Complement activation-related pseudoallergy (CARPA) has been reported as a hypersensitivity reaction, the symptoms of which fit into the Coombs and Gell's Type I category, that is not initiated or mediated by pre-existing IgE antibodies but arises as a consequence of activation of the complement system.15 Complement activation leads to the liberation of C3a, C5a and C5b-9, which triggers mast cells, basophils and other phagocytic cells, via their specific receptors, for the secretion of a score of vasoactive mediators. The gene discussed is C5; the disease is hypersensitivity reaction disease.