Hereditary angioedema (HAE) due to an inherited C1-inhibitor (C1-INH) deficiency causes localized swelling of the oral cavity, pharynx, larynx, and face, that may be life-threatening when the larynx is involved. A 26-year-old woman seen 3 times previously for pharyngeal or laryngeal edema while in her teens, and seen this time for dyspnea was found in computed tomography (CT) to have esophageal edema and pleural effusion. Her C1-INH activity was low, yielding a definitive diagnosis of HAE for her 10-year-plus-disease history. n mind in th e f idiopathicedema. should be kept i While it is comparatively rare, HAE differential diagnosis o