What initial investigations should I consider for a patient with recurrent episodes of angioedema?

Initial investigations for a patient presenting with recurrent episodes of angioedema should focus on identifying the underlying cause or trigger to prevent further episodes ¹.

• Medication Review: Immediately stop any angiotensin-converting enzyme (ACE) inhibitor treatment, as drug-induced angioedema can persist for several months after cessation ¹. Angiotensin-II receptor antagonists should also be avoided if possible, as they can trigger episodes ¹.
• Allergy-Focused Clinical History: A thorough allergy-focused clinical history should be taken, tailored to the presenting symptoms ³. This includes details such as any personal or family history of atopic disease (e.g., asthma, eczema, allergic rhinitis), foods that are avoided, the age when symptoms first started, the speed of symptom onset after contact with a potential trigger, duration and severity of reactions, frequency of occurrence, and reproducibility of symptoms on repeated exposure ³.
• Physical Examination: Conduct a physical examination, paying attention to growth, signs of malnutrition, and signs indicating allergy-related comorbidities like atopic eczema, asthma, or allergic rhinitis ³.
• Specific IgE Testing: If IgE-mediated allergy is suspected based on the clinical history (particularly in children and young people), consider offering skin prick tests and/or blood tests for specific IgE antibodies to suspected foods and likely co-allergens ³. These tests should only be performed by healthcare professionals with appropriate competencies and facilities to manage an anaphylactic reaction ³.
• Mast Cell Tryptase Testing: If the recurrent angioedema episodes involve features of a suspected anaphylactic reaction, timed blood samples for mast cell tryptase testing should be considered ². A sample should be taken as soon as possible after emergency treatment, and a second sample ideally within 1 to 2 hours (but no later than 4 hours) from the onset of symptoms ².
• Referral for Specialist Investigation: Refer the patient to a dermatologist or immunologist if hereditary or acquired angio-oedema is suspected, if symptoms persist or reoccur 3 months after stopping an ACE inhibitor, or if the cause of angio-oedema is not identifiable or avoidable ¹. Specialist review may be indicated to identify associated conditions, trigger factors, or to exclude differential diagnoses ¹.