[Clinical phenotype and gene mutation analysis of 12 patients with hereditary protein C deficiency in different families].

Objective: To investigate the molecular pathogenesis and clinical features of unrelated 12 patients with inherited coagulation protein C (PC) deficiency in Chinese population. Methods: The PC activity (PC:A) and PC antigen (PC:Ag) were detected by chromogenic substrate and enzyme linked immunosorbent assay, respectively. The nine exons and flanking sequences of the protein C (PROC) gene were amplified by polymerase chain reaction with direct sequencing, and the suspected mutations were validated by reverse sequencing (clone sequencing for deletion mutations) . Results: The PC:A of the 12 probands decreased significantly, ranging from 18% to 55%, and the PC:Ag of the 10 probands decreased significantly. Eleven mutations were found, out of which four mutations [c.383G>A (p.Gly128Asp) , c.997G>A (p.Ala291Thr) , c.1318C>T (p.Arg398Cys) , and c.532G>C (p.Leu278Pro) ] were discovered for the first time. Six mutations were in the serine protease domain, four mutations were located in epidermal growth factor (EGF) -like domains, and one mutation was located in activation peptide. There were two deletion mutations (p.Met364Trp fsX15 and p.Lys192del) , and the rest were missense mutations. Mutations p.Phe181Val and p.Arg189Trp were identified in three unrelated families. All mutations may be inherited, and consanguineous marriages were reported in two families. Among the probands, nine cases had venous thrombosis, two cases had poor pregnancy manifestations, and one case had purpura. Conclusion: Patients with PC deficiency caused by PROC gene defects are prone to venous thrombosis, especially when there are other thrombotic factors present at the same time.目的： 探讨来自不同家系12例遗传性蛋白C（PC）缺陷症先证者的基因突变类型与临床特征。 方法： 采用发色底物法检测血浆PC活性，酶联免疫吸附法检测PC抗原含量。采用PCR直接测序法分析先证者PROC基因9个外显子及其侧翼序列，对发现的疑似突变用反向（缺失突变用克隆）测序予以验证。 结果： 12例先证者的PC活性均明显下降（18%~55%），其中10例先证者的PC抗原水平显著降低（13%~58%）。共发现11种PROC基因突变，其中c.383G>A（p.Gly128Asp）、c.997G>A（p.Ala291Thr）、c.1318C>T（p.Arg398Cys）和c.532G>C（p.Leu278Pro）4种杂合突变为首次发现；6种突变发生在丝氨酸蛋白酶结构域、4种发生在表皮生长因子同源区域（EGF）、1种突变在EGF和丝氨酸蛋白酶结构域之间的激活肽区域；缺失突变（p.Met364Trp fsX15和p.Lys192del）2种，其余为错义突变。有3例无亲缘关系的先证者检出p.Phe181Val和p.Arg189Trp纯合或杂合突变。所有基因突变可能来自先证者的父亲和（或）母亲，其中2个家系存在近亲婚配。先证者有9例出现静脉血栓形成、2例有不良妊娠表现、1例出现紫癜。 结论： PROC基因缺陷导致的PC缺陷症患者易发生静脉血栓形成，尤其当同时存在其他易栓因素时。.