Skeletal muscles and Covid-19: a systematic review of rhabdomyolysis and myositis in SARS-CoV-2 infection

Objectives Myalgia is a widely publicised feature of Covid-19, but severe muscle injury can occur. This systematic review summarises relevant evidence for skeletal muscle involvement in Covid-19. Methods A systematic search of OVID and Medline databases was conducted on 16/3/2021 and updated on 28/10/2021 to identify case reports or observational studies relating to skeletal muscle manifestations of Covid-19 (PROSPERO: CRD42020198637). Data from rhabdomyolysis case reports were combined and summary descriptive statistics calculated. Data relating to other manifestations were analysed for narrative review. Results 1920 articles were identified. From these, 61 case reports/series met inclusion criteria, covering 86 rhabdomyolysis cases. Median age of rhabdomyolysis patients was 50 years, (range 6-89). 49% had either hypertension, diabetes mellitus or obesity. 77% were male. Symptoms included myalgia (74%), fever (69%), cough (59%), dyspnoea (68%). Median peak CK was 15,783U/L. 28% required intravenous haemofiltration and 36% underwent mechanical ventilation. 62% recovered to discharge and 30% died. Dyspnoea, elevated CRP and need for intravenous haemofiltration increased risk of fatal outcome. Additional articles relating to skeletal muscular pathologies include 6 possible concomitant diagnoses or relapses of idiopathic inflammatory myopathies and 10 reports of viral-induced muscle injuries without rhabdomyolysis. Localised myositis and rhabdomyolysis with SARS-CoV-2 vaccination have been reported. Conclusions Rhabdomyolysis is an infrequent but important complication of Covid-19. Increased mortality was associated with a high CRP, renal replacement therapy and dyspnoea. The idiopathic inflammatory myopathies (IIM) may have viral environmental triggers. However, to date the limited number of case reports do not confirm an association with Covid-19.