Editing Systemic scleroderma (section)

== Epidemiology ==
Systemic scleroderma is a [[rare disease]], with an annual incidence that varies in different populations. Estimates of incidence (new cases per million people) range from 3.7 to 43 in the United Kingdom and Europe, 7.2 in Japan, 10.9 in Taiwan, 12.0 to 22.8 in Australia, 13.9 to 21.0 in the United States, and 21.2 in Buenos Aires.<ref name=Barnes>{{cite journal |last1=Barnes |first1=Jammie |last2=Mayes |first2=Maureen D. |title=Epidemiology of systemic sclerosis |journal=Current Opinion in Rheumatology |date=March 2012 |volume=24 |issue=2 |pages=165–170 |doi=10.1097/BOR.0b013e32834ff2e8|pmid=22269658 |s2cid=24050211 }}</ref> The interval of peak onset starts at age 30<ref name=uptodate>[https://www.uptodate.com/contents/systemic-sclerosis-scleroderma-and-pregnancy Systemic sclerosis (scleroderma) and pregnancy] By Bonnie L Bermas, MD. Retrieved on Dec 13, 2009</ref> and ends at age 50.<ref name=uptodate/>

Globally, estimates of prevalence vary from 31.0 to 658.6 affected people per million.<ref name=Barnes/> Systemic sclerosis has a female:male ratio of 3:1 (8:1 in mid- to late childbearing years). Incidence is twice as high among African Americans. Full-blooded [[Choctaw|Choctaw Native Americans]] in Oklahoma have the highest prevalence in the world (469 per 100,000).<ref>{{Cite journal |last1=Arnett |first1=F. C. |last2=Howard |first2=R. F. |last3=Tan |first3=F. |last4=Moulds |first4=J. M. |last5=Bias |first5=W. B. |last6=Durban |first6=E. |last7=Cameron |first7=H. D. |last8=Paxton |first8=G. |last9=Hodge |first9=T. J. |last10=Weathers |first10=P. E. |last11=Reveille |first11=J. D. |date=August 1996 |title=Increased prevalence of systemic sclerosis in a Native American tribe in Oklahoma. Association with an Amerindian HLA haplotype |journal=Arthritis and Rheumatism |volume=39 |issue=8 |pages=1362–1370 |doi=10.1002/art.1780390814 |issn=0004-3591 |pmid=8702445|doi-access=free }}</ref>

The disease has some hereditary association. It may also be caused by an immune reaction to a virus ([[molecular mimicry]]) or by toxins.<ref name="Harrison's" />