The clinical and genetic landscape of early-onset thrombophilia in Japan

OBJECTIVES

To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan.

METHODS/RESULTS

Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019).

CONCLUSIONS

We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

Analysis of PROS1 mutations and clinical characteristics in three Chinese families with hereditary protein S deficiency

We report three heterozygous PROS1 mutations that caused type I protein S deficiency in three unrelated Chinese families. We measured protein S activity and antigen levels for all participants, screened them for mutations in the PROS1 gene. And we employed the calibrated automated thrombin generation (CAT) method to investigate thrombin generation. Numerous bioinformatics tools were utilized to analyze the conservation, pathogenicity of mutation, and spatial structure of the protein S. Phenotyping analysis indicated that all three probands exhibited simultaneous reduced levels of PS:A, TPS:Ag, and FPS:Ag. Genetic testing revealed that proband A harbored a heterozygous c.458_458delA (p.Lys153Serfs*6) mutation in exon 5, proband B carried a heterozygous c.1687C>T (p.Gln563stop) mutation in exon 14, and proband C exhibited a heterozygous c.200A>C (p.Glu67Ala) mutation in exon 2. Bioinformatic analysis predicted that the p.Lys153Serfs*6 frameshift mutation and the p.Gln563stop nonsense mutation in the protein S were classified as "disease-causing." The identification of the novel mutation p.Lys153Serfs*6 in PROS1 enriches the Human Genome Database. Our research suggests that these three mutations (p.Lys153Serfs*6, p.Gln563stop, and p.Glu67Ala) are possibly responsible for the decreased level of protein S in the three families. Furthermore, the evidence also supports the notion that individuals who are asymptomatic but have a family history of PSD can benefit from genetic analysis of the PROS1 gene.

A Rare Case with Pulmonary Embolism and Literature Review

BACKGROUND

Pulmonary embolism is rare in children, and most of them have high-risk factors, such as antiphospholipid syndrome, intravenous catheterization, fracture bed rest, etc. For children with pulmonary embolism without clear inducement, hereditary thrombophilia should be considered. Genetic protein S deficiency (PSD) is a kind of thrombophilia, which is caused by the mutation of PROS 1 gene, resulting in an increased tendency to thrombosis.

METHODS

The diagnosis of the two cases was made after detecting based on Thrombophilia screening and Sanger sequencing in clinical laboratory.

RESULTS

Sanger sequencing found that case 2 and case 1 genotypes were the same, case 1 sister and grandfