SERPING1 and hereditary angioedema: Among patients with HAE-C1-INH aged ≤ 1 year, 66.7% (8/12) had low C1-INH levels [mean 14.2 mg/dL (range 4.9–46.2)], while 91.7% (11/12) had reduced fC1-INH [mean: 30.8% (range 3.6–101.4)].