Homozygosity for R87H missense mutation and for a rare intron 7 DNA variant (7054G --> A) in the PROC genes of three siblings initially classified as heterozygotes for protein C deficiency

Compound heterozygous protein C deficiency with pulmonary embolism caused by a novel PROC gene mutation: Case report and literature review

RATIONALE

Protein C is an anticoagulation agent, and protein C deficiency results in vascular thrombosis disease. Hereditary protein C deficiency is a risk factor for pulmonary embolism in adults. Pathogenic variants of the Protein C, Inactivator Of Coagulation Factors Va And VIIIa (PROC) gene which encodes protein C have been identified as a cause of protein C deficiency.

PATIENT CONCERNS

We describe a patient with a novel mutation in the PROC gene who was diagnosed with pulmonary embolism in a Chinese family.

DIAGNOSIS

According to the results of the pulmonary computed tomography angiography (CTA) and the level of blood protein C, the patient was diagnosed with pulmonary embolism caused by protein C deficiency.

INTERVENTIONS

Whole-exome sequencing (WES) was performed for the molecular analysis.

OUTCOME

The results of patient's deoxyribonucleic acid revealed a heterozygous mutation (c.237 + 5G > A) in intron 3 of the PROC gene. His father also harbored the same mutation in the PROC gene. We also reviewed the protein C deficiencies caused by PROC gene mutations in cases.

LESSONS

A novel mutation in intron 3 of PROC gene has not been previously reported in patients with pulmonary embolism caused by protein C deficiency. After anticoagulation therapy, the patient recovered, and CT showed resolution of the thrombosis. Pulmonary embolism may be caused by protein C deficiency and the rare compound heterozygous mutation in intron 3 of the PROC gene could cause protein C deficiency via impairment of the secretory activity of protein C.

Hereditary protein C deficiency caused by the Ala267Thr mutation in the protein C gene is associated with symptomatic and asymptomatic venous thrombosis

INTRODUCTION

Protein C (PC) is a key anticoagulant that regulates hemostasis, and inherited deficiency of PC is an established risk factor for venous thrombosis (VT). The factor V Leiden mutation causing activated PC (APC) resistance is an additional risk factor for VT. Reduced PC levels in the circulation and/or APC resistance do not necessarily lead to thrombotic disease. In the present study we describe and characterize an ethnic Lebanese family in which individuals with reduced PC levels and APC resistance have various clinical symptoms.

METHODS

PC activity and antigen levels and APC resistance in the family members were quantified with commercial kits. Sequencing of PC DNA and mRNA was performed with BigDye Terminator Cycle Sequencing kit on the ABI 3730 Genetic Analyzer.

RESULTS

PC antigen and anticoagulant activity in the plasma of the proband and family members ranged from 9% to 69% and 3% to 63%, respectively, compared to levels measured in pooled normal plasma. Sequencing analysis of the PC gene of family members revealed that they were either homozygous or heterozygous for the Ala267Thr mutation. In addition, three of them exhibited APC resistance. None of the family members, except the proband, have had a history of VT despite that two of them have two genetic risk factors for thrombosis.

Continuous infusion of factor concentrates in children with haemophilia A in comparison with bolus injections

Although the concept of continuous infusion (CI) of factor concentrates is well known, prospective paediatric data are rare. We present a prospective open-labelled non-randomized study focusing on safety, efficacy and factor VIII (FVIII) usage compared with bolus injections (BI) in children. In 43 consecutive patients (0.5-17 years; median: 9.6) undergoing different operations, CI was started with an initial FVIII-bolus of 70 IU kg(-1) bodyweight, followed by a median infusion rate of 4.4 IU kg(-1) h(-1) (range: 2.8-9.5) dose adjusted for daily FVIII levels (target: 60-80%). No direct serious adverse events occurred; however, two out of 43 patients, both from the group of four patients with less than 20 exposure days (ED) before starting CI, developed a high-responding inhibitor. Two CI patients showed mild thrombophlebitis or rash. Infusion rates needed to achieve adequate FVIII levels were highly predictable and could be reduced because of decreasing FVIII clearance. Bleeding, requiring additional boli, was observed in eight out of 43 patients. Therapy duration and factor usage of CI were influenced by the procedure, but not by the product used or thrombophilia. Twelve of these CI patients were compared with 12 contemporary consecutive age- and procedure-matched BI patients. Compared with BI patients, CI patients saved 30% FVIII (812.9 vs. 563.2 IU kg(-1), P < 0.006). We conclude that CI forms a safe and effective method for perioperative care in children and reduces factor usage. Because of the unknown risk of inhibitor development, we will use CI only in patients beyond 20 ED.

In vitro evaluation of B-domain deleted recombinant factor VIII (ReFactoR) stability during simulated continuous infusion administration

The administration of factor VIII (FVIII) by continuous infusion (CI) to manage severe haemorrhage or during major surgery appears pharmacokinetically and economically favourable when compared with intermittent bolus infusions. Successful clinical use of FVIII delivered by CI, however, requires a thorough assessment of product stability under conditions encountered during CI such as prolonged exposure to the delivery devices at ambient temperature and the low FVIII concentrations. This investigation has identified conditions under which ReFacto, a recombinant human B-domain deleted FVIII, can be successfully delivered under dilute conditions when using large volume parenteral polyvinyl chloride (PVC) bags without the addition of stabilizers or as an undiluted preparation delivered by ambulatory infusion pumps. ReFacto is stable for 36 h when stored in large volume parenteral PVC reservoirs at 3 and 8 IU mL(-1) or 72 h when delivered undiluted at 62 IU mL(-1) by CADD infusion pumps. The greatest concern with the delivery of ReFacto by CI is adsorptive losses to the contact surfaces of the delivery system. There was no significant binding of ReFacto to the PVC reservoirs overtime; however, there was appreciable binding to the administration set under certain conditions. The binding was influenced by the ionic strength of the solution, residence time in the tubing and protein concentration. The recovery and stability profile of ReFacto under certain conditions appears favourable when compared with that of full-length recombinant FVIII products, observed by other investigators.

Continuous infusion of coagulation factor products

OBJECTIVE

To review clinical information related to the use of continuous infusion factor products in patients with hemophilia. Specifically, case reports and open-label trials are summarized involving the use of factor VIII and recombinant factor VIIa for a variety of indications including surgical prophylaxis, acute bleeding, primary prevention, and management of inhibitors. In addition, issues surrounding the use of continuous infusion of factor products such as pharmacokinetic rationale, stability/sterility, and cost are reviewed.

DATA SOURCES

Primary and review articles were identified through a MEDLINE search (1990-June 2001) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated, and all information deemed relevant was included in this review.

DATA SYNTHESIS

Data concerning the administration of factor products are primarily detailed in open-label trials and case reports. Comparisons between intermittent bolus injections and continuous infusion of factor products are limited and primarily compare continuous infusion regimens with historical controls. The rationale behind the continuous-infusion approach is linked to the pharmacokinetics of factor products administered via this route. Pharmacokinetic data reveal that, with continuous infusion of factor products, a reduction in clearance and a maintenance of factor serum concentrations are noted.

CONCLUSIONS

Administration of factor products (factor VIII and recombinant factor VIIa) via continuous infusion has produced favorable hemostatic effects compared with intermittent bolus injections. The advantages of continuous infusion include maintenance of a constant factor concentration, thereby reducing risk of bleeding from excessively low trough concentrations, and a decrease in factor consumption related to a reduction in factor clearance with constant infusion. Manufacturers recommend using reconstituted factor products either immediately or within 1-3 hours after reconstitution; however, several studies have found the products to be stable and sterile for longer periods.