Angioedema Without Wheals: Challenges in Laboratorial Diagnosis

Area of Science:

• Immunology
• Genetics
• Biochemistry

Background:

• Angioedema (AE) is a common symptom, often presenting with urticaria, but recurrent AE without urticaria poses diagnostic challenges.
• Hereditary and acquired angioedema (HAE/AAE) subtypes share similar clinical presentations, leading to misdiagnosis due to limited access to specific laboratory tests.
• Current diagnostic approaches for HAE with C1 inhibitor deficiency rely on complement evaluation, which may not be universally accessible or correctly performed.

Purpose of the Study:

• To review and highlight the diagnostic challenges in differentiating various types of angioedema, particularly bradykinin-mediated AE.
• To explore novel diagnostic tools and biochemical markers for identifying the underlying mechanisms of angioedema.
• To emphasize the need for improved and validated diagnostic tests to enhance accuracy and patient care.

Main Methods:

• Review of existing diagnostic methods for C1 inhibitor deficiency, including nephelometry, turbidimetry, radial immunodiffusion, chromogenic assays, and ELISA.
• Discussion of genetic sequencing for HAE with normal C1 inhibitor, targeting genes like F12 and PLG.
• Exploration of emerging biochemical tests for bradykinin-mediated angioedema, such as measuring cleaved high-molecular-weight kininogen and activated plasma kallikrein.

Main Results:

• Traditional complement assays are used for C1 inhibitor deficiency, but sample handling issues can lead to misdiagnosis.
• Dried blood spot (DBS) testing is proposed as an accessible method for diagnosing HAE with C1 inhibitor deficiency.
• Validated kallikrein-kinin system biomarkers show promise in differentiating AE mechanisms, though direct bradykinin measurements face challenges.

Conclusions:

• Accurate diagnosis of angioedema subtypes, especially bradykinin-mediated AE, requires improved and accessible laboratory testing.
• Novel approaches like DBS testing and kallikrein-kinin system biomarkers could significantly enhance diagnostic capabilities.
• Addressing variability in functional assays and developing specific tests are crucial for differentiating histaminergic from bradykinin-mediated angioedema.