Factors Associated with Severe Skin Infections in Patients Treated with Biologic Therapies for Inflammatory Rheumatic Diseases

BACKGROUND: The incidence of severe infections is increased under biologic therapies and the skin is the second localization. OBJECTIVE: To appraise the factors associated with severe skin infections (SSI) in patients under biologic therapies for inflammatory rheumatic diseases (IRD). METHODS: We performed a case-control (ratio 1:3) study nested in a prospective cohort of patients with IRD. SSI was defined as requiring hospitalization or intravenous anti-infectious therapy. We defined two imbedded periods: period A was the time window between the first biologic therapy and the SSI; period B was the last 3 or 12 months (for tumor necrosis factor blockers or rituximab, respectively) before the SSI. RESULTS: Among 4,361 patients with IRD, 29 had a SSI under biologic therapy. In multivariate analyses, SSI were significantly associated with smoking, baseline C-reactive protein and gammaglobulinemia, non-steroidal anti-inflammatory drugs before biologic therapy, cumulative dose of steroids, concomitant steroids during period A, number of different biologic therapies during period A, treatment with infliximab during period A, period B or as first biologic therapy and treatment at high dose during period B. CONCLUSION: In patients under biologic therapies for IRD, the risk of SSI is associated with several factors including tobacco, treatment with infliximab or high dose range.