[Idiopathic anaphylaxis]

Idiopathic anaphylaxis (IA) has been described as a clinical entity by North America authors. The symptoms are brisk and relapsing episodes of angioedema, urticaria, bronchospasm, digestive symptoms, cardio-vascular collapse. Adults, females more than males, are mainly concerned. The seriousness is linked to laryngeal angioedema or to hypotension. Nevertheless lethality is rare. The first step of the procedure is aimed at the detection of several rare pathologies mimicking IA: the paroxystic capillary leak syndrome induced by a monoclonal gammapathy or by a release of cytokines, a carcinoid syndrome, cutaneous or visceral mastocytosis, hereditary or acquired deficiency of C1 esterase inhibitor, relapsing benign flushes and factitious anaphylaxis. These diseases being excluded, the diagnosis of anaphylaxis is established, and the diagnostic process searches for exceptional causes: food allergy elicited by unusual trophallergens, exercise-induced anaphylaxis, allergy to parasitic antigens, to inhalants, or hormonal allergy. The negativity of thorough investigations establishes the plausibility of IA. Several unconfirmed pathogenic hypotheses have been put forward: abnormal easiness to non specific release of mediators from mast cells and/or basophils, anti-IgE antibodies as a specific kind of auto-immunity, angiotensin II deficiency. Treatment of emergency relies on self-administration of epinephrine. A daily therapeutic regimen using corticosteroids and anti-H1 drugs is currently prescribed and can be efficient, but no randomized studies have asserted the validity of this management. The lack of immunological studies, contrasting with numerous clinical reports, questions whether IA is really an entity or solely anaphylaxis in search of unknown eliciting allergenic agents.