Neonatal thrombosis and its treatment

Thromboembolic disease (TE) has been described as the new epidemic of tertiary paediatrics, and no where is this more evident than in the neonatal population. As survival of premature and sick newborns has improved, the frequency of complications associated with intensive supportive therapy and monitoring has increased. Clinically significant thrombosis is emerging as one of the more common complications associated with improved neonatal outcome. The long-term implications of neonatal thrombosis are only just being realised. This systematic review will consider the epidemiology, diagnostic strategies, and outcome for both arterial and venous TE in neonates. The role of inherited thrombophilic abnormalities, and the evidence for anticoagulation therapy will also be considered. The lack of high level evidence in determining optimum therapy is obvious. Further research regarding diagnostic strategies, and optimal therapies is urgently needed.

Biochemical activity and gene analysis of inherited protein C and antithrombin deficiency in two Chinese pedigrees

BACKGROUND

We identified the gene mutations in two Chinese pedigree of type I hereditary protein C deficiency and type I hereditary antithrombin deficiency.

METHODS

The plasma level of protein C activity (PC:A), protein C antigen (PC:Ag), protein S activity, antithrombin activity (AT:A) and antithrombin antigen (AT:Ag) of propositi and two family members were detected using ELISA and chromogenic assay, respectively. All exons and intron-exon boundaries of protein C gene and antithrombin gene were analyzed by direct sequencing of the corresponding amplified PCR products in DNA from the propositus.

RESULTS

The plasma PC:A and PC:Ag of propositus 1 was 26% and 1.43 mg/dl, respectively. The PC:Ag and PC:A of his father were normal. The decreased PC:A level was seen in his mother and 4 of his maternal pedigree. PS:A and AT:A were all normal in pedigree 1 members. A C5498T heterozygous mutation in exon 3 of protein C gene, resulting in the substitution of Arg for Trp at the 15th amino acid, was identified in propositus 1 and 8 of his relatives. The plasma AT:A and AT:Ag of propositus 2 was 48.6% and 10.4 mg/dl, respectively. The reduced AT:A and AT:Ag levels were found in his father and 5 of paternal pedigree. PC:A, PC:Ag and PS:A were all in normal range. A heterozygous 13387-9G deletion in exon 6 of antithrombin gene was identified in propositus 2. This mutation introduced a frameshift and a premature stop at codon 426 and existed in 6 members of pedigree 2.

CONCLUSION

The C5498T heterozygous mutation in exon 3 of protein C gene, first reported in China, leads to type I hereditary protein C deficiency. The 13387-9G deletion, a novel mutation, can cause antithrombin deficiency and thrombosis.

Diagnosis and treatment of a newborn with homozygous protein C deficiency

The case is reported of a seriously affected newborn with homozygous protein C deficiency who developed neonatal purpura fulminans. Foetal ultrasound at 33 wk of gestation revealed ventriculomegaly. The first lesions appeared on the scalp 48 h after birth. She was initially treated with fresh-frozen plasma and, after the diagnosis was confirmed, with purified protein C concentrate. After skin necrosis had healed, therapy was continued with oral warfarin. The infant was homozygous for protein C W380G mutation. Diagnosis at the DNA level gave the parents an option of reliable prenatal diagnosis in their subsequent pregnancy.

CONCLUSION

Difficulties in reaching an accurate diagnosis are discussed since early diagnosis and urgent therapy with protein C replacement are crucial to avoid further damage after delivery.

Protein C levels are regulated by a quantitative trait locus on chromosome 16: results from the Genetic Analysis of Idiopathic Thrombophilia (GAIT) Project

OBJECTIVE

Protein C (PC) is a component of the protein C anticoagulant pathway. PC deficiency is a risk factor associated with venous thromboembolism. As part of the Genetic Analysis of Idiopathic Thrombophilia (GAIT) Project, we conducted a genome-wide linkage scan to localize genes that influence variation in PC plasma levels.

