A rarer form of HAE with normal C1-INH levels is caused by mutation of genes encoding coagulation factor XII (FXII, F12 gene) (3); further, several other causal gene variants have been identified, some plausibly associated with the kallikrein-kinin system (plasminogen PLG and kininogen KNG1) (1). This evidence concerns the gene KLK4 and hereditary angioedema.