“…C1INH also plays an important role in the regulation of other serine proteases (MASP-1, MASP-2, Factor XIIa, Factor XIa, kallikrein, plasmin, and thrombin) [Davis et al, 1986]. According to the antigenic plasma level of the C1INH protein, two types of HAE are distinguished: a quantitative defect (type I) in which the protein level is low, and a qualitative defect (type II), which is less frequent and characterized by decreased functional activity, in spite of normal or even high antigenic levels [Rosen et al, 1971]. The high incidence of de novo mutations (~25%) [Verpy et al, 1996, Pappalardo et al, 2000, and the variability of C1INH protein levels in young subjects underscore the importance of DNA assays to provide direct and rapid diagnosis for suspected HAE-cases.…”