Incidence of the Stevens-Johnson syndrome spectrum and its patterns in urban China.

Stevens-Johnson syndrome (SJS) spectrum is a series of rare, but life-threatening mucocutaneous hypersensitivity reactions. However, the epidemiological evidence of it is limited, especially in developing countries. The shape associations with age and its seasonal pattern are still uncertain. Therefore, this study aimed to describe the nationwide incidence of SJS spectrum, its associations with age and season, and its subsequent diagnosed diseases across urban China. By using national health insurance datasets from 2013 to 2017, this retrospective cohort study estimated the incidence of SJS spectrum and its associations in 23 Chinese provinces. SJS spectrum was defined to include SJS and/or toxic epidermal necrolysis (ICD-10 code: L51.1-2). First, age-specific incidence rates were estimated in each province and then pooled using a random-effects model. Relative risks (RR) of SJS spectrum in different seasons were estimated by Poisson regression. Diseases diagnosed within 6 months following SJS occurrence were described. In total, 9308 patients were identified (50.17% women, median age 45). The average standardized incidence rate of SJS spectrum was 3.43 (95% confidence interval [CI] 3.04-3.84) per million person-years, which increased by 0.57 (95% CI 0.29-0.84) per million person-years. Incidence rates were significantly higher among children age <10 years (5.48, 95% CI 4.02-7.09, p = 0.0036) and adults age ≥ 40 (5.50, 95% CI 4.35-6.78, p = 0.00085) than the group aged 10-40 years (3.12, 95% CI 2.29-4.07). The risk of SJS spectrum was highest in summer (vs autumn: RR = 1.83, 95% CI 1.72-1.93). The most frequently diagnosed disease within 6 months after the onset of SJS was respiratory disease (43.8%). In conclusion, this study provides evidence on the epidemiology of SJS spectrum in developing countries and supports the two-peak distribution of its incidence across age. Its high occurrence in summer needs further confirmation.