Association between fibromyalgia syndrome and polymorphism of the IL-4 gene in a Turkish population

Purpose: Fibromyalgia (FM) syndrome is a form of non-articular rheumatism characterized by long term and widespread musculoskeletal pain, morning stiffness, sleep disturbance, paresthesia, and pressure hyperalgesia at characteristic sites, called soft tissue tender points. The etiology of FM is still obscure. Genetic factors may predispose individuals to FM. Cytokines may play a role in the pathophysiology of FM. The aim of this study was to investigate the interleukin-4 (IL-4) 70 bp VNTR variations in Turkish patients with FM and evaluate if there was an association with clinical features, especially between these polymorphisms. Methods: The study included 300 patients with FM and 270 healthy controls. Genomic DNA was isolated and genotyped using polymerase chain reaction (PCR) for the IL-4 gene 70 bp VNTR polymorphisms. Results: There was statistically significant difference between the groups with respect to IL-4 genotype distribution and allele frequencies (p < 0.0001). The homozygous P1P1 genotype and P-1 allele were significantly higher in FM patients than in healthy controls (p = 0.04; OR: 325, 95% CI: 1-10, p < 0.0001; OR:4.84, 95% CI:3-7.7). There was not any difference between the groups respect to IL-4 genotype distribution and allele frequencies (p > 0.05) and clinical characteristics. Conclusion: Our findings suggest that there is an association of IL-4 gene 70 bp VNTR polymorphism with susceptibility of a person for development of FM. As a result, further studies are necessary to determine whether IL-4 may be a genetic marker for FM in the Turkish population. (C) 2013 Elsevier B.V. All rights reserved.