Pulmonary stromal expansion and intra-alveolar coagulation are primary causes of COVID-19 death

Area of Science:

• Pathology
• Immunology
• Virology

Background:

• While many COVID-19 deaths are in older individuals from comorbidities, the direct impact of SARS-CoV-2 on younger patients requires detailed examination.
• Understanding the specific pathological mechanisms in fatal COVID-19 cases is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the detailed autopsy findings in patients who died from COVID-19 acute respiratory distress syndrome (ARDS).
• To identify the primary sites of viral replication and the nature of the inflammatory and regenerative responses in the lungs.

Main Methods:

• Performed twelve complete autopsies, including two rapid autopsies on young patients with COVID-19 ARDS as the cause of death.
• Conducted histological and cellular analyses to identify viral presence, inflammatory cell infiltration, coagulation patterns, and tissue regeneration.

Main Results:

• COVID-19 ARDS pathology was predominantly in the lung parenchyma, not airways, with viral replication in pneumocytes and macrophages.
• Coagulation primarily occurred within the alveoli, involving aggregated platelets, and was associated with massive CD163+ macrophage accumulation and lymphocyte depletion.
• Lung consolidation resulted from significant regenerative processes including stromal/epithelial proliferation and neovascularization.

Conclusions:

• COVID-19 ARDS involves unique intra-alveolar coagulation, specific inflammatory profiles, and extensive lung regeneration.
• Therapeutic strategies inhibiting platelet aggregation, angiogenesis, and general cell proliferation may be beneficial for advanced COVID-19 ARDS.