped by polymerase chain reaction and allele-specific oligonucleotide techniques for ICAM-1 polymorphism at codon 241 (exon 4) and codon 469 (exon 6).
The frequency of R241 was significantly higher in PMR/GCA patients [p = 0.00001, odds ratio (OR) 5.0 (95% confidence intervals, CI 2.6-9.6) ], in pure PMR patients [p = 0.00001, OR 5.0 (95% CI 2.5-10.0)], and in GCA patients [p = 0.00005; OR 5.0 (95% CI 2.2-11.5)] compared to the healthy controls. The frequency of R241 was significantly higher in total PMR/GCA patients compared to patients with nonarteritic central retinal artery occlusion [p = 0.0007; OR 5.3 (95% CI 1.8-15.5)] and cataract surgery patients [p = 0.0003; OR 4.1 (95% CI 1.8-9.0)]. The distribution of E/K 469 genotype was similar in PMR/GCA patients and in the 3 control groups. Cox proportional hazards modeling identified 2 variables that independently increased the risk of PMR relapse/recurrence: erythrocyte sedimentation rate at diagnosis > 72 mm/h [relative risk 1.6 (95% CI 1.1-2.3)] and the presence of R241 allele [relative risk 1.6 (95% CI 1.1-2.4)].
Our findings show that G/R 241 polymorphism of ICAM-1 is associated with PMR/GCA susceptibility and confers an increased risk of relapse/recurrence in PMR.