To investigate whether polymorphisms in the interleukin (IL)-1 locus (human chrom. 2q13) and TNF-alpha gene are associated with susceptibility to or severity of polymyalgia rheumatica (PMR).
The study included 92 consecutive PMR patients diagnosed over a 5-year period who were prospectively followed-up for at least one year and 79 healthy controls over the age of 50 residing in the same area. All the patients and controls were Caucasians of Italian origin. We tested the allelic distribution of IL-1A (+4845), IL-B (-511), IL-B (+3954), IL-1RN Intron 2 VNTR and TNFA (-308). Frequencies were compared in the patient and control groups.
A statistically significant association between PMR patients and the IL1RN*2 allele in the homozygous state was found [OR 8.46 (95% CI 1.05-68.31)]. The polymorphisms in the other genes of the IL-1 gene cluster did not reveal any association with PMR when compared with controls. A weak association between PMR patients and the TNF2 allele was also present [OR 2.09 (95% CI 1.0-4.17)]. None of the gene variants studied was associated with the disease severity of PMR.
Our findings show that IL1RN*2 allele, particularly in the homozygous state, is associated with susceptibility to, but not with the severity of, PMR.