Covid-19 Vaccine-Induced Myositis

Background/Aims Through the COVID pandemic there have emerged reports of autoimmunity or new rheumatic diseases presenting in patients after they had COVID-19. This is thought to be caused by cross-reactivity of the COVID-19 spike protein to human antigens. Given the use of mRNA COVID-19 vaccinations which express the spike protein we might expect to see presentation of new rheumatic diseases following their use. We discuss a case where this appears to have occurred. Methods Our patient is a 24-year-old male with mixed phenotype acute leukaemia who had been treated with allogenic stem cell transplant and was currently in remission. He presented with fevers, palpitations, myalgia and bilateral arm and leg swelling. Symptoms began the day after receiving the first dose of an mRNA COVID-19 vaccination (Pfizer/BioNTech.) There were no other symptoms or recent change in medications. Physical examination revealed tender oedema in his forearms, biceps and thighs bilaterally with sparring of the hands. He had reduced power with shoulder (MRC 3/5), elbow (4), wrist (4+) and hip (4) movements. Observations revealed tachycardia and fevers up to 40C. Results Laboratory studies showed markedly elevated C-reactive protein (202), creatinine kinase (6697) and troponin (593) whilst investigations for infection were negative. An autoimmune panel was positive for anti- PM-SCL-75-Ab. An electrocardiogram showed sinus tachycardia. Echocardiogram was normal. Bilateral upper limb dopplers revealed no deep vein thrombus. An MRI of his thighs showed diffuse symmetrical oedema within the muscles, in keeping with an inflammatory myositis. A quadricep muscle biopsy showed evidence of MHC class 1 up-regulation, suggesting an inflammatory process. In addition, there were numerous macrophages evident in the endomysium. While this can be seen in graft-versus-host disease (GVHD), they would usually be found in the perimysium. After discussion between haematology, rheumatology and neurology, this was felt to be a case of vaccine induced myositis and myocarditis. Autoimmune myositis was thought to be less likely due to the relative sparing of the hands and the absence of Raynaud's phenomenon. 1 gram of intravenous methylprednisolone was then given for 3 days. The patient had a marked response with defervescence, improving laboratory markers, improved myalgia and decreased limb swelling. The patient was stepped down to a reducing regime of prednisolone and discharged. Due to relapse whilst weaning he has started on mycophenalate mofetil and rituximab and now continues to improve. Conclusion There are case reports of myositis following COVID-19 vaccination but our patient's case is complicated by the differential diagnosis of GVHD and concurrent myocarditis. Ongoing work is needed to clarify the exact link between vaccination and the presentation of a new inflammatory myositis, but it is important to recognise and start treatment early in order to preserve muscle bulk and ensure recovery.

Unusual Myositis of the Temporalis Muscle Occurring with Acute Covid-19

Background. SARS-CoV-2 infection can be accompanied by neuromuscular disorders. Rhabdomyolysis and Guillain-Barre syndrome have been described repeatedly. There are case reports of inflammatory myopathies manifesting during COVID-19, presenting as dermatomyositis, polymyositis or immune-mediated necrotizing myopathy, with dermatomyositis-like presentations most commonly reported. Larger cases series are from postmortem examinations of COVID-19 patients, where variable inflammatory pathology of the skeletal muscle has been found frequently but without local detection of the actual virus. Thus, autoimmune mechanisms or the systemic interferon response are discussed as causes. We report a case of focal inflammatory myopathy with perimysial pathology of the temporalis muscle occurring with acute, but mild COVID-19. Methods. Case report of clinical observations, cranial MRI, histopathological, and laboratory findings. 3T cranial MRI was performed with gadolinium contrast. Open temporalis muscle biopsy was performed. The sample underwent standard cryohistological studies as well as immunohistochemistry with antibodies against MHC-I and II, CD3, CD4, CD19, CD68, anti-MAC, p62 and MxA. Testing for auto-antibodies was based on immunoblots or ELISA. RT-PCR for SARS-CoV-2 was run with RNA extracted from cryopreserved muscle. Results. A Caucasian woman in her 60s with no history of autoimmune or muscle complaints developed swelling and pain of the right jaw musculature five days after testing positive for SARS-CoV-2 due to respiratory tract symptoms. In addition, she experienced trismus, but no further neuromuscular complaints. The course of respiratory tract symptoms stayed mild. She had been vaccinated previously with single shot SARS-CoV-2 vector vaccine. Due to persistent swelling and complaints, giant cells arteritis was excluded by unresponsiveness to five days oral steroids and sonography of the temporal artery. Cranial MRI was performed nearly four weeks after the SARS-CoV-2 infection and showed marked swelling and oedema of the temporalis muscle. Its biopsy showed numerous CD68 and acid phosphatase positive cells infiltrating from perimysial perivascular foci towards the endomysium with perimysial damage but little damage of adjacent, perifascicular muscle fibres. Muscle fibres did not react with anti-MHC-II, anti-MAC or -MxA. Capillaries did not react with anti-MAC or -MxA. SARS-CoV-2 RNA was not detected in muscle tissue. Serum creatine kinase was not elevated in the subacute phase. Slightly elevated ANA titre led to detection of autoantibodies against proliferating cell nuclear antigen (PCNA). No pathological results for other autoantibodies, including myositis-specific antibodies and anti-ds-DNA, were found in blood. Neither were antibodies against hepatitis C and B viruses. Retesting 15 weeks after infection, anti-PCNA immunoblot was still positive, but ELISA did not indicate a pathologic titre. The swelling, myalgia and trismus regressed spontaneously a month after onset, yet the latter still persists at the time of reporting. Conclusion. Our case diverges from the majority of COVID-19 associated my-ositis reports in the unusual location of the focal myositis and the histopathological pattern of predominantly perimysial damage and histiocytic infiltration. It concurs with the literature as no SARS-CoV2 RNA could be detected in the muscle. Anti-PCNA is associated very rarely with myositis. Other associated disorder (systemic lupus erythematosus, chronic viral hepatitis B or C) were not found. Increased levels of autoantibodies are reported in COVID-19 and mostly attributed to loss of self-tolerance during the acute disease phase. Interestingly, the structural protein M of SARS-CoV-2 appears to interact notably with PCNA in infected cells. Still, the causal connection between the myositis and COVID-19 in this case is based on the close temporal association in the absence of alternative, competing explanations from the medical history and findings.