Observations of nemaline bodies in muscle biopsies of critically ill patients infected with SARS-CoV-2

Patients infected with SARS-CoV-2 who have been admitted to the intensive care unit (ICU) often face months of physical disability after discharge. To optimize recovery, it is important to understand the role of musculoskeletal alterations in critically ill patients infected with SARS-CoV-2. The main aim of the present study was to describe the presence and morphology of nemaline bodies found in skeletal muscle tissue from critically ill patients infected with SARS-CoV-2. In n=7 patients infected with SARS-CoV-2, ultrastructural characteristics of vastus lateralis muscle obtained on days 1-3 (T0) and days 5-8 (T1) following ICU admission were investigated in more detail with electron microscopy. Those muscle biopsies consistently showed variable degrees of myofiber necrosis and myofibrillar disorganisation. In 4/7 (57%) patients at T1, the Z-line material accumulated into nemaline bodies with a typical lattice-like appearance at higher magnification, similar to that found in nemaline myopathy. This study is the first to describe the disintegration of myofibrils and accumulation of Z-line material into nemaline bodies in skeletal muscle tissue obtained from critically ill COVID-19 patients following ICU admission, which should be interpreted primarily as a non-specific pathological response of extreme myofibrillar disintegration associated with myofiber necrosis. Mini abstract This study describes the presence and morphology of typical nemaline bodies in skeletal muscle ti0ssue from critically ill patients infected with SARS-CoV-2, which should be interpreted primarily as a non-specific pathological response of extreme myofibrillar disintegration associated with myofiber necrosis.