PF4 and Venous thrombosis: These two types of skin lesions are due to intradermal microvascular thrombosis, possibly explained by the presence of FcγRIIa receptors on the endothelial cells of the superficial dermal vascular plexus [8], which are similar to those on platelets and bound by the ternary complexes of antibody-heparin-platelet factor 4.