Реферат
BACKGROUND: According to previous reports, most cases of inflammatory myopathy following mRNA vaccination can be classified as idiopathic inflammatory myopathy (IIM), particularly dermatomyositis (DM), owing to their similar clinical features and courses. However, some patients have different clinical features and courses. We report a rare case of transient inflammatory myopathy involving the masseter muscle following the third dose of COVID-19 mRNA vaccination. CASE PRESENTATION: An 80-year-old woman presented with a history of fever and fatigue for 3 months soon after receiving the third COVID-19 mRNA vaccination. Her symptoms progressed to jaw pain and inability to open her mouth. She also experienced mild proximal muscle weakness in the lower limbs but no skin manifestations or daily difficulties. Fat-saturated T2-weighted magnetic resonance imaging showed bilateral high-intensity signals for the masseter and quadriceps muscles. The patient experienced spontaneous resolution of fever and improvement of symptoms 5 months after onset. The timing of the onset of symptoms, the lack of detectable autoantibodies, and the atypical presentation of myopathy in the masseter muscles, in addition to the spontaneous mild course of the disease, all indicate the substantial role of mRNA vaccination in this myopathy. Since then, the patient has been followed up for 4 months without any recurrence of symptoms or any additional treatment. CONCLUSION: It is important to recognize that the course of myopathy after COVID-19 mRNA vaccination could be different from that of typical IIMs.