METHODS AND RESULTS

PC levels were measured in 398 individuals belonging to 21 Spanish families. A total of 485 DNA microsatellite markers were genotyped to provide a 7.1-cM genetic map. Variance component linkage methods were used to evaluate linkage and to detect quantitative trait loci (QTL). A region on chromosome 16 (16q23), flanked by markers D16S3106 and D16S516, showed strong evidence of linkage with PC levels (LOD=3.69). This region contains 1 positional candidate gene, the NAD(P)H:dehydrogenase quinone 1 (NQO1), involved in vitamin K metabolism. The association of 1 SNP of this gene with PC levels (P=0.005) strongly supports the implication of NQO1 gene in the variability of PC levels.

CONCLUSIONS

These results illustrate the application of genomic scans to identify the genetic determinants of quantitative variation in a component of the hemostatic pathways. They provide strong evidence for a locus (QTL) on chromosome 16 that influences PC levels.

R147W mutation of PROC gene is common in venous thrombotic patients in Taiwanese Chinese

We analyzed the genetic defects of 21 unrelated patients with venous thrombosis in whom hereditary protein C deficiency was diagnosed. Eleven mutations were detected in 18 families, while no mutation was detectable in the other three families. Among these mutations, a common genetic mutation of protein C (PROC) gene recurred in 43% (nine propositi from these 21 families). This C6152T mutation at exon 7 resulted in a missense mutation, Arg147Trp (R147W). Each propositus or family carrier had another specific polymorphism T66C at exon 2, which did not change the proline at position (-21). The haplotype analysis strongly suggested a founder effect. The first thrombotic attack was significantly younger in patients with multiple genetic defects or combined with other risk factors than those without precipitating factors. We further studied the prevalence rate of R147W mutations in normal populations through PCR amplification and dot hybridization. Three different cohorts got similar results. The prevalence rate of R147W in health controls is 0.85% [95% confidence interval (CI) 0.35-1.35]. Analysis of plasma protein C levels of all patients or carriers suggested that R147W was a type II deficiency. The odds ratio of thrombosis of R147W is 5.1 (95% CI 1.7-14.8). Taken together, R147W mutation is a significant thrombotic risk factor and is the most common defect of PROC gene in Taiwanese patients with protein C deficiency. This finding is important for screening thrombophilic families in Chinese populations.

Hunting for the mutation in inherited thrombophilia

Mutation detection in inherited thrombophilia remains largely confined to the research laboratory. However, there are specific situations when investigating the genetic defect causing thrombophilia can provide additional useful clinical information. This review discusses the value of genetic analysis in the common inherited thrombophilias.

Heritability of plasma concentrations of clotting factors and measures of a prethrombotic state in a protein C-deficient family

BACKGROUND

Earlier studies found strong support for a genetic basis for regulation of coagulation factor levels and measures of a prethrombotic state (d-dimer, prothrombin fragment 1.2).

OBJECTIVES

Estimation of how much of the variation in the levels of coagulation factors and measures of a prethrombotic state, including measures of protein C activation and inactivation, could be attributed to heritability and household effect.

PATIENTS AND METHODS

Blood samples were collected from 330 members of a large kindred of French-Canadian origin with type I protein C deficiency. Heritability and common household effect were estimated for plasma concentrations of prothrombin, factor (F)V, factor VIII, factor (F)IX, fibrinogen, von Willebrand factor (VWF), antithrombin, protein C, protein S, protein Z, protein Z-dependent protease inhibitor (ZPI), fibrinopeptide A (FPA), protein C activation peptide (PCP), activated protein C-protein C inhibitor complex (APC-PCI), activated protein C-alpha1-antitrypsin complex (APC-alpha1AT), prothrombin fragment 1.2 (F1.2) and d-dimer, using the variance component method in sequential oligo-genic linkage analysis routines (SOLAR).

RESULTS

The highest heritability was found for measures of thrombin activity (PCP and FPA). High estimates were also found for prothrombin, FV, FIX, protein C, protein Z, ZPI, APC-PCI and APC-alpha1AT. An important influence of shared household effect on phenotypic variation was found for VWF, antithrombin, protein S and F1.2.

CONCLUSIONS

We found strong evidence for the heritability of single coagulation factors and measures of a prethrombotic state. Hemostatic markers with statistically significant heritability constitute potential targets for the identification of novel genes involved in the control of quantitative trait loci.

