Her laboratory results showed that her complement levels were within normal limits despite clinical symptoms. This situation leads to the specific variant of hereditary angioedema called hereditary angioedema with a normal C1 esterase inhibitor (HAE-NI-C1-INH). Although there are currently no approved treatments, positive responses have been seen to her use of C1-INH concentrate and tranexamic acid to alleviate both immediate and delayed symptoms. Here, C1S is linked to hereditary angioedema.