Risk is increased in smokers and in patients with renal failure or in solid organ transplant recipients. Can be unilateral (PMID 14595286). Severe cases can fatal due to asphyxia. Ecallantide and icatibant are significant additions to the management of angioedema-UAO cases with compromised airway patency (PMID 24096073, 25328718, 25635988, 25944565. Significant upper airway angioedema is a potentially life-threatening condition capable of causing asphyxia. Management include maintenance or airway patency. In recalcitrant cases, in addition to icatibant (PMID 22936825, 22944544, 25646708), C1-inhibitor concentrate (22944544) or fresh-frozen plasma (FFP) (PMID 15191027, 24096073) are indicated (PMID 18206518). A report indicates that patients on this class of medications may develop unusually severe oral allergy syndrome with mouth or throat swelling (PMID: 25727650). ACEI-associated angioedema may also involve the genitalia or intestines, causing cramping, diarrhea or an acute abdomen with or without systemic hypotension (PMID 11773949)