There are two distinct groups of BK-AE: BK-AE with C1-INH deficiency, which is further divided into acquired (AAE-C1-INH) and hereditary (HAE); and BK-AE without C1-INH deficiency, which includes hereditary (mutations in the F12 or PLG genes), drug-induced, and non-mast-cell-mediated BK-AE [15]. The gene discussed is SERPING1; the disease is acrodermatitis enteropathica.