Clinical phenotype and gene mutation analysis of 12 patients with hereditary protein C deficiency in different families / 中华血液学杂志

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.

Diagnosis of Severe Protein C Deficiency Confirmed by Presence of Rare PROC Gene Mutation

Protein C (PROC) deficiency is caused by mutations in the PROC gene on chromosome 2q14.3. Patients with PROC deficiency typically present distinguished purpura, intracerebral and intravascular coagulopathy, and ophthalmologic complications. Here, we report a rare severe form of PROC deficiency resulting from a compound heterozygosity in PROC. The patient was a 5-day-old female neonate born at 39 weeks of gestation with a birth weight of 2,960 g. She was transferred to our hospital with running a fever at 38.5℃ and with dark red patches on her feet. At admission, a complete blood count showed no specific findings, but levels of PROC and protein S were abnormally low (1% and 68%, respectively). Magnetic resonance imaging revealed intracerebral hemorrhaging and parenchymal damage with dysplasia of the brain. Ophthalmologic examination revealed vitreous hemorrhaging with retinal detachment. Genetic testing revealed a missense mutation (Arg211Trp) and a frameshift mutation (Gly239Serfs*8) in PROC, inherited from the father and mother, respectively. The patient recovered from purpura after undergoing ventriculoperitoneal shunting and treatment with fresh frozen plasma, warfarin sodium, and PROC concentrate. This is the first report of severe neonatal PROC deficiency with purpura fulminans, vitreous hemorrhage, and intracerebral hemorrhage confirmed via PROC genetic testing, which identified a rare compound heterozygosity of PROC.

A Novel Silent Substitution (C8516T) in Exon 9 of the Human PROC Gene

Protein C is a vitamin K dependent serine protease zymogen, which has a regulatory influence over the coagulation cascade via the inhibition of factors Va and VIIIa. Hereditary protein C deficiency is associated with an increased risk of thromboembolic disease. A multitude of families displaying protein C (PROC) gene defects have been reported, and a number of DNA sequence polymorphisms are known to occur in the PROC gene. We have identified a previously undescribed silent substitution (C8516T) by direct DNA sequencing in a Korean patient with thrombosis and protein C deficiency. In addition, a rare T allelic frequency (0.016) was determined in 123 patients with acquired or hereditary protein C deficiency.