Serum interleukin-6 level and its association with pulmonary involvement in progressive systemic sclerosis; a case-control study.

Background: Primary Systemic Sclerosis (PSS) is a connective tissue disorder characterized by excessive collagen deposition in the skin and internal organs. Interstitial lung disease (ILD) is a late demonstration of PSS and cytokines can contribute to the disease pathology. The purpose of the current study was to determine the association between serum interleukin-6 level and pulmonary involvement in progressive systemic sclerosis.

Methods and materials: Demographic data and serum interleukin-6 levels were measured for 30 PSS patients with pulmonary involvement (case group) and 30 PSS patients without pulmonary involvement (control group) following informed consent. The disease duration and activity, C-reactive protein (CRP), chest x-ray and highresolution CT scan (HRCT) findings, ejection fraction (EF) and echocardiography findings, and pulmonary artery pressure (PAP) were also determined in both groups.

Results: The age of patients in case and control groups was 52.5 ± 9.3 and 43.9 ± 9.7 years, respectively (p = 0.001). No significant difference was found between serum levels of IL-6 in case and control groups (73.1 ± 95.4 vs 46.7 ± 83.6 pg/ml, p = 0.267). However, IL-6 level was significantly higher in male case patients compared to male controls (p = 0.007). The duration of PSS was 11.6 ± 6.4 and 7.4 ± 4.2 years in case and control groups, respectively (p = 0.002). The quantitative CRP and PAP was also significantly higher in case patients (p = 0.01 and p < 0.001, respectively). There was found reticulonodular pattern in 20 (66.7%) of the cases, whereas 28 (93.3%) of the controls had normal Chest X-rays (CXR) (p < 0.001). EF was significantly lower in case patients compared to control patients (p = 0.001).

Conclusion: The serum level of IL-6 did not appear to have a relationship with pulmonary involvement, hence it could not be regarded as a potential therapeutic target.