Differential Diagnosis: Hereditary Angioedema is the Primary Diagnosis
This clinical presentation—colicky abdominal pain, vomiting, and non-pruritic facial/lip swelling following dental trauma in a patient with a prior similar episode—is pathognomonic for hereditary angioedema (HAE) until proven otherwise. 1, 2
Primary Diagnosis: Hereditary Angioedema (HAE)
The constellation of findings makes HAE the leading diagnosis:
- Recurrent episodes of angioedema without urticaria or pruritus affecting face and lips are characteristic of HAE, distinguishing it from allergic angioedema 1, 3
- Abdominal attacks occur in 43-93% of HAE patients, presenting as severe colicky pain with vomiting due to intestinal wall edema 3, 4
- Trauma triggers (dental extraction, bicycle accident) are well-established precipitants of HAE attacks 1, 3
- Self-limited resolution over 48 hours in the prior episode is typical of untreated HAE attacks 1
- Age of presentation (12 years old) fits the typical onset pattern, as HAE commonly manifests in childhood or adolescence 1
Diagnostic Confirmation Required
Obtain the following laboratory tests immediately:
- C4 complement level (will be low in >95% of HAE cases) 1, 2
- C1 esterase inhibitor quantitative and functional assays (diagnostic for HAE types 1 and 2) 1, 2
- CH50 (typically reduced) 2
Critical Management Considerations
Airway monitoring is mandatory as laryngeal edema can develop rapidly and cause asphyxiation—the leading cause of death in HAE 1, 3. The facial and lip swelling indicates potential for upper airway involvement 1.
Secondary Differential Diagnoses
Mast Cell Activation Syndrome (MCAS)
While less likely given the clinical pattern, MCAS should be considered:
- Requires episodic symptoms in ≥2 organ systems (gastrointestinal and dermatologic involvement present here) 5
- Key distinguishing features: MCAS typically presents with urticaria and pruritus, which are absent in this case 5
- Diagnostic criteria: Requires documented elevation of mast cell mediators (tryptase >baseline × 1.2 + 2 ng/mL, urinary histamine metabolites, or prostaglandin metabolites) during symptomatic episodes 5
- Triggers can include physical trauma, but the non-pruritic angioedema pattern strongly favors HAE over MCAS 5
Acute Appendicitis
Must be excluded given the lower quadrant tenderness:
- Most common surgical emergency in adolescents with abdominal pain, accounting for 50% of right lower quadrant pain presentations 6
- Distinguishing features: Appendicitis typically presents with fever, progressive worsening (not self-limited), peritoneal signs, and leukocytosis without facial swelling 6
- Imaging: Ultrasound is first-line if appendicitis remains a concern 6
Bowel Obstruction
Consider given the colicky pain pattern:
- Colicky pain results from increased peristalsis attempting to overcome obstruction 6
- Distinguishing features: Obstruction typically causes progressive distension, obstipation, and lack of facial swelling 6
- Imaging: CT abdomen/pelvis if clinical suspicion persists 6
Critical Pitfalls to Avoid
Do not perform unnecessary abdominal surgery. HAE patients have high rates of unnecessary appendectomy (23%), cholecystectomy (16.4%), and other abdominal surgeries due to misdiagnosis of acute abdomen 4. The combination of abdominal pain with facial angioedema should immediately raise suspicion for HAE rather than surgical pathology 2, 3.
Do not administer corticosteroids, antihistamines, or epinephrine as primary treatment for suspected HAE—these are typically ineffective for aborting acute attacks 1. If HAE is confirmed, acute treatment requires C1 esterase inhibitor concentrate or icatibant 7, 1.
Do not miss laryngeal involvement. Examine for stridor, voice changes, or dysphagia, as laryngeal edema can progress rapidly to complete airway obstruction 1, 3.