HAE differential diagnosis

Professor Andrea Zanichelli from Milan, Italy, gave the next lecture, dedicated to differential diagnosis in HAE. He started by looking at the recent history of diagnosis and understanding of HAE as a disease in which a chemical pathway in the body doesn’t work properly, leading to a deficiency of C1-inhibitor and consequent swelling from fluid leaking out of blood vessels and into the tissues.

Despite this, Prof Zanichelli said, patients still face a long delay in diagnosis, averaging 8 years, and some more than 10 years. In that time, almost half of patients are misdiagnosed, as the symptoms of HAE look like those of more common conditions, such as abdominal attacks being mistaken for appendicitis.

Also important, Prof Zanichelli said, was distinguishing between HAE and other forms of swelling caused by allergic reactions (mast cell-mediated). The diseases may look similar, but the mechanisms are very different. HAE is not itchy. It does not respond to allergy medicines. It often has no clear trigger, unlike mast cell-mediated angioedema.

To start with, Prof Zanichelli suggested asking about urticaria (itching). If there’s swelling with itching, then it’s probably allergic angioedema. If there’s a response to antihistamines or a more specialist drug called omalizumab, it is unlikely to be HAE.

The next step would be to check if the angioedema is caused by the use of a medication, most commonly a class of heart medications known as ACE-inhibitors. If that’s not the case, and especially if there’s evidence of a family history of unexplained swellings, then suspect HAE.

The presentation then extended into diagnostic tools and tests for HAE, including C1-inhibitor levels and the function of C1 and C4. This could also support a diagnosis of HAE with normal C1-inhibitor when an appropriate genetic test is conducted.

Finally, Prof Zanichelli presented a case study to illustrate differential diagnosis in angioedema.

Questions from the assembled audience followed the presentation, including whether CT scans and ultrasound are reducing the incidence of HAE misdiagnosis and the challenges of diagnosing solely based on abdominal symptoms.