Atypical Presentation of Erythema Nodosum Following Pfizer-BioNTech COVID-19 Vaccine

Background: Erythema nodosum (EN) is a common form of panniculitis that could be triggered by numerous conditions including infectious and non-infectious conditions. So far, few cases of EN caused by COVID-19 vaccine had been reported. Case Report: We report a case of atypical presentation of EN mimicking cellulitis in a patient who received the first dose of the Pfizer-BioNTech COVID-19 vaccine. A 38-year-old healthy woman who developed painful swelling on the left leg one week after receiving the first dose of Pfizer-BioNTech COVID-19 vaccine. Skin biopsy was revealed septal panniculitis. Due to the temporal association and the absence of other identifiable causes, Pfizer-BioNTech COVID-19 vaccine-related EN would be the most likely explanation. Conclusion: COVID-19 vaccines could be associated with rare side effects that should be reported for a better understanding of related outcomes of COVID-19 vaccination. This case was reported to keep in mind that EN can have atypical presentation as a rare side effect of COVID-19 vaccines.