With interest we read the article by Hooper et al. about the histopathological and ultrastructural findings on autoptic muscle biopsy in a ~60yo female with a previous history of pre-diabetes, arterial hypertension, and hyperlipidemia, who experienced a fatal infection with SARS-CoV-2, manifesting as interstitial pneumonia requiring intubation and artificial ventilation [1]. She died one week after having been tested positive for SARS-CoV-2 from intractable arterial hypotension, bradycardia, and respiratory and metabolic acidosis [1]. Histology of the skeletal muscle revealed fibrin micro-thrombi, perimysial micro-hemorrhages, adjacent vacuolar degeneration and necrosis, and minimal inflammatory infiltration [1]. Electron microscopy revealed degenerated cells with cytoplasmic condensation, degenerated mitochondria, and cytoplasmic clusters of SARS-CoV-2 particles [1]. We have the following comments and concerns.

Involvement of the skeletal muscle in COVID-19 may not only manifest as myalgia, fatigue, or elevation of serum creatine-kinase (CK) but also as muscle weakness, atrophy, dermatomyositis, critical ill myopathy, myasthenia, myasthenic syndrome, or rhabdomyolysis [2-4].

Missing in the report is the medication the patient received since hospitalisation. Since some of the compounds given to treat COVID-19 are myotoxic (e.g. steroids, chloroquine, azithromycin) [5], it is crucial to know the drugs given since admission. The influence of these compounds on muscle morphology should be discussed.

Since SARS-CoV-2 may affect peripheral nerves and secondarily the skeletal muscle [6,7], we should know if the abnormalities detected on autopsy were attributable to neuropathy and concomitant myopathic changes. The results of nerve conduction studies (NCSs) and needle electromyography (EMG) should be provided.

We should know if the patient complained about any neuromuscular symptoms already on admission and the medication the patient was regularly taking prior to admission, missing in this respect is the discussion about neuromuscular compromise already prior to admission. Did the patient suffer from a subclinical neuromuscular disorder (NMD) already before hospitalisation? 

Missing is a discussion about the discrepancy between the mild abnormalities on muscle histology and the sometimes-severe muscle compromise, even leading to muscle weakness and rhabdomyolysis. According to the presented morphological abnormalities, myopathy in COVID-19 patients is rather due to side effects from the treatment applied, pre-existing, subclinical muscle pathology, or due to secondary immune-mechanisms than from viral myositis. 

Thrombo-embolic events are a common complication of SARS-CoV-2 infections [8]. We should know if pulmonary embolism, as detected on autopsy, was already detected intra vitam and if the patient received anticoagulation. 

Overall, this appealing autopsy study has some limitations, which need to be addressed before drawing conclusions. Muscle damage due to drugs given for COVID-19 or prior to admission, previous NMD, and nerve damage with secondary muscle pathology need to be excluded. The findings suggest that severe muscular compromise in COVID-19 is rather due to non-viral pathophysiology than due to viral myositis.