Dermatomyositis post vaccine against SARS-COV2.

Background: Dermatomyositis belongs to an infrequent group of diseases predominantly found in patients older than 40 years old and is characterized by dermal and muscular findings. This disease presents itself as proximal, ascending and symmetric weakness and typical dermatosis with findings such as elevated muscle enzymes, altered electromyography and typical changes in muscle biopsy; as of today, the etiology of the disease in unknown. The COVID-19 vaccine has been a fundamental tactic to achieve control of the coronavirus (SARS CoV2), and it's clear that the benefits of getting the vaccine overweight the risks that might come along with it. Although rare, all adverse effects should be reported, this could help us to understand the elusive pathophysiology of inflammatory idiopathic myopathy.

Case Presentation: In this text we will describe the case of a patient with dermatomyositis who was vaccinated against SARS CoV2 with BNT162b2 mRNA (Pfizer-BioNTech), showing a temporal relation between the vaccination and the beginning of her symptoms. We realized all the diagnostic approach to the suspected disease including electromyography, muscle biopsy and laboratory findings, corroborating the diagnosis. The patient received standard treatment for this disease (steroid therapy) and have a classic slow improvement.

Conclusions: Although it´s not possible to confirm a direct correlation between the vaccine and the onset of the disease, we considered that there are enough data to suspect that this could be a trigger event and therefore should always be considered a possible cause for a case of inflammatory idiopathic myopathy.