Activated protein C concentrate reverses purpura fulminans in severe genetic protein C deficiency

Severe genetic protein C deficiency is rare and is associated with severe, often fatal thrombosis. The authors report the use of recombinant activated protein C (APC) to treat an episode of purpura fulminans (PF) in a teenage girl with severe protein C deficiency who had developed anaphylaxis to fresh-frozen plasma that was given in the past to treat recurrent episodes of PF. Concomitant with an infusion of APC, 20 microg/kg/h for 10 hours, a d-dimer level that was markedly positive (6,450 ng/mL) prior to the onset of PF decreased to 847 ng/mL following the APC. The teenager was treated with heparin along with warfarin for four days until the INR was more than 3.5 and the d-dimer level was less than 230 ng/mL. At the end of the APC infusion all skin lesions of PF were resolved. There were no adverse reactions to APC. APC was safe and effective for treatment of PF in severe genetic protein C deficiency.

Late onset of clinical symptoms and recurrent ecchymotic skin lesions in a 12-year-old girl with a severe double heterozygous protein C deficiency

The authors describe a 12-year-old girl with late-onset clinical symptoms due to severe protein C deficiency. Protein C gene analysis showed double heterozygosity for two distinct mutations, associated with type I protein C deficiency. Her parents and only brother were also evaluated. Coumarin-induced skin necrosis was a recurrent feature during oral anticoagulation therapy, forcing her physicians to treat her with nadroparin (Fraxiparin) for only a few months.

Prothrombotic disorders in patients with mesenteric vein thrombosis

Mesenteric vein thrombosis (MVT) is uncommon condition. The purpose of this study was to assess prevalence of prothrombotic disorders in these patients. Eleven patients with MVT were screened for protein C, protein S, and antithrombin III deficiencies. Gene analysis was performed by polymerase chain reaction. A prothrombotic disorder was detected in 9 (81.8%) patients. Factor V Leiden, methylenetetrahydrofolate reductase TT677, and prothrombin G20210A mutations were found in 2 (18.2%), 2 (18.2%), and 5 patients (45.4%), respectively. Protein S, protein C, and antithrombin III deficiencies were present in 1, 1, and 2 patients, respectively. Four patients (36.3%) had combined defects. Thus, prothrombotic disorders may have a causative role in the pathogenesis of MVT, and these patients must be screened for these disorders.

[Type I hereditary protein C deficiency due to C5498T mutation in protein C gene]

OBJECTIVE

To identify the gene mutation in a Chinese pedigree of type I hereditary protein C deficiency.

METHODS

The plasma levels of protein C activity (PC:A), protein C antigen (PC:Ag), protein S activity, and anti-thrombin activity (AT:A) of the propositus, male, aged 7, and 11 members of the pedigree were detected using ELISA and chromogenic assay respectively. All of the nine exons and intron-exon boundaries of protein C gene of the propositus were analyzed by direct sequencing of the corresponding amplified PCR products in DNA from the propositus. Restriction enzyme site analysis was used to confirm the mutation.

RESULTS

The plasma concentrations of protein C activity and antigen of the propositus were 26% and 1.43 g/L respectively. The PC:Ag and PC:A of his father were normal. Decreased PC:A level was seen in his mother and 4 of his maternal pedigree. PS:A and AT:A were all normal in all of the pedigree members. A C5498T heterozygous mutation in exon 3, resulting in the substitution of Arg for Trp at the 15th amino acid, was identified in the propositus and 8 of his relatives. This mutation was confirmed by restriction enzyme site analysis. Mutations C/T at position 2405, A/G at position 2418, and A/T at position 2583 in the protein C promoter region were confirmed in the propositus and all members of the pedigree.

CONCLUSION

C5498T heterozygous mutation in exon 3 of protein C gene, first reported in China, leads to type I hereditary.

Protein C and protein S assessment in hospital laboratories: which strategy and what role for DNA sequencing?

