Phlegmasia cerulea dolens (literally: painful blue edema) is an uncommon severe form of deep venous thrombosis which results from extensive thrombotic occlusion (blockage by a thrombus) of the major and the collateral veins of an extremity. It is characterized by sudden severe pain, swelling, cyanosis and edema of the affected limb. There is a high risk of massive pulmonary embolism, even under anticoagulation. Foot gangrene may also occur. An underlying malignancy is found in 50% of cases. Usually, it occurs in those afflicted by a life-threatening illness. Phlegmasia cerulea dolens (literally: painful blue edema) is an uncommon severe form of deep venous thrombosis which results from extensive thrombotic occlusion (blockage by a thrombus) of the major and the collateral veins of an extremity. It is characterized by sudden severe pain, swelling, cyanosis and edema of the affected limb. There is a high risk of massive pulmonary embolism, even under anticoagulation. Foot gangrene may also occur. An underlying malignancy is found in 50% of cases. Usually, it occurs in those afflicted by a life-threatening illness. This phenomenon was discovered by Jonathan Towne, a vascular surgeon in Milwaukee, who was also the first to report the 'white clot syndrome' (now called heparin induced thrombocytopenia ). Two of their HIT patients developed phlegmasia cerulea dolens that went on to become gangrenous.