The dilemma of the negative skin test reactors with a history of venom anaphylaxis: will this always be the case?

The loss of sensitization over time, the involvement of a different pathogenetic mechanism and the poor sensitivity of diagnostic tests have been included among the causes of a non IgE-mediated anaphylaxis triggered by an insect sting. To provide further insight into this topic we describe the case of a patient suffering from urticaria pigmentosa, anaphylactic shock due to a Vespid sting and monosensitive to Polistes dominulus venom, who was previous diagnosed with non-IgE mediated insect sting anaphylaxis in subjects with urticaria pigmentosa. Therefore ultra-rush specific immunotherapy using an acqueous Polistes dominulus venom extract was performed over two mornings until a total dose of 100mcg was reached without any side effects. Presently the patient is undergoing maintenance therapy with a depot Polistes dominulus venom extract at 4-weekly intervals and is free of side effects. In conclusion, despite the high cross-reactivity among the venoms of the various species of Polistes, recent evidence of a selective specificity unique to European Polistes allergens raises the problem of the need to make the American Polistes venom as well as that of Polistes dominulus (a very common insect in Europe) available both for diagnostic and therapeutic purposes. Besides the fact that the presence of urticaria pigmentosa alone could have explained the anaphylactic reaction to the aspecific stimulation triggered by the venom, this case history also demonstrates that omitting to perform skin tests for Polistes dominulus venom would have led to the same misdiagnosis of non IgE-mediated anaphylaxis and served only to further delay commencing specific immunotherapy.