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Objective: This cross-sectional study was designed to assess the clinical significance of the serum KL-6 in the diagnosis of interstitial lung disease (ILD) in patients with idiopathic inflammatory myopathy (IIM)., Methods: We measured serum KL-6 levels in 184 patients with IIM using a chemiluminescent enzyme immunoassay and compared KL-6 levels between patients with and without ILD, according to other clinical features., Results: IIM patients with ILD had significantly higher serum KL-6 levels than those without ILD (776.5 [372.3-1378.8] vs. 297.5 [204.75-599.3] U/ml, P < 0.001). At a cut-off of 461.5 U/ml identified by ROC curve, serum KL-6 yielded a sensitivity of 70.2% and specificity of 73.9% for ILD in IIM patients. IIM patients with an elevated serum KL-6 were more likely to have clinical symptoms of mechanic's hands (P = 0.002), anti-Jo-1 antibody positivity (P = 0.021), dysphagia (P = 0.039), hoarseness (P < 0.001), and polyarthritis/polyarthralgia (P < 0.001). Significant inverse correlations were found between serum KL-6 levels and pulmonary function tests (P < 0.01), including forced vital capacity (FVC, %Pred), total lung capacity (TLC, %Pred), and diffusing capacity for carbon monoxide (DLCO, %Pred)., Conclusions: Serum KL-6 offers high sensitivity and specificity for the diagnosis of IIM-associated ILD and is inversely correlated with pulmonary function deterioration. Serum KL-6 may represent a promising biomarker for monitoring ILD severity in IIM patients.

Objectives: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the TNF super-family, which is involved in the regulation of immune response and pathogenesis of autoimmune diseases, including polymyositis (PM) and dermatomyositis (DM). In this study, we examined the level and origin of serum-soluble TRAIL (sTRAIL) in patients with PM and DM and analyzed its association with disease activity and clinical features., Method: 11 PM patients, 33 DM patients, and 20 healthy controls were enrolled in this study. Clinical features were recorded when admitted, and disease activity was evaluated by myositis disease activity assessment visual analogue scale (MYOACT). TRAIL expression in muscle tissues was detected by immunohistochemistry. Serum sTRAIL levels were measured by enzyme-linked immunosorbent assay. The expression of membrane TRAIL (mTRAIL) and its receptors, including DR4 and DR5, on circulating T cells was analyzed by flow cytometry., Results: TRAIL was expressed in infiltrated inflammatory cells in muscle tissues from patients. The serum sTRAIL level was markedly increased in patients and was positively correlated with the disease activity. Serum sTRAIL was decreased after therapy in patients and was specifically higher in patients with dysphagia, but lower in patients with autoantibody Jo-1 positive. The frequency of mTRAIL and its receptors on circulating T cells from patients were significantly elevated than that from healthy controls., Conclusions: The serum sTRAIL could be a biomarker for evaluating the disease activity of PM and DM, and targeting the generation of TRAIL in T cells might be a potential approach in the treatment of PM and DM.

Background: Little is known so far on the lipid profile in polymyositis (PM) patients. Our aim is to identify lipid profiles in untreated patients with early PM, to assess the association between lipid profiles and C-reactive protein (a sensitive marker of inflammation) in these patients., Methods and Findings: This work was conducted as a case-control study. Sixty untreated patients with PM and 60 age- and sex-matched healthy controls were included. The duration of PM was less than six months, and none of them had received intermittent or regular corticosteroids or disease-modifying antirheumatic drugs or biological agents prior to the study. Triglyceride (TG), total cholesterol (TC), LDL-cholesterol (LDL-C), and HDL-cholesterol (HDL-C), and C-reactive protein (CRP) were assessed using standard techniques. Thirty patients (50%) had a decreased level of HDL-C and 47% had an increased level of TG. The levels of HDL-C, LDL-C, and TC in PM were significantly lower than in controls (P<0.001, P<0.01, P<0.001, respectively). The level of TG was significantly higher in PM than in controls (P<0.001). The level of very low LDL-cholesterol (VLDL-C), and the ratios of VLDL-C/LDL-C, TC/HDL-C, and LDL-C/HDL-C were significantly higher than in controls (all P<0.001). Serum CRP levels correlated negatively with HDL-C (r = -0.352, P = 0.006) and TC (r = -0.262, P = 0.043). After adjustment for age, gender, smoking, drinking, body mass index, and pulmonary fibrosis/infection, linear regression model demonstrated that CRP is associated with HDL-C among PM patients (P = 0.028)., Conclusions: Dyslipidemia is a common feature in patients with PM that is characterized by a decrease in HDL-C and an increase in TG, suggesting a high risk of atherosclerosis. The Inflammatory condition in PM may account for the metabolism of HDL-C.