Factor IX-R338L (Factor IX Padua) screening in a Dutch population of sibpairs with early onset venous thromboembolism

摘要

A new missense mutation in exon 8 of the F9 gene that results in a substitution of an arginine to a leucine at position 338 (R338L) was described by Simioni et al. [ 1 ]. This mutation, called factor IX Padua, was discovered in a 23 year-old man presenting with a spontaneous venous thromboembolism (VTE). Established genetic risk factors for VTE were not present in this patient. The patient had a normal factor IX antigen level but his factor IX activity level was approximately eight times the normal level. Factor IX Padua was shown to be a gain-of-function mutation resulting in an elevation of the factor IX activity. Screening for the factor IX Padua mutation in 200 controls and 200 patients with a documented VTE and normal factor IX activity levels resulted in no additional cases. Factor IX Padua was also not found in a small study including 19 VTE patients with high factor IX activity and/or high factor IX activity/antigen ratio, and 132 healthy individuals, as reported by Mazetto et al. [2].