Evaluation of a patient with symptoms suggestive of hereditary angioedema (HAE) but without a strong family history and with NORMAL complement studies

HAE: hereditary angioedema; ACE: angiotensin-converting enzyme; NSAID: nonsteroidal anti-inflammatory drug; C1-INH: C1 inhibitor; C1: complement factor 1; C4: complement factor 4; ACEI: ACE inhibitor.
* It may take several months to see the impact of discontinuation of ACEI and if suspicion is otherwise high, proceed with complement studies. Note that ACEI and NSAIDs can "unmask" HAE, so patients can have HAE exacerbated by ACEI or NSAIDs.
¶ If allergy cannot be excluded, refer to allergist or perform testing for suspected allergy.
Δ In the presence of normal C4, low C1-INH protein levels are usually due to laboratory error. Repeat.
◊ Examples of high-dose antihistamine regimens are found in the text of the topic on HAE with normal C1-INH.
§ Known HAE-specific mutations include variants in the genes for factor XII, angiopoietin-1, plasminogen-1, kininogen-1, myoferlin, and heparan sulfate-glucosamine 3-O-sulfotransferase 6.