Clinical manifestations and progression, seasonal variation, and environmental factors associated with Paederus dermatitis among patients attending the outpatient dermatology clinic of Thailand's largest national tertiary referral center: a prospective cohort study

Abstract

Introduction: Paederus dermatitis (PD) is a skin reaction to a chemical substance called paederin, which emanates from a beetle of Paederus spp. This study’s objective was to investigate the clinical manifestations and progression, seasonal variation, and environmental factors associated with PD among patients attending the outpatient dermatology clinic of Siriraj Hospital. Methods: This prospective cohort study included patients who were diagnosed with PD at the Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand during the October 2017 to July 2018 study period. Sociodemographic and environmental data were collected by questionnaire. Results: Twenty-five PD patients (16 females, 9 males) were included with a mean age of 40.9 years (range 17–69 years). The most common sites were the upper and lower extremities. Erythema, linear, and kissing lesions (where two skin surfaces contact) were found in 100%, 32%, and 28% of patients, respectively. Seventy-six percent of patients demonstrated more than one lesion. Eighty percent of patients lived in Bangkok, and 44% of patients had a home near a farm or forest. Fluorescent lighting was used in the homes of 24 patients. All 25 patients were treated with topical steroid, and some received other supportive regimens. Two patients had post-inflammatory hyperpigmentation as a complication; only 7 of 25 patients attended the scheduled follow-up visit. Conclusion: In Thailand, PD presents throughout the year, but the most active month is December. Skin lesions vary from mild irritant dermatitis to severe dermatitis, and the average time to complete cure is 12 days. History and clinical manifestation are essential for accurate diagnosis.