This paper presents a critical assessment of protein C (PC) and protein S (PS) functional and immunological approaches with regard to DNA sequencing in a large hospital recruitment for thrombosis exploration in more than 1700 consecutive patients. After examination of clinical status and PC and PS phenotype, a genotypic study was implemented for 17 PC-deficient and 28 PS-deficient patients (activity < 70%). Sixty-five percent of the genotyped PC-deficient patients were found to have heterozygous mutations. Among the < 70% values, decreases in PC activity without gene mutation were always slight (mean value 64 +/- 7%) while patients presenting a PC gene mutation had a mean 50 +/- 17% activity (P < 0.05). Among the eight PC mutations found, only one has previously been described. A novel mutation in the promoter region (-1522), located in the HNF-1 site and associated with the Y226H heterozygous mutation, was found in a 9-month-old girl with 4% PC activity. Determination of PS functional activity was considerably improved by contemporaneous measurement of calibration and samples in a single step. Only 50% of the genotyped PS-deficient patients demonstrated heterozygous alterations of the gene. The benefit of sequencing to identify putative causal mutations was only 39% in PS-deficient women, while it was 90% in men. Among the nine PS mutations found, six have not yet been published. In the present paper, we explain our methodological choices and diagnostic strategy.

Myeloid/natural killer cell precursor acute leukemia accompanied by homozygous protein C deficiency

A patient with myeloid/natural killer (NK) cell precursor acute leukemia who was also homozygous for protein C deficiency was treated and showed a complete remission while he simultaneously received low molecular weight heparin. He presented with fever spikes, lymphadenopathy, and a bulky tumor of the anterior mediastinum. A bone marrow aspirate showed the infiltration of immature lymphoblastoid cells. The patient's diagnosis was determined to be myeloid/NK cell precursor acute leukemia by morphologic and immunophenotypic analysis (CD7(+)CD33(+)CD34(+)CD56(+)). The patient developed a thrombosis in his jugular vein on cannulation of the internal jugular vein. An examination of the serum levels and the activities of proteins C and S demonstrated a slight decrease in the protein C level but an undetectable protein C activity. The patient received the diagnosis of homozygous protein C deficiency, because both parents were found to have heterozygous protein C activity. Treatment of the patient's leukemia included induction chemotherapy (Ara-C and idarubicin) with concomitant administration of low molecular weight heparin for his homozygous protein C deficiency. He achieved a complete remission without expressing any thrombosis during the course of chemotherapy. To our knowledge, this is the first case ever described in which acute myeloid leukemia was complicated with homozygous protein C deficiency.

[Pulmonary thromboembolism associated with familial protein C deficiency type I]

A 66-year-old man was admitted to our hospital because of progressive dyspnea on effort. Arterial blood gas analysis showed severe hypoxemia, and a chest radiograph revealed reticular shadows in both lower lungs and an increase of the cardiothoracic ratio. Echocardiography demonstrated mild indentation of the interventricular septum toward the left ventricle, moderate pericardial effusion and pulmonary hypertension. From these data, we diagnosed pulmonary thromboembolism and started anticoagulation therapy. After the addition of the administration of warfarin and oxygen therapy, his symptoms disappeared. However, we could not obtain more supporting evidence of thromboembolization by methods of ventilation-perfusion scanning, digital subtraction angiography of the pulmonary artery, or venography. Blood coagulation analysis demonstrated that the patient's plasma protein C antigen levels and its activity were depleted. The patient's son had a history of thrombophlebitis and pulmonary embolization, and his data of protein C antigen levels was also decreased. Therefore, this patient was found to have a character of familial protein C deficiency type I. We could not get the conclusive proof of pulmonary thromboembolism, but we considered that the presence of familial protein C deficiency may cause exacerbation of pulmonary hypertension.

Deep vein thrombosis and acute cytomegalovirus infection: case report and review of the literature

We report the case of a 17-year-old girl with constitutional protein C deficiency who developed massive femoral vein and inferior vena cava thrombosis during the course of an acute cytomegalovirus infection. The possible role of cytomegalovirus in the pathophysiology of venous thrombosis is discussed and a review of the literature is made concerning this peculiar association.

