Abstract
BACKGROUND: The recurrence rate of Henoch-Schönlein purpura (HSP) is 2.7%-30%, with varied average intervals between the first and second episodes. Few studies have explored the incidence and risk factors for recurrent HSP. METHODS: We used a 16-year nationwide database to analyze the incidence of recurrent HSP. Patients with HSP were identified, and risk factors for recurrent HSP were explored. Kaplan-Meier and Cox regression model analyses were performed, and covariates were adjusted in the multivariate model. RESULTS: From January 1, 1997 to December 31, 2012, among 2,886,836 individuals in the National Health Insurance Research Database, 1002 HSP patients aged < 18 years were identified. Among them, 164 had ≥2 HSP episodes (recurrence rate, 16.4%; incidence of recurrent HSP, 7.05 per 100 person-years); 83.6% patients with one HSP episode remained free of secondary HSP. The average time intervals between the first and second and second and third HSP episodes were 9.2 and 6.4 months, respectively. After adjusting for demographic parameters, comorbidities, and socioeconomic status, recurrent HSP was found to occur more frequently in patients who had renal involvement (adjusted hazard ratio, 2.41; 95% confidence interval [CI], 1.64-3.54; p < 0.001), were receiving steroid therapy for > 10 days (adjusted hazard ratio, 8.13; 95%CI, 2.51-26.36; p < 0.001), and had allergic rhinitis (adjusted hazard ratio, 1.63; 95%CI, 1.06-2.50; p = 0.026). CONCLUSIONS: The annual incidence of recurrent HSP was low. However, children who had underlying allergic rhinitis, presented with renal involvement, and received steroid treatment for > 10 days should be notified regarding the possibility of recurrence.