[Angioedema: differential diagnosis].

Angioedema (AO) is a clinical syndrome defined by a local swelling of the deep dermis or subcutaneous/submucosal tissues. AO is of rapid installation, non-pruritic, always circumscribed and transitory without any sequellae. A swelling not fulfilling these characteristics is not an AO. Characterization of the bradykinic or histaminic mechanism should not be started until it is firmly established that the patient has an AO. Among differential diagnosis of AO, two clinical situations can be particularly misleading: generalized edema with flare and remission or with a subjective or objective localized predominance; permanent localized edema but with fluctuation during time. Diagnosis of AO should be questioned if the evolution is unusual or if there is a resistance to the treatment. Hereditary AO are rare diseases whereas histaminic AO are much more frequent (beware of overdiagnosis of a rare disease). Even in patients with a known and real AO, a differential diagnosis should be evoked when a new clinical manifestation is atypical or is treatment resistant.