Aggravation of endotoxin-induced disseminated intravascular coagulation and cytokine activation in heterozygous protein-C-deficient mice

In the pathogenesis of sepsis and disseminated intravascular coagulation (DIC), dysfunctional anticoagulant pathways are important. The function of the protein C system in DIC is impaired because of low levels of protein C and down-regulation of thrombomodulin. The administration of (activated) protein C results in an improved outcome in experimental and clinical studies of DIC. It is unknown whether congenital deficiencies in the protein C system are associated with more severe DIC. The aim of the present study was to investigate the effect of a heterozygous deficiency of protein C on experimental DIC in mice. Mice with single-allele targeted disruption of the protein C gene (PC+/-) mice and wild-type littermates (PC+/+) were injected with Escherichia coli endotoxin (50 mg/kg) intraperitoneally. PC+/-mice had more severe DIC, as evidenced by a greater decrease in fibrinogen level and a larger drop in platelet count. Histologic examination showed more fibrin deposition in lungs, kidneys, and liver in mice with a heterozygous deficiency of protein C. Interestingly, PC+/- mice had significantly higher levels of proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-1beta, indicating an interaction between the protein C system and the inflammatory response. Survival was lower at 12 and 24 hours after endotoxin in the PC+/- mice. These results confirm the important role of the protein C system in the coagulative-inflammatory response on endotoxemia and may suggest that congenital deficiencies in the protein C system are associated with more severe DIC and adverse outcome in sepsis.

The inherited thrombophilias: genetics, epidemiology, and laboratory evaluation

It is now possible to identify a predisposing thrombophilic condition for venous thrombosis in well over half of the cases. Certain thrombophilia diagnoses have a major impact on anticoagulant therapy, and hence it is incumbent upon physicians to understand how to diagnose and manage these conditions. This chapter covers the genetics and epidemiology of the inherited thrombophilias and provides a useful, common-sense approach to the laboratory evaluation of a patient with venous thrombosis.

Homozygous protein C deficiency with purpura fulminans: report of a new case and a description of a novel mutation

We report here a quite rare case of severe homozygous protein C deficiency. The index case is a 9-month-old Saudi boy who was born after an uneventful pregnancy at 39 weeks. The diagnosis of epidermoloysis bullosa and the appearance of scrotal haematoma raised the diagnosis of thrombosis due to protein C deficiency. The clinical presentation and extremely low level of protein C activity (< 0.01 U/ml) in the index case suggested a severe case of protein C deficiency. The father is 28 years old and the mother is 25 years old and are consanguineous. Neither had a personal or family history of thrombosis. Genomic DNA was extracted from peripheral blood of the patient and both parents, exons of protein C were amplified by polymerase chain reaction and sequenced. Sequencing revealed the presence of a novel CCTG duplicate nucleotide (effective insertion) after nucleotide 8826 in exon 9 of the protein C gene. This insertion is found in the homozygous state in the patient and in the heterozygous state in both parents. It results in a frame-shift mutation, which introduces a stop-codon, thereby generating a prematurely truncated protein. These molecular findings agree with the presence of quantitative protein C deficiency in the index case.

Guidelines for the laboratory investigation of inherited thrombophilias. Recommendations for the first level clinical laboratories

Recent advances in the laboratory diagnostic approach to inherited thrombophilia call for an update on laboratory strategies and organization. The present paper therefore deals in particular with: the panel test choice, timing and test appropriateness, and analytical methods in several clinical conditions. Specific recommendations are supported by the state-of-the-art in this branch.

Prothrombin G20210A mutation and oral contraceptive use increase upper-extremity deep vein thrombotic risk

