In this Viewpoint recently published in Lancet Rheumatology, the authors summarised the immune mechanisms of pulmonary intravascular coagulopathy in COVID-19 pneumonia. Indeed, the lung pathology seen in patients with COVID-19 shows marked microvascular thrombosis and haemorrhage, linked to extensive alveolar and interstitial inflammation that shares features with macrophage activation syndrome (MAS). The authors termed the lung-restricted vascular immunopathology associated with COVID-19 as diffuse pulmonary intravascular coagulopathy, which in its early stages is distinct from disseminated intravascular coagulation. Increased circulating D-dimer concentrations and elevated cardiac enzyme concentrations in the face of normal fibrinogen and platelet levels are key early features of severe pulmonary intravascular coagulopathy related to COVID-19. Extensive immunothrombosis over a wide pulmonary vascular territory without confirmation of COVID-19 viraemia in early disease best explains the adverse impact of male sex, hypertension, obesity, and diabetes on the prognosis of patients with COVID-19. The immune mechanism underlying diffuse alveolar and pulmonary interstitial inflammation in COVID-19 involves a MAS-like state that triggers extensive immunothrombosis, which might unmask subclinical cardiovascular disease.
by Marialuisa Zedde and Francesco Cavallieri