DM is a rare disease that can occur at any age. Evidence suggests that there are two peaks of incidence: between 5 and 15 years of age and between 40 and 60 years.[5]Bendewald MJ, Wetter DA, Li X, et al. Incidence of dermatomyositis and clinically amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch Dermatol. 2010 Jan;146(1):26-30.
https://jamanetwork.com/journals/jamadermatology/fullarticle/420951
http://www.ncbi.nlm.nih.gov/pubmed/20083689?tool=bestpractice.com
[6]Gerami P, Walling HW, Lewis J, et al. A systematic review of juvenile-onset clinically amyopathic dermatomyositis. Br J Dermatol. 2007 Oct;157(4):637-44.
http://www.ncbi.nlm.nih.gov/pubmed/17596148?tool=bestpractice.com
[7]Gaubitz M. Epidemiology of connective tissue disorders. Rheumatology (Oxford). 2006 Oct;45 (suppl 3):iii3-4.
https://academic.oup.com/rheumatology/article/45/suppl_3/iii3/2255626
http://www.ncbi.nlm.nih.gov/pubmed/16987829?tool=bestpractice.com
Adult-onset DM has a female preponderance of approximately 2.5:1.[7]Gaubitz M. Epidemiology of connective tissue disorders. Rheumatology (Oxford). 2006 Oct;45 (suppl 3):iii3-4.
https://academic.oup.com/rheumatology/article/45/suppl_3/iii3/2255626
http://www.ncbi.nlm.nih.gov/pubmed/16987829?tool=bestpractice.com
[8]Smoyer-Tomic KE, Amato AA, Fernandes AW. Incidence and prevalence of idiopathic inflammatory myopathies among commercially insured, Medicare supplemental insured, and Medicaid enrolled populations: an administrative claims analysis. BMC Musculoskelet Disord. 2012 Jun 15;13:103.
https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-13-103
http://www.ncbi.nlm.nih.gov/pubmed/22703603?tool=bestpractice.com
DM is more common in the black population than in the white population.[7]Gaubitz M. Epidemiology of connective tissue disorders. Rheumatology (Oxford). 2006 Oct;45 (suppl 3):iii3-4.
https://academic.oup.com/rheumatology/article/45/suppl_3/iii3/2255626
http://www.ncbi.nlm.nih.gov/pubmed/16987829?tool=bestpractice.com
[8]Smoyer-Tomic KE, Amato AA, Fernandes AW. Incidence and prevalence of idiopathic inflammatory myopathies among commercially insured, Medicare supplemental insured, and Medicaid enrolled populations: an administrative claims analysis. BMC Musculoskelet Disord. 2012 Jun 15;13:103.
https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-13-103
http://www.ncbi.nlm.nih.gov/pubmed/22703603?tool=bestpractice.com
Malignancy-associated DM occurs with similar frequency in both sexes and is more common in people over 50 years of age with the risk increasing with age.[7]Gaubitz M. Epidemiology of connective tissue disorders. Rheumatology (Oxford). 2006 Oct;45 (suppl 3):iii3-4.
https://academic.oup.com/rheumatology/article/45/suppl_3/iii3/2255626
http://www.ncbi.nlm.nih.gov/pubmed/16987829?tool=bestpractice.com
[9]Caro I. Dermatomyostis. Semin Cutan Med Surg. 2001 Mar;20(1):38-45.
http://www.ncbi.nlm.nih.gov/pubmed/11308135?tool=bestpractice.com
[10]Marie I, Hatron PY, Levesque H, et al. Influence of age on characteristics of polymyositis and dermatomyositis in adults. Medicine (Baltimore). 1999 May;78(3):139-47.
https://journals.lww.com/md-journal/Citation/1999/05000/Influence_of_Age_on_Characteristics_of.1.aspx
http://www.ncbi.nlm.nih.gov/pubmed/10352646?tool=bestpractice.com
A US population-based study reported an estimated annual incidence of all subtypes of DM of 9.63 per million people, 13.98 per million for women and 4.68 per million for men.[5]Bendewald MJ, Wetter DA, Li X, et al. Incidence of dermatomyositis and clinically amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch Dermatol. 2010 Jan;146(1):26-30.
https://jamanetwork.com/journals/jamadermatology/fullarticle/420951
http://www.ncbi.nlm.nih.gov/pubmed/20083689?tool=bestpractice.com
The estimated annual incidence for the clinically amyopathic subtype of DM was 2.08 per million people, 3.50 per million for women and 0.45 per million for men.[5]Bendewald MJ, Wetter DA, Li X, et al. Incidence of dermatomyositis and clinically amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch Dermatol. 2010 Jan;146(1):26-30.
https://jamanetwork.com/journals/jamadermatology/fullarticle/420951
http://www.ncbi.nlm.nih.gov/pubmed/20083689?tool=bestpractice.com
The overall prevalence of all subtypes of DM was estimated at 21.42 per 100,000 people, 33.08 per 100,000 for women and 8.35 per 100,000 for men.[5]Bendewald MJ, Wetter DA, Li X, et al. Incidence of dermatomyositis and clinically amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch Dermatol. 2010 Jan;146(1):26-30.
https://jamanetwork.com/journals/jamadermatology/fullarticle/420951
http://www.ncbi.nlm.nih.gov/pubmed/20083689?tool=bestpractice.com
Juvenile-onset DM has an annual incidence of 2 to 3 cases per million.[11]Ramanan AV, Feldman BM. Clinical outcomes in juvenile dermatomyositis. Curr Opin Rheumatol. 2002 Nov;14(6):658-62.
http://www.ncbi.nlm.nih.gov/pubmed/12410087?tool=bestpractice.com
Girls are more commonly affected with the mean age of onset of around 10 years.[6]Gerami P, Walling HW, Lewis J, et al. A systematic review of juvenile-onset clinically amyopathic dermatomyositis. Br J Dermatol. 2007 Oct;157(4):637-44.
http://www.ncbi.nlm.nih.gov/pubmed/17596148?tool=bestpractice.com
[12]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.