Because of the possible involvement of the endothelial cell microenvironment in the pathogenesis of HAE flares, it was hypothesized that differential expression of the microvascular endothelial cell‐surface receptors such as g‐C1qR, cytokeratin‐1, and plasminogen activator urokinase receptor (PLAUR) could be novel biomarkers for disease activity. The gene discussed is PLAUR; the disease is hereditary angioedema.