[Erythema after subcutaneous heparin treatment]

Heparin-induced skin lesions are common. The majority are delayed-type hypersensitivity reactions to heparin or other components of the injection fluid. Differentiation from heparin-induced thrombocytopenia (HIT) skin lesions is important. The Warkentin 4T's score is helpful for assessment of the risk of HIT.

A 36-year old female was treated with injections of tinzaparin for a deep vein thrombosis. After 16 days, she developed progressive thrombocytopenia and a skin lesion at one of the injection sites. She was diagnosed with "skin lesion consistent with HIT and caused by the use of low-molecular-weight heparin". The platelet count returned to normal and the severity of the skin lesion improved after replacement of tinzaparin with fondaparinux.

In patients with skin lesions suspected of being caused by the use of heparin, a complete blood count needs to be made as quickly as possible. With a 4T's score ≥ 4, it is recommended that a skin biopsy and a laboratory HIT-test are performed. Heparin should be replaced by alternative anticoagulants by way of precaution.