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The 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 effect of its receptor inhibitor—tocilizumab—has been recently studied. The 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). The 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.

No abstract

Deficiency in some complement factors is known to cause both systemic lupus erythematosus (SLE) and dermatomyositis (DM). Mannose-binding lectin (MBL) is a recognition molecule of the lectin pathway, and its low levels are reported to influence some autoimmune diseases. Furthermore, MBL2 polymorphisms have been described associated with low MBL serum levels due to impaired MBL structure and function. This is a pilot study to investigate the role of MBL2-550G/C (H/L), -221G/C (Y/X), Arg52Cys (D), Gly54Asp (B), Gly57Glu (C) polymorphisms and MBL serum levels as a risk factor for a development of adult DM and SLE in Bulgarian patients. None of the studied MBL2 polymorphisms appeared associated with the diseases investigated. However, we have found an increased OR of MBL2-221XY genotype in the patients with SLE (OR 1.64, 95%CI 0.77-3.52). MBL2 polymorphisms seemed to affect MBL serum levels and to be associated with the clinical features although none of the associations remained statistically significant after Bonferroni correction. The-550L allele showed an association with electromyography findings in patients with DM. The-221XY genotype was associated with photosensitivity in patients with SLE. The 54AB genotype showed an association with malar rash in patients with SLE, but it appeared decreased among SLE patients with ANA. In conclusion, our results suggest that the MBL2 polymorphisms have rather a disease modifying role and they are not associated with the disease susceptibility in adult DM and SLE among Bulgarian patients.

The TNF-α polymorphisms are associated with increased relative risk mainly for SLE, particularly in women, while their role for DM is less evident and needs further analysis in an enlarged sample cohort.

Polymorphisms in the cytokine genes and their natural antagonists are thought to influence the predisposition to dermatomyositis (DM) and systemic lupus erythematosus (SLE). A variable number tandem repeat (VNTR) polymorphism of 86 bp in intron 2 of the interleukin-1 receptor antagonist (IL-1RN) gene leads to the existence of five different alleles which cause differences in the production of both IL-1RA (interleukin-1 receptor antagonist) and IL-1β. The aim of this case-control study was to investigate the association between the IL-1RN VNTR polymorphism and the susceptibility to DM and SLE in Bulgarian patients. Altogether 91 patients, 55 with SLE and 36 with DM, as well as 112 unrelated healthy controls, were included in this study. Only three alleles were identified in both patients and controls ((1) four repeats, (2) two repeats, and (3) five repeats). The IL-1RN*2 allele (P = 0.02, OR 2.5, and 95% CI 1.2–5.4) and the 1/2+2/2 genotypes were found prevalent among the SLE patients (P = 0.05, OR 2.6, and 95% CI 1–6.3). No association was found between this polymorphism and the ACR criteria for SLE as well as with the susceptibility to DM. Our results indicate that the IL-1RN VNTR polymorphism might play a role in the susceptibility of SLE but not DM.

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Citation: Dourmishev LA, Hristova MH, Kamenarska ZG, Savov AS, Vinkov AI, Kaneva R, Mitev V. Genetically determined TNF-α secretion infl uences the development of dermatomyositis and systemic lupus erythematosus. Folia Med (Plovdiv) 2018;60(2):216-20.