使用泼尼松龙后，25% 患者症状完全缓解。[57]Joffe MM, Love LA, Leff RL, et al. Drug therapy of the idiopathic inflammatory myopathies: predictors of response to prednisone, azathioprine, and methotrexate and a comparison of their efficacy. Am J Med. 1993;94:379-387.http://www.ncbi.nlm.nih.gov/pubmed/8386437?tool=bestpractice.com
包涵体肌炎反应不佳，而有氨酰基-tRNA 合成酶或信号识别颗粒 (SRP) 抗体的患者通常对泼尼松龙有部分反应。[102]Oddis CV. Idiopathic inflammatory myopathy: management and prognosis. Rheum Dis Clin North Am. 2002;28:979-1001.http://www.ncbi.nlm.nih.gov/pubmed/12506780?tool=bestpractice.com对泼尼松龙的最初反应可能是对随后其他免疫抑制药剂反应的预测因子。[102]Oddis CV. Idiopathic inflammatory myopathy: management and prognosis. Rheum Dis Clin North Am. 2002;28:979-1001.http://www.ncbi.nlm.nih.gov/pubmed/12506780?tool=bestpractice.com
影响患者前景的因素
据报导，5 年和 10 年的存活率分别为 95% 和 84%。[102]Oddis CV. Idiopathic inflammatory myopathy: management and prognosis. Rheum Dis Clin North Am. 2002;28:979-1001.http://www.ncbi.nlm.nih.gov/pubmed/12506780?tool=bestpractice.com[103]Sultan SM, Ioannou Y, Moss K, et al. Outcome in patients with idiopathic inflammatory myositis: morbidity and mortality. Rheumatology (Oxford). 2002;41:22-26.http://rheumatology.oxfordjournals.org/cgi/content/full/41/1/22http://www.ncbi.nlm.nih.gov/pubmed/11792875?tool=bestpractice.com与存活率较低有关的因素包括老年、恶性肿瘤、皮质类固醇疗法启动延迟、咽部吞咽困难伴吸入性肺炎、间质性肺疾病 (ILD) 及心肌受累。[102]Oddis CV. Idiopathic inflammatory myopathy: management and prognosis. Rheum Dis Clin North Am. 2002;28:979-1001.http://www.ncbi.nlm.nih.gov/pubmed/12506780?tool=bestpractice.com[104]Torres C, Belmonte R, Carmona L, et al. Survival, mortality and causes of death in inflammatory myopathies. Autoimmunity. 2006;39:205-215.http://www.ncbi.nlm.nih.gov/pubmed/16769654?tool=bestpractice.com[105]Medsger TA Jr, Robinson H, Masi AT. Factors affecting survivorship in polymyositis. A life-table study of 124 patients. Arthritis Rheum. 1971;14:249-258.http://www.ncbi.nlm.nih.gov/pubmed/5549971?tool=bestpractice.com[106]Maugar YM, Berthelot JM, Abbas AA, et al. Long-term prognosis of 69 patients with dermatomyositis or polymyositis. Clin Exp Rheumatol. 1996;14:263-274.http://www.ncbi.nlm.nih.gov/pubmed/8809440?tool=bestpractice.com[107]Marie I, Hatron PY, Levesque H, et al. Influence of age on characteristics of polymyositis and dermatomyositis in adults. Medicine (Baltimore). 1999;78:139-147.http://www.ncbi.nlm.nih.gov/pubmed/10352646?tool=bestpractice.com[108]Marie I, Hachulla E, Hatron PY, et al. Polymyositis and dermatomyositis: short term and longterm outcome, and predictive factors of prognosis. J Rheumatol. 2001;28:2230-2237.http://www.ncbi.nlm.nih.gov/pubmed/11669162?tool=bestpractice.com[109]Danko K, Ponyi A, Constantin T, et al. Long-term survival of patients with idiopathic inflammatory myopathies according to clinical features: a longitudinal study of 162 cases. Medicine (Baltimore). 2004;83:35-42.http://www.ncbi.nlm.nih.gov/pubmed/14747766?tool=bestpractice.com
血清自身抗体中，抗 SRP是最差预后的标志；抗合成酶还与疾病反复发作和较低的生存率有关。
相反，有抗多发性肌炎 Scl 与抗 Mi-2 抗体的患者的 5 年生存率接近 95%。[102]Oddis CV. Idiopathic inflammatory myopathy: management and prognosis. Rheum Dis Clin North Am. 2002;28:979-1001.http://www.ncbi.nlm.nih.gov/pubmed/12506780?tool=bestpractice.com[110]Oddis CV, Okano Y, Rudert WA, et al. Serum autoantibody to the nucleolar antigen PM-Scl. Clinical and immunogenetic associations. Arthritis Rheum. 1992;35:1211-1217.http://www.ncbi.nlm.nih.gov/pubmed/1418007?tool=bestpractice.com
