大多数研究将特发性炎症性肌病 (idiopathic inflammatory myopathies, IIM) 的发病率与皮肌炎 (DM) 和多发性肌炎 (PM) 合在一起,但不包括临床无肌病性皮肌炎患者。在美国,成人特发性炎症性肌病的年发病率为每 100 万人 5.5 至 8.9 例。[5]Medsger TA, Dawson WN Jr, Masi AT. The epidemiology of polymyositis. Am J Med. 1970;48:715-723.http://www.ncbi.nlm.nih.gov/pubmed/5420557?tool=bestpractice.com[6]Kurland LT, Hauser WA, Ferguson RH, et al. Epidemiologic features of diffuse connective tissue disorders in Rochester, Minn., 1951 through 1967, with special reference to systemic lupus erythematosus. Mayo Clin Proc. 1969;44:649-663.http://www.ncbi.nlm.nih.gov/pubmed/4390370?tool=bestpractice.com[7]Oddis CV, Conte CG, Steen VD, et al. Incidence of polymyositis-dermatomyositis: a 20-year study of hospital diagnosed cases in Allegheny County, PA 1963-1982. J Rheumatol. 1990;17:1329-1334.http://www.ncbi.nlm.nih.gov/pubmed/2254890?tool=bestpractice.com随着时间延长发病率有逐渐升高的趋势,但这可能反映的是诊断率和报告率提高,而不是真正的发病率升高。[5]Medsger TA, Dawson WN Jr, Masi AT. The epidemiology of polymyositis. Am J Med. 1970;48:715-723.http://www.ncbi.nlm.nih.gov/pubmed/5420557?tool=bestpractice.com[6]Kurland LT, Hauser WA, Ferguson RH, et al. Epidemiologic features of diffuse connective tissue disorders in Rochester, Minn., 1951 through 1967, with special reference to systemic lupus erythematosus. Mayo Clin Proc. 1969;44:649-663.http://www.ncbi.nlm.nih.gov/pubmed/4390370?tool=bestpractice.com[7]Oddis CV, Conte CG, Steen VD, et al. Incidence of polymyositis-dermatomyositis: a 20-year study of hospital diagnosed cases in Allegheny County, PA 1963-1982. J Rheumatol. 1990;17:1329-1334.http://www.ncbi.nlm.nih.gov/pubmed/2254890?tool=bestpractice.com在西班牙,皮肌炎的年发病率是每 100 万人 4.9 例。[8]Vargas-Leguas H, Selva-O'Callaghan A, Campins-Marti M, et al. Polymyositis-dermatomyositis: incidence in Spain (1997-2004). Medicina Clinica. 2007;129:721-724. [In Spanish]http://www.ncbi.nlm.nih.gov/pubmed/18053482?tool=bestpractice.com
成年型皮肌炎中女性发病率更高,与男性发病率之比为 2:1。发病高峰年龄为 40-60 岁,其中 40-50 岁最为常见。[9]Klippel JH, Dieppe PA. Rheumatology. 2nd ed. London, UK: Mosby; 1997.如果皮肌炎伴有其他结缔组织病,则女男比例升高为 10:1。黑种人的发生率是白种人的 3 倍。[9]Klippel JH, Dieppe PA. Rheumatology. 2nd ed. London, UK: Mosby; 1997.恶性肿瘤相关的皮肌炎男女发生率相近,发病年龄略大。[10]Caro I. Dermatomyostis. Semin Cutan Med Surg. 2001;20:38-45.http://www.ncbi.nlm.nih.gov/pubmed/11308135?tool=bestpractice.com[11]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
青少年型皮肌炎的年发病率为每 100 万人 2-3 例。[12]Ramanan AV, Feldman BM. Clinical outcomes in juvenile dermatomyositis. Curr Opin Rheumatol. 2002;14:658-662.http://www.ncbi.nlm.nih.gov/pubmed/12410087?tool=bestpractice.com女孩更常受累 (2.3:1),平均发病年龄为 10 岁。[9]Klippel JH, Dieppe PA. Rheumatology. 2nd ed. London, UK: Mosby; 1997.[13]Mendez E, Lipton R, Dyer A, et al. The incidence of juvenile dermatomyositis (JDM): results from the NIAMS JDM research registry. Arthritis Rheum. 1999;42:S300.