Immediate Type Hypersensitivity to Heparins: Two Case Reports and a Review of the Literature.

Immediate type hypersensitivity reactions due to heparins are rare, and the exact immunologic pathomechanism has not been identified so far. In our 2 case reports, we describe first a 50-year-old female who received dalteparin (Fragmin®) and developed signs of an immediate type hypersensitivity reaction. The personal history revealed a previous application of dalteparin (Fragmin®). Evaluation with a skin prick test showed positive results for dalteparin. The second case deals with a 73-year-old female with a suspected immediate type reaction after the administration of dalteparin (Fragmin®). A skin prick test was negative but intracutaneous tests showed a positive reaction to the causative agent. Both cases indicated cross-reactivity reactions for low-molecular-weight heparin (LMWH) but not for unfractioned heparin (UFH) or fondaparinux. In conclusion, our case reports including a review of published cases of immediate type hypersensitivity reactions after the application of heparins illustrate this rare complication. Mostly, the causative agent can be identified with a skin test, which is highly suggestive of an IgE-mediated reaction. Therapeutic alternatives for patients with sensitization to an LMWH are UFH and fondaparinux. Both agents have a small risk of cross-reactivity compared to heparins of the same substance class.