The pathogenesis of
allergic reactions to
heparin is poorly understood. Clinically, this phenomenon is relevant because of its increasing incidence and the resulting therapeutic challenges due to various cross-reactions between unfractionated and low-molecular weight heparins as well as between heparins and
heparinoids. A 44-year-old female patient had developed a delayed-type
hypersensitivity to
certoparin-sodium. Diagnostic
allergy testing revealed various cross-reactions between different heparins as well as an intolerance to
heparinoids. After subcutaneous challenge with the recombinant
hirudin lepirudin (
Refludan) the patient developed a local
Arthus reaction at the injection site. In general, recombinant
hirudins do not cross-react with high- or low-molecular weight heparins and
heparinoids because of a different molecular structure and are therefore an alternative in case of adverse reactions to heparins and
heparinoids. Whereas a local
Arthus reaction has already been described twice for low-molecular weight heparins, this is to the best of our knowledge the first observation of a superficial
leukocytoclastic vasculitis due to s.c. applied
lepirudin.
Intravenous administration of heparins and
heparinoids in case of
hypersensitivity to these drugs following topical application risks a generalized eczematous reaction in patients with delayed-type
allergy to both groups of substances. In our patient with delayed-type
hypersensitivity to heparins and
heparinoids and superficial
vasculitis due to
lepirudin, the intravenous challenge with
heparin and a
heparinoid was justified as an ultima ratio measure and proved to be the useful therapeutical alternative.