Development of Dermatomyositis after Pfizer BioNTeh COVID-19 Vaccine: A Case Report.

Introduction: The Coronavirus Disease 2019 (COVID-19) pandemic led to the fast development of vaccines, which is considered a medical advance in healthcare. With the extensive vaccination campaign performed worldwide, many adverse events following immunization (AEFI) were reported. Most of them were flu-like symptoms, mild and self-limiting. However, serious adverse events, such as dermatomyositis (DM), an idiopathic autoimmune connective tissue disease, have also been reported.

Case presentation: In this report, we describe a case of skin erythema, edema, and diffuse myalgia attributed at first to Pfizer BioNTeh, COVID-19 vaccination, given the temporal relationship and the absence of significant medical history. The causality assessment score was I1B2. However, after completing the etiological assessment, an invasive breast carcinoma was identified, and we retained the diagnosis of paraneoplastic DM.

Conclusion: This study underlines the importance of completing the etiological assessment before attributing any adverse reaction to vaccination to maintain optimal patient care.