Association between allergic diseases and risks of HSP and HSP nephritis: a population-based study

Background: Some allergic inflammation-associated mediators have been reported in acute stage of Henoch-Schonlein purpura (HSP). However, the association of children with allergic diseases and their subsequent risks of HSP and HSP nephritis remain unknown. Methods: In this study, we included 2,240 children with HSP diagnosed between 2000 and 2008 as well as 8,960 non-HSP controls matched for age, sex, and level of urbanization. The odds ratios (ORs) of HSP were calculated with respect to associations with pre-existing allergic diseases. Results: Children with allergic diseases had an increased subsequent risk of HSP; the lowest adjusted OR (aOR) was 1.33 for allergic conjunctivitis (95% confidence interval (CI): 1.17-1.52) and the highest was 1.68 for asthma (95% CI: 1.48-1.91). The aOR increased to 2.03 (95% CI: 1.80-2.31) in children with at least two allergic diseases. Children who visited medical institutes more often per year for associated allergic diseases had an increased risk of HSP. Of the 2,240 children with HSP, 249 (11%) had HSP nephritis and 45.8% of those with nephritis had history of any allergic disease. Conclusion: Atopic children had an increased subsequent risk of HSP but not an increased risk of HSP nephritis.