Science News: Skeletal Muscle and Peripheral Nerve Histopathology in COVID-19

Submitted by: Niranjan N. Singh, MD, DM

Suh J, Mukerji SS, Collens SI, et al. Skeletal muscle and peripheral nerve histopathology in COVID-19. Neurology. 2021;97(8):e849-e858. doi:10.1212/WNL.0000000000012344

Summary: This study discusses spectrum of skeletal muscle and nerve pathology of patients who died following SARS-CoV-2 infection.

Psoas muscle and femoral nerve samples from 35 consecutive autopsies of patients who died following SARS-CoV-2 infection were collected and analyzed.

In SARS-CoV-2-positive patients, mean age at death was 67.8 years (range 43-96 years) and the duration of symptom onset to death ranged from 1-49 days. Four patients had neuromuscular symptoms. Peak creatine kinase was elevated in 74% (mean 959 U/L, range 29-8413 U/L). Muscle showed type 2 atrophy in 32 patients, necrotizing myopathy in 9, and myositis in 7. Neuritis was seen in 9. Major histocompatibility complex-1 (MHC-1) expression was observed in all cases of necrotizing myopathy and myositis and 8 additional patients. Abnormal expression of myxovirus resistance protein A (MxA) was present on capillaries in muscle in 9 patients and in nerve in 7. SARS-CoV-2 immunohistochemistry was negative in muscle and nerve in all patients. In the 10 controls, muscle showed type 2 atrophy in all patients, necrotic muscle fibers in 1, MHC-1 expression in non-necrotic/non-regenerating fibers in 3, MxA expression on capillaries in 2, and inflammatory cells in none, and nerves showed no inflammatory cells or MxA expression.

In summary, muscle and nerve tissue demonstrated inflammatory/immune-mediated damage likely related to release of cytokines. There was no evidence of direct SARS-CoV-2 invasion of these tissues.

Comments: This is an interesting study regarding pathology of SARS-CoV-2 infection presenting as nerve or muscle disease.  The study reveals that cause of muscle and nerve disease is likely immune mediated damage rather than direct viral infection.