Evaluation of a patient with recurrent episodes of angioedema without hives (urticaria)

HAE: hereditary angioedema; ACE: angiotensin converting enzyme; C4: complement component 4; C1-INH: C1 esterace inhibitor; C1q: complement component C1q; NSAIDs: nonsteroidal antiinflammatory drugs.
* C4 is usually <50% of normal in patients with HAE-C1-INH. If results are not reported as a percentage of normal, then 25 mg is normal in adults, C4 <10 is definitely pathologic, C4 of 10 to 15 is possibly pathologic, and C4 >15 is not pathologic.
¶ Refer to the diagnostic errors section of the UpToDate topic on the pathogenesis and diagnosis of hereditary angioedema.
Δ Refer to the differential diagnosis section of the UpToDate topic on the pathogenesis and diagnosis of hereditary angioedema.
◊ Mutations in a growing number of genes can cause HAE with normal C1-INH. Refer to UpToDate topic on hereditary angioedema with normal C1 inhibitor.