FCM helped to categorize and reach the diagnosis in 514 patients (76.7%), while 156 (23.3%) were categorized based on other laboratory parameters (e.g., measurement of serum complement C4 and C1-inhibitor in hereditary angioedema), clinical manifestations and/or genetic testing (Supplementary Table S2). The gene discussed is SERPING1; the disease is hereditary angioedema.