CD8A and juvenile dermatomyositis: Edema (P < 0.0001), skin ulcers (P = 0.0003), severe muscle weakness (dysphagia/hoarseness/soft voice, P = 0.0089; muscle strength<= grade 3, P = 0.0041), CD4 / CD8 ratio < 1.4 (P = 0.0255) and ferritin > 200 ng / ml (P = 0.0361) were considerably associated with refractory JDM.