Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief, 2023.
Edited by the DermNet content department
This 80-year-old lady has atrial fibrillation and has been on warfarin for 2 years. Her anticoagulation control has been erratic in the last months.
She has developed extremely painful, bruised areas on her leg in the last 48 hrs.
These acute haemorrhagic lesions are the early stages of coumarin necrosis.
Shortly after initiation of a coumarin, there may be a temporary state of thrombophilia, as coumarin reduces the effect of both natural anticoagulants and coagulants. The former (Proteins C and S) have shorter half-lives than the coagulants, hence the early temporary thrombophilic state before anticoagulation is effected. The same situation may occur with longstanding coumarin use if control has been erratic. It is more likely to develop if heparin is not used in the early initiation of coumarins, or if the coumarin loading dose is too high.
Lesions tend to occur on the fatter areas of the body such as the thighs and breasts.
The coumarins should be stopped and heparin initiated. The condition does not occur with newer oral anticoagulants.
Ulceration is likely to happen; surgical debridement may be required.
