Patients with HAE-C1INH-Type2 showed similarly low C4 levels (median: 10.1 mg/dL; range: 5.0–17.1), while C1INHq levels were elevated (median: 31.8 mg/dL; range: 10.8–70.0), consistent with the known biochemical profile of this subtype. Here, C4A is linked to hereditary angioedema.