ABSTRACT
Introduction: SARS-COV2 infection has come to focus in 2020, when COVID-19 was declared pandemic worldwide. In addition to interstitial pneumonia, its physiopathology involves multiple mechanisms, mainly inflammatory dysregulation and thrombo-inflammation, affecting most tissues and organs. Unexpected manifestations have been described, both in the acute phase and later, as a post-infectious disease. Case descriptions: Our study focuses on muscle biopsies obtained from 4 post-COVID-19 patients who had recovered from the infection, when muscle symptoms emerged, all with very high CPK levels. Two were females, 7th decade of life, presenting mild to moderate respiratory symptoms that resolved within a few days. About a month later they developed weakness and biopsies showed necrotic fibers in different proportions, one with features of rhabdomyolysis. Treatment with immunosuppressants and immunoglobulin resulted in significant improvement in motor and sensory conditions. The third patient, a 49-year-old hypertensive, obese and diabetic male, had severe respiratory symptoms requiring orotracheal intubation. Discharged without symptoms, he developed severe muscle weakness and tetraparesis one month after the COVID- 19 onset. Muscle biopsy showed degenerate and regenerating fibers and CD8 lymphocytic infiltration. Immunostaining for SARS-COV2 was negative. Treatment with methylprednisolone and immunoglobulin was followed by improvement of symptoms, of inflammatory markers, and decrease in muscle enzymes. The forth one, a 53-year-old hypertensive and diabetic male, developed weakness and skin lesions 3 - 4 weeks after COVID-19 diagnosis. Muscle biopsy showed perifascicular atrophy and myofiber vacuolization, suggestive of dermatomyositis. Conclusion: Our observations, in correlation with clinical history, biopsy findings and negative immunohistochemical results for COVID-19, strongly suggest the possibility of post-infectious myopathies.