Version July 2025
AAE-C1INH: acquired angioedema with C1INH deficiency; ACE: angiotensin-converting enzyme; C1INH: C1 inhibitor; C1q: complement component C1q; C4: complement component 4; HAE: hereditary angioedema; NSAID: nonsteroidal antiinflammatory drug.
* C4 is usually <50% of normal in patients with HAE-C1INH. 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 discussion within the UpToDate topic on the pathogenesis and diagnosis of hereditary angioedema.
Δ Refer to the differential diagnosis discussion within the UpToDate topic on the pathogenesis and diagnosis of hereditary angioedema.
◊ Mutations in a growing number of genes can cause HAE with normal C1INH. Refer to UpToDate topic on hereditary angioedema with normal C1 inhibitor.
