Most cases of angioedema turn out to not be HAE, because most swelling attacks are typically allergic reactions or swellings caused by something other than C1-inhibitor deficiency. Laboratory analysis of blood samples or genetic testing is required to establish the HAE diagnosis. There are two specific blood tests that confirm HAE:
- C1-inhibitor quantitative (antigenic)
- C1-inhibitor functional
The most common form of the disease – Type I – is characterized by low quantitative levels of C1-inhibitor and affects about 85 percent of patients. Type II HAE affects the other 15 percent of patients who have normal or elevated levels of C1-inhibitor, but the protein does not function properly.
Several investigators have noted a familial (and therefore inherited) angioedema in patients with normal levels of C1-inhibitor. Now found under the designation of “HAE with Normal C1 Inhibitor”, this form of angioedema is yet to be fully understood.
HAE with Normal C1-Inhibitor, four types and counting: