Abstract
In covid-19, the basic lesion is interstitial pneumonia presenting as diffuse alveolar damage. However, unlike DAD/ARDS from other causes, there are several rather specific histopathological features: in the lung parenchyma, there is frequently a combination of all stages of DAD - acute, subacute, and chronic; platelet, and fibrin-rich thrombi are found in all types of pulmonary vessels - microcirculation, arteries, and veins, with formation of lung infarctions; the inflammation has a marked hemorrhagic character - alveolar bleeding; presence of atypical activated type II pneumocytes; unusual ("naked") megakaryocytes within the microvasculature; presence of virions in lung cells; and tendency to bacterial or fungal superinfection.
In the heart, no specific, reproducible histopathology of covid-19 myocardial injury has been shown at autopsy and the rates of fatal myocarditis are low.