Low molecular weight heparins (LMWHs) are used for a variety of indications. The most common type of hypersensitivity reactions to LMWHs are delayed-type hypersensitivity reactions (DHR). Immediate-type hypersensitivity reactions (IHR) occur only sporadically. Cross-reactivity of different LMWHs is a common and unpredictable problem. We present 2 cases of patients who developed DHR to nadroparin and enoxaparin, respectively. The third case presents a patient who developed IHR to nadroparin. Skin tests confirmed the hypersensitivity in all cases. In the cases of DHR, a skin test negative LMWH was identified and was tolerated in a challenge test. In the IHR case, cross-reactivity to all tested LMWHs was established. We hypothesize that the degree of cross-reactivity might depend on the type of hypersensitivity reaction with immediate reactions linked to more extensive cross-reactivity than delayed reactions. This is important to consider because, at least in some cases, a safe alternative LMWH can be identified.
Keywords: cross-reactivity; delayed-type hypersensitivity reactions; héparines de bas poids moléculaire; immediate-type hypersensitivity reactions; low molecular weight heparins; réactions d’hypersensibilité immédiate; réactions d’hypersensibilité retardée; réactivité croisée; skin tests; tests cutanés.