The rate of thrombotic complications in COVID-19 patients is high and could be associated with the risk of unfavourable outcomes. Moreover, pulmonary thrombotic events can occur even in patients already on anticoagulant treatment. We present the case of a patient with severe COVID-19 pneumonia, without traditional risk factors for thrombosis, who developed massive pulmonary thrombosis (PT) despite therapeutic anticoagulation. The diagnosis was challenging, and the case raised concerns about the protective role of conventional anticoagulant treatment in COVID-19 pneumonia. Thus, we searched for literature reports on COVID-19 patients who developed PT despite being under anticoagulation therapy. We identified 13 cohort studies including 4058 patients of which 346 (8.5%) developed PT and nine case reports/series enrolling 14 patients. Four cohorts were further analysed, which reported data on risk factors for thrombosis, outcomes and biological characteristics. We found that there were no differences between patients with and without PT regarding the classical risk factors for thrombosis. PT occurred regardless of the anticoagulation regimen, and the risk factor identified was severe COVID-19 pneumonia and a stay in an intensive care unit (ICU). Pulmonary thrombotic events in patients with COVID-19 are rather inflammation-related than correlated with traditional thromboembolic risk factors, and the therapeutic approach must take into consideration this aspect.
Keywords: COVID-19 pneumonia; anticoagulation; inflammation; pulmonary thrombosis; risk factors.