SERPING1 and hereditary angioedema: While HAE type 1 and 2 are clinically indistinguishable, laboratory tests will make it possible to differentiate between these types: serum of patients with type 1 HAE will show a C1-inhibitor protein level of <50% of normal combined with a decreased functionality of C1-inhibitor, whereas patients with type 2 will have a decrease in C1-inhibitor functionality in the presence of normal or increased levels of C1-inhibitor protein.