How is HAE diagnosed?
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% of patients. Type II HAE affects the other 15% 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. In women, swellings have been correlated with pregnancy or the use of oral contraceptives; however, affected male family members have also been identified. Some scientists believe that a mutation in the gene for human coagulation Factor XII may be a potential cause of swelling in these patients with familial estrogen-exacerbated angioedema.
At what age does HAE attacks start?
The age of HAE onset varies considerably, however, in one study, half of the patients reported onset of their symptoms by the age of seven, and over two thirds became symptomatic by the age of thirteen. There also seems to be an increased frequency of attacks during puberty or adolescence.