Hereditary angioedema as a cause of recurrent abdominal pain in a pediatric patient with Crohn's disease.

Hereditary angioedema (HAE) is a rare genetic condition caused by deficient or dysfunctional C1 inhibitor protein (C1INH) resulting in episodic angioedema of the skin, upper airway, and gastrointestinal tract. HAE most often presents within the first two decades of life and may cause severe abdominal pain, nausea, diarrhea, and emesis, making it an important diagnosis for pediatric gastroenterologists to consider. Here, we report the case of an 11-year-old boy with a history of Crohn's disease who presented with recurrent episodes of acute epigastric and periumbilical pain despite evidence of endoscopic, histologic, and radiographic remission. These pain episodes lasted 12-48 h, were associated with nonbloody, nonbilious emesis, and prompted several visits to the emergency department. Abdominal exam and imaging were repeatedly unremarkable, and bloodwork was notable only for mildly elevated C-reactive protein (<10 mg/L). Eventually, the patient presented with acute facial edema and was referred to Immunology for workup of suspected HAE. Bloodwork revealed low C4 and C1INH concentration, confirming the diagnosis of HAE type I, and the patient was started on appropriate pharmacotherapy to good effect. This case highlights the importance of investigating alternative diagnoses in patients with adequately treated inflammatory bowel disease who continue to experience gastrointestinal symptoms and exemplifies common gastrointestinal manifestations of HAE.