PF4 and COVID-19: Notably, in the two female patients of our series, the lung histopathological picture was overlapping and characterized by distinctive PF4-rich thrombotic phenomena inside the microcirculation (microthromboses), quite similar from a morphological point of view to those described in patients who have died from severe COVID-19, in which capillary dysfunction has been proven to interfere negatively with blood and tissue oxygenation [57,58,59].