Comparison of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and Fn14 mRNA levels of polymyositis (PM)/dermatomyositis (DM) and of healthy controls. Total RNA was isolated from fresh-frozen muscle tissue using TRIzol reagent, and fluorescent quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed. The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was used as an internal control. 2−Δ CT was used to compute the expression values of the target genes. (A) TWEAK mRNA levels in muscle tissue of PM, DM and healthy controls. (B) Fn14 mRNA levels in muscle tissue of PM, DM and healthy controls. (C) Fn14 mRNA levels were compared in PM/DM patients sub-grouped based on the presence of oropharyngeal dysphagia. (D) Correlation of Fn14 mRNA levels with myositis disease activity assessment visual analog scales (MYOACT) muscle disease activity scores. (E) Correlation of Fn14 mRNA levels with MYOACT global disease activity scores. The data of unpaired samples were analyzed by using the Mann-Whitney U-test. Spearman’s correlation analysis was used to test for correlations. Horizontal bars indicate median levels.