This 42-year-old black female presents to the emergency department (ED) 2 hours after the onset of facial swelling that has now progressed to difficulty in breathing.
She has no previous history of tissue swelling and there is no family history of disorders characterized by tissue swelling. Her past medical history is remarkable only for newly diagnosed hypertension. She is otherwise healthy, without any history of drug allergies. Last week, her primary care physician started her on lisinopril, an angiotensin-converting enzyme inhibitor (ACEI) antihypertensive.
Upon presentation to the ED, her vital signs are as follows: heart rate 100 bpm, respiratory rate 22 bpm, blood pressure 165/90 mmHg, oxygen saturation 96% on room air, and temperature 37°C.
The patient is seated upright (Figure 27.1) with markedly edematous lips and face. She has a muffled voice (“hot potato voice”) and is having difficulty swallowing her own secretions. There is no audible stridor. The remainder of the physical examination is within normal limits.
What Is the Pathophysiology of Angioedema?
Angioedema is characterized by the abrupt onset of localized, transient, nonpitting swelling of the skin, deep subcutaneous tissues, and mucosal membranes of the upper respiratory and gastrointestinal tracts. Affected areas may be erythematous or skin-colored, and typically have ill-defined margins without urticaria. Angioedema develops due to a local increase in permeability of the submucosal or subcutaneous capillary vessels, causing local plasma extravasation into the interstitial space. This results in transient swelling of well-demarcated areas. This process is mediated by the localized or systemic release of vasoactive substances, most frequently histamine or bradykinin.1–4
Angioedema can progress rapidly, particularly with histamine-mediated reactions, and constitute a medical emergency when involving the oropharynx, pharynx, and larynx due to the imminent risk of airway obstruction. Importantly, this airway swelling may develop into a potentially difficult airway, making airway management such as intubation quite challenging. Although the presenting clinical signs and symptoms are similar, the biochemical cascade initiated by histamine is distinct from that mediated by bradykinin.5 Therefore, it is imperative that practitioners have a comprehensive understanding of the underlying pathophysiologic processes in order to appropriately treat patients presenting with angioedema.
How Is Angioedema Classified?
There are various classification schemes that attempt to organize the different forms of angioedema into a comprehensive yet useful structure. A biochemical basis for classification with a focus on the pathophysiologic processes will be discussed. In general, this approach organizes angioedema into allergic (immune) or nonallergic (nonimmune) forms. Specifically, allergic angioedema is mediated by histamine while the majority of nonallergic angioedema is mediated by increased plasma and tissue concentrations of bradykinin. Importantly, histaminergic reactions also include nonallergic hypersensitivity reactions, also ...