Supplementary Material for: Potassium Iodide for Cutaneous Inflammatory Disorders: A Monocentric, Retrospective Study

Objectives: Potassium iodide (KI) is a medication that has been used for decades in dermatology and it is mentioned as a treatment option in all major dermatology textbooks. Yet, there is little recent information on its efficacy. In our study, we wanted to retrospectively evaluate the therapy response to KI in our patients. Methods: The hospital information system was searched for patients treated with KI at the Department of Dermatology (University Hospital Zurich) in the last 20 years (January 1, 1998 to December 31, 2017). A total of 52 patients were found and, subsequently, 35 patients were included in our study. Results: KI was prescribed for the following skin conditions: erythema nodosum, disseminated granuloma anulare, necrobiosis lipoidica, nodular vasculitis, cutaneous sarcoidosis, and granulomatous perioral dermatitis/ rosacea. The median duration of KI intake was 5 ± 7.7 weeks (range 1–26). The global assessment of efficacy by the treating physician showed an improvement of disease in about a third of all patients. No response was seen in 14 patients and 9 even had a progression of disease. An adverse event was documented in 16 cases. Conclusions: Our findings show that an improvement was reached in only about a third of all cases. High response rates with only mild side effects (in 16 out of 35 patients) were observed.