Clinicopathological Characteristics of Inflammatory Myositis Induced by COVID-19 Vaccine (Pfizer-BioNTech BNT162b2): A Case Report

Abstract

As more individuals were coronavirus disease 2019 (COVID-19) vaccinated, unexpected side effects appeared. Herein, we present the case of a 30-year-old man with myopathy in both extremities after the second dose of the Pfizer-BioNTech (BNT162b2) COVID-19 vaccine. Symptoms, swelling and pain, started from the proximal upper and lower extremities and extended to the distal parts. Although he underwent massive hydration, the muscle enzyme level continuously increased. He complained of dysphagia and dysarthria. Microscopically, muscle biopsy showed multifocal or scattered macrophage infiltration and degenerated myofibers. In contrast to general myopathy including inflammatory myositis and rhabdomyolysis, vaccine-induced inflammatory myositis shows a prolonged increase in muscle enzyme levels and multifocal macrophage infiltration with necrosis of the muscle fibers. Symptoms improved with glucocorticoid and immunosuppressive treatment. If vaccinated individuals experience severe and continuous muscle pain and swelling, clinicians should consider vaccine-induced inflammatory myositis, measure the muscle enzyme levels, and perform muscle biopsy for a definite diagnosis.

Keywords: Coronavirus; Inflammatory Myositis; Myopathy; Rhabdomyolysis; Vaccination.

Fig. 1. Erythematous purpuric plaques on the trunk (A) and both hands (B).

Fig. 2. Diffuse muscular enhancement on the adductor, quadriceps femoris, and hamstring muscles of both thighs (A) and the entire head and neck muscles (B) on enhanced magnetic resonance imaging.

Fig. 3. Histopathology of muscle biopsy in the thigh. Multifocal infiltrates (arrows) of large polygonal-shaped macrophages having amphophilic cytoplasm in the endomysium, intermingled with a few lymphocytes on hematoxylin and eosin staining (A). Multifocal and scattered macrophages infiltration in the perimysium, epimysium, and endomysium, confirmed by immunohistochemistry for CD68 (B). The degenerated or necrotic muscle fibers (arrows) demonstrated with Masson’s trichrome staining (C).