IgAV can occur in patients of any age; however, it occurs predominantly between the ages of 2 and 10 years. Peak incidence is between 4 and 7 years.[11]Leung AKC, Barankin B, Leong KF. Henoch-Schönlein purpura in children: an updated review. Curr Pediatr Rev. 2020;16(4):265-76.
http://www.ncbi.nlm.nih.gov/pubmed/32384035?tool=bestpractice.com
In North America, the annual incidence of IgAV in children is around 13.5 cases per 100,000 population.[1]Roberts PF, Waller TA, Brinker TM, et al. Henoch-Schonlein purpura: a review article. South Med J. 2007 Aug;100(8):821-4.
http://www.ncbi.nlm.nih.gov/pubmed/17713309?tool=bestpractice.com
[12]Gedalia A. Henoch-Schonlein purpura. Curr Rheumatol Rep. 2004 Jun;6(3):195-202.
http://www.ncbi.nlm.nih.gov/pubmed/15134598?tool=bestpractice.com
In the UK, routinely collected primary care data indicate that the incidence of childhood-onset IgAV is 27.22 per 100,000 person-years.[13]Tracy A, Subramanian A, Adderley NJ, et al. Cardiovascular, thromboembolic and renal outcomes in IgA vasculitis (Henoch-Schönlein purpura): a retrospective cohort study using routinely collected primary care data. Ann Rheum Dis. 2019 Feb;78(2):261-9.
https://www.doi.org/10.1136/annrheumdis-2018-214142
http://www.ncbi.nlm.nih.gov/pubmed/30487151?tool=bestpractice.com
People of white and Asian ethnicity have the highest incidence, and people of black ethnicity the lowest.[1]Roberts PF, Waller TA, Brinker TM, et al. Henoch-Schonlein purpura: a review article. South Med J. 2007 Aug;100(8):821-4.
http://www.ncbi.nlm.nih.gov/pubmed/17713309?tool=bestpractice.com
[12]Gedalia A. Henoch-Schonlein purpura. Curr Rheumatol Rep. 2004 Jun;6(3):195-202.
http://www.ncbi.nlm.nih.gov/pubmed/15134598?tool=bestpractice.com
Males are slightly more often affected than females by a ratio of up to 2:1.[12]Gedalia A. Henoch-Schonlein purpura. Curr Rheumatol Rep. 2004 Jun;6(3):195-202.
http://www.ncbi.nlm.nih.gov/pubmed/15134598?tool=bestpractice.com
IgAV can follow an upper respiratory tract infection, and as a result occurs most frequently in the autumn, winter, and early spring.[14]Calvino MC, Llorca J, Garcia-Porrua C, et al. Henoch-Schonlein purpura in children from northwestern Spain: a 20-year epidemiologic and clinical study. Medicine (Baltimore). 2001 Sep;80(5):279-90.
http://www.ncbi.nlm.nih.gov/pubmed/11552081?tool=bestpractice.com
[15]Hwang HH, Lim IS, Choi BS, et al. Analysis of seasonal tendencies in pediatric Henoch-Schönlein purpura and comparison with outbreak of infectious diseases. Medicine (Baltimore). 2018 Sep;97(36):e12217.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6133644
http://www.ncbi.nlm.nih.gov/pubmed/30200139?tool=bestpractice.com
During childhood, as onset age increases, patients have arthralgia/arthritis less frequently, but are more prone to renal involvement.[16]Liao CH, Tsai M, Yang YH, et al. Onset age is a risk factor for refractory pediatric IgA vasculitis: a retrospective cohort study. Pediatr Rheumatol Online J. 2020 Nov 10;18(1):86.
https://www.doi.org/10.1186/s12969-020-00480-3
http://www.ncbi.nlm.nih.gov/pubmed/33172497?tool=bestpractice.com