Idiopathic anaphylaxis: classification, evaluation, and treatment of 123 patients.

The manifestations, evaluation, treatment, and course of 123 patients with idiopathic anaphylaxis (IA) are described for a total of 374 patient years of our management. Observation of this group of patients resulted in the description and classification of IA as one or more episodes of generalized IA with multiple systemic manifestations or IA with life-threatening angioedema of the tongue or larynx. Therapy is based on the frequency of episodes. Acute therapy is appropriate for infrequent episodes, but prophylactic therapy is indicated for frequent episodes. In patients with frequent episodes, remissions can be induced and maintained with prednisone. Prolonged remissions may occur after prednisone is stopped. There have been no deaths from IA in patients managed by our service. By definition, there is no identifiable antigen responsible for episodes of IA, and there is no underlying disease in these patients. A mast cell basophil-activation mechanism is suggested. IA may represent the most severe form of a spectrum of diseases that include idiopathic urticaria and angioedema.