The role played by a hypercoagulable state, either inherited or acquired, in the pathogenesis of upper-extremity deep vein thrombosis (UEDVT) remains a question of debate. We performed a case-control study including 79 patients with a first objectively confirmed episode of UEDVT, 31 secondary and 48 primary, and 165 healthy controls. Nine patients (11.4%) with UEDVT were carriers of the prothrombin G20210A mutation vs. six (3.7%) in controls; P = 0.025, OR: 3.39 (95% CI 1.16 to 9.88). No statistical difference was observed between cases and controls for the factor V Leiden mutation, AT, protein C or protein S deficiency and anticardiolipin antibodies (ACAs). Thirteen (35.1%) UEDVT patients were oral contraceptive (OC) users vs. 12 (16%) controls; P = 0.020, OR: 2.89 (95% CI 1.16-7.21). When secondary UEDVT patients were compared with controls, no differences were observed in any of the risk factors analysed. On the other hand, when primary UEDVT was considered, six (12.5%) patients were carriers of the prothrombin G20210A mutation vs. six (3.7%) controls; P = 0.031, OR: 3.76 (95% CI 1.15-12.26). Regarding ACAs, a borderline statistical significance was observed when primary UEDVT was compared with controls, P = 0.048; OR: 4.88 (95% CI 1.05-22.61). In primary UEDVT, 52% of the fertile women were OC users vs. 16% of controls; P = 0.001, OR: 5.78 (95% CI 2.13-15.67). When the interaction of both factors, i.e. prothrombin G20210A mutation and OC intake, were considered, the risk increased markedly, indicating a synergistic effect as observed with other thrombotic locations. In patients with primary UEDVT screening for antithrombin, protein C and protein S deficiency and APC resistance would not be justified, although it might be reasonable to determine the carrier status of the prothrombin G20210A mutation only in OC users.

[A point mutation of protein C gene in a congenital protein C deficiency pedigree]

OBJECTIVE

To study the phenotypes and genotypes of a protein C (PC) deficiency pedigree.

METHODS

Immunoassay (ELISA) was used for PC antigen and activated PC (APC) detection, PCR for amplification of the fragment of protein C gene exon II to exon IX, single-strand conformation polymorphism (SSCP) for difference of denatured cDNA and DNA sequencing for gene mutation.

RESULTS

Four members in the pedigree were found to be PC antigen levels between 34.3% - 67.8% and PC activity between 22% - 49% which are lower in comparison with normal references (80% - 120% and 70% - 130%, respectively). A G-to-A mutation in exon VII of the protein C gene at 6 219 position was identified in 9 members. This mutation resulted in the substitution of Arg for Gln at 169 amino acid.

CONCLUSION

The proband is of heterozygosity. The G6219 A mutation in exon VII of the protein C gene leads to the substitution of Arg 169 Gln. This mutation is reported for the first time in China.

Combined protein C and protein S deficiency in a family with repetitive thromboembolism and segregated gene mutations

A young man with repetitive deep venous thrombosis of the legs and the inferior vena cava, and his family were eventually diagnosed by means of molecular genetic analysis as having both hereditary protein C and protein S deficiency. There have been a few reports of families with combined protein C and protein S deficiency and only one report of such a family characterized at the DNA level. This was the first reported family in Japan with combined deficiency of protein C and protein S accompanied by segregation of gene lesions.

Prothrombin G20210A mutation, antithrombin, heparin cofactor II, protein C, and protein S defects

These defects are not as common as factor V Leiden, but they are more common than many other hereditary procoagulant defects. The incidence of the prothrombin gene (G20210A) mutation is not yet known with certainty, but it may approach or even exceed that of factor V Leiden. These defects also seem less common than hereditary sticky platelet syndrome; however, they are all common enough that they always should be considered in any individual with unexplained thrombosis and should be part of the work-up for patients with thrombotic disorders. Of the defects discussed herein, prothrombin G20210A mutation seems, thus far, to be more common than AT, protein C, protein S, or HC-II defects. Assessment of prothrombin gene mutation should be part of the primary evaluation of patients with unexplained thrombosis.

Familial thrombophilia is an oligogenetic disease: involvement of the prothrombin G20210A, PROC and PROS gene mutations

Population-based case-control studies and cases previously published suggest that the prothrombin G20210A mutation is a weak risk factor for thrombosis, leading to clinical expression mainly in the presence of other risk factors. We report the results of plasma and genetic analyses performed in a 13-year-old symptomatic boy homozygous for the 20210A allele and in his family, which are in accordance with this suggestion. These analyses demonstrated the presence of several PROC (R-5W, R87H) and PROS (R60C, T103N) gene mutations in this family. These additional mutations have modulating effects on clinical expression of the G20210A mutation. The present family study illustrates the concept of 'mild' mutation and the hypothesis that familial thrombophilia is a multifactorial disease.