SERPING1 and hereditary angioedema: Comprehensive studies have identified BK as the principal mediator of vascular leakage in C1-INH-HAE-related swelling attacks (10, 62) Circulating levels of BK, markers of endothelial activation, prothrombin fragments, D-dimer (63), cytokines (e.g., TNF-α and IL-8), as well as neutrophil count and neutrophil-derived factors (e.g., elastase, myeloperoxidase, pentraxin 3) (64) are increased during attacks compared with symptom-free periods in C1-INH-HAE patients.