Antibiotic Exposure, Infection, and the Development of Pediatric Psoriasis A Nested Case-Control Study

IMPORTANCE Antibiotics disrupt human microbiota and have been associated with several pediatric autoimmune diseases. Psoriasis activity has been linked to group A streptococcal and viral infections. OBJECTIVE To determine whether antibiotic exposure and infections are independently associated with incident psoriasis in children. DESIGN, SETTING, AND PARTICIPANTS This nested case-control study used data from the Health Improvement Network database, a population-representative electronic health records database from the United Kingdom, from June 27, 1994, through January 15, 2013. Data were analyzed from September 17, 2014, through August 12, 2015. Children aged 1 to 15 years with newly diagnosed psoriasis (n = 845) were compared with age-and sex-matched controls (n = 8450) randomly chosen at the time of psoriasis diagnosis from general practices with at least one case, excluding children with immunodeficiency, inflammatory bowel disease, and juvenile arthritis. EXPOSURES Systemic antibacterial prescriptions and infections of the skin and other sites within 2 years before psoriasis diagnosis. MAIN OUTCOMES AND MEASURES Incident psoriasis as determined by validated diagnostic codes. The association of antibiotic exposure and infections with incident psoriasis was determined by conditional logistic regression, adjusting for confounders. RESULTS After adjusting for matching, country, socioeconomic deprivation, outpatient visits, and infections within the past 2 years, antibiotic exposure in the last 2 years was weakly associated with incident psoriasis (adjusted odds ratio [aOR], 1.2; 95% CI, 1.0-1.5). The associations for infections of skin (aOR, 1.5; 95% CI, 1.2-1.7) and other sites (aOR, 1.3; 95% CI, 1.1-1.6) were similar. Untreated nonskin infections (aOR, 1.5; 95% CI, 1.3-1.8) but not antibiotic-treated nonskin infections (aOR, 1.1; 95% CI, 0.9-1.4) were associated with psoriasis. Results were similar when using a lifetime exposure window. Different classes of antibiotics and age of first antibiotic exposure were also not associated with psoriasis. The findings did not substantively change when excluding periods of varying length before diagnosis. CONCLUSIONS AND RELEVANCE Infections are associated with the development of pediatric psoriasis, but antibiotics do not appear to contribute substantially to that risk. Copyright 2016 American Medical Association. All rights reserved.