Childhood infections as predisposing factors to developing psoriasis vulgaris into early adulthood

Abstract Background Psoriasis is a chronic inflammatory skin disease associated with an increased risk of developing cardiovascular disease. Various environmental factors contribute to psoriasis development in individuals who are genetically susceptible to the disease. Although infections have been associated with disease initiation and recurrence, the consequences of early exposure to infections, many years before disease manifestation, are unexplored. Objectives To investigate the effect of exposure to infections during formative years on the incidence of psoriasis through to early adulthood. Methods ABIS is a large birth cohort in which the parents of participating children have answered comprehensive questionnaires on their child’s exposure to infections and medication at different age intervals. Information regarding psoriasis was obtained from the Swedish National Patient Register, while data on medication were obtained from the National Prescribed Drug Register. Statistical analyses were performed with custom-written R scripts. Results Logistic regression analysis on 1-year follow-up data revealed that influenza was associated with an increased risk of developing psoriasis later in life [odds ratio (OR) 2.47, 95% confidence interval (CI) 1.32–4.39; P = 0.006]. In line with this, at the third-year evaluation, we found that participants who had tonsillitis at least once between their first and third year of life had an almost three times greater risk of developing psoriasis into early adulthood than controls (OR 2.90, 95% CI 1.46–5.56; P = 0.003). In contrast, at the 8-year evaluation, we found that psoriasis was less frequent in children who had experienced episodes of gastroenteritis between the ages of 6 and 8 years vs. control participants (OR 0.42, 95% CI 0.20–0.92; P = 0.003). Conclusions We demonstrate, for the first time, the effect of exposure to infections during the first years of life and the subsequent development of psoriasis extending into early adulthood. Our study indicates that early exposure to infections may influence the development of the adaptive immune system during formative years. This modulation is evidenced by the higher incidence of psoriasis observed in early adulthood, several years after the initial exposure.