Future work based on the LC-MS/MS technique applied to ex vivo generation of multiple kinin peptides by standardized stimuli (6, 34, 35) is warranted to address the physiopathology of other HAE forms with normal C1INH level, especially because the spontaneous activity of tissue kallikrein is often low in these patients (27). The gene discussed is KLK4; the disease is hereditary angioedema.