Constitutive hyperhistaminaemia: a possible mechanism for recurrent anaphylaxis

The process underlying anaphylaxis involves an uncontrolled elevation in bl ood levels of mediators, including histamine. Usually, these abnormal level s are attributed to the degranulation of basophils and mast cells. Few repo rts have assessed the contribution of defects in histamine pharmacodynamics to allergic responses. In this report we describe a patient with recurrent anaphylaxis who was initially suspected to have enhanced histamine intoler ance. We evaluated urine and blood samples collected from this patient and from control individuals using an ELISA test. Our data clearly show constit utive hyperhistaminaemia and a markedly impaired urinary histamine clearanc e ratio in the index patient. It is suggested that this defect facilitates anaphylaxis.