Journal of internal medicine
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Systemic mastocytosis is a rare and chronic disorder characterized by a pathologically increased number of mast cells in various tissues and overproduction of mast cell mediators. From a group of 15 patients (10 females, 5 males) with systemic mastocytosis five female patients presented with a history of an anaphylactoid shock reaction to wasp sting. Three of them had no demonstrable specific IgE against wasp or bee venom in serum, and a skin test that was only weakly positive for wasp venom. ⋯ From the latter group two female and three male patients said they had been stung by a wasp in the past. Thus, anaphylactoid shock after Hymenoptera sting can be a presenting symptom of systemic mastocytosis and may be caused by an IgE- as well as a non-IgE-mediated mechanism. In cases of anaphylactoid reaction to Hymenoptera sting, especially when there is no IgE demonstrable in serum or in cases of intolerance of hyposensitization, the diagnosis of systemic mastocytosis should be considered, also in the absence of the clinical hallmarks of urticaria pigmentosa.