Materials and methods: A comprehensive literature search was performed to identify clinical features that are typical or atypical for six different RAE types, e.g. mast cell-mediated RAE/chronic urticaria (RAE-CU), bradykinin-mediated RAE including HAE with and without deficiency of C1-inhibitor, RAE due to acquired C1-inhibitor deficiency, ACE inhibitor-induced RAE, and idiopathic RAE. This evidence concerns the gene ACE and hyperinsulinemic hypoglycemia, familial, 4.