COL18A1 and hereditary angioedema: Comparing patients with HAE nC1-INH to patients with AE-UNK, in the three months before HAE treatment initiation, there were significantly fewer patients with AE-UNK experiencing angioedema attacks affecting their extremities (38% vs. 13%, p = 0.045) and GI system (57% vs. 22%, p = 0.015; Table 2).