Hindawi Publishing Corporation BioMed Research International Volume 2013, Article ID 315365, 5 pages http://dx.doi.org/10.1155/2013/315365 Research Article Role of the Promoter Polymorphism IL-6 -174G/C in Dermatomyositis and Systemic Lupus Erythematosus Maria Hristova, 1 Lyubomir Dourmishev, 2 Zornitsa Kamenarska, 3,4 Svetla Nikolova, 3,4 Radka Kaneva, 3,4 Anton Vinkov, 5 Marta Baleva, 1 Daniela Monova, 6 and Vanio Mitev 3,4 1 Department of Clinical Laboratory and Clinical Immunology, Medical University-Soia, 1 Georgi Soijski Street, 1431 Soia, Bulgaria 2 Department of Dermatology and Venereology, Medical University-Soia, 1 Georgi Soijski Street, 1431 Soia, Bulgaria 3 Molecular Medicine Center, Medical University-Soia, 2 Zdrave Street, 1431 Soia, Bulgaria 4 Department of Medical Chemistry and Biochemistry, Medical University-Soia, 2 Zdrave Street, 1431 Soia, Bulgaria 5 28 Diagnostic and Consultative Center-Soia, 1 Iliya Beshkov Street, 1592 Soia, Bulgaria 6 Department of Nephrology, Ministry of Interior Hospital, 79 Skobelev Boulevard, 1606 Soia, Bulgaria Correspondence should be addressed to Zornitsa Kamenarska; kamenarska@yahoo.com Received 29 April 2013; Revised 29 July 2013; Accepted 12 August 2013 Academic Editor: Tomoshige Kino Copyright © 2013 Maria Hristova et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he promoter polymorphism −174G/C within the interleukin-6 gene (IL-6) has been reported to have a functional importance through the modulation of IL-6 gene expression in vitro and in vivo. IL-6 is thought to play an important role in autoimmune diseases and the efect of its receptor inhibitor—tocilizumab—has been recently studied. he aim of this case-control study was to investigate the association between the interleukin-6 −174G/C single nucleotide polymorphism and the susceptibility to dermatomyositis (DM) and systemic lupus erythematosus (SLE) in Bulgarian patients. Altogether, 87 patients—52 with SLE and 35 with DM—as well as 80 unrelated healthy controls were included in this study. All of them were analyzed by restriction fragment length polymorphism analysis (RFLP). he GG genotype and the G allele appeared to be associated with SLE, especially in women. None of the genotypes showed an association with DM. However, the G allele appeared to be associated with muscle weakness and it is a risk factor for elevated muscle enzymes. Our results indicate that IL-6 −174G/C polymorphism might be associated with the susceptibility to SLE especially in women. Although it is not associated with DM, it seems that IL-6 −174G/C polymorphism could modulate some clinical features in the autoimmune myopathies. 1. Introduction Dermatomyositis (DM) and systemic lupus erythematosus (SLE) are diseases of unknown etiology. However, the dys- regulation of cytokine production or action is thought to have an important role in their development [1]. he cytokine secretion was found to be under genetic control [2]. In our previous study, we have found association between TNF- polymorphisms and the etiology of DM and SLE in Bulgarian patients [3]. TNF- and IL-1 can induce IL-6 and IL-6 induces B-cell diferentiation to plasma cells, hyperactivity, and secretion of antibodies and also promotes T-cell proliferation, cytotoxic T-cell diferentiation, and local inlammation. According to Linker-Israeli et al. [4], elevated plasma levels of IL-6 messenger-RNA and protein could be detected in SLE patients. Serum TNF- and IL-6 levels were reported to be sensitive markers for SLE activity [5, 6]. IL-6 is also consid- ered to play a role in the development of DM, since it leads to reduced myogenesis [7]. Hagiwara et al. [8] have found that patients with DM and polymyositis have an increased number of IL-6 secreting cells compared to controls. Bilgic et al. [9] suggest that IL-6 serum level is a candidate biomarker for disease activity in both adult and juvenile DM. he G allele of the IL-6 −174G/C polymorphism is asso- ciated with higher IL-6 expression [10]. he presence of the G allele has been associated with poor outcome in a variety of diseases including coronary artery disease [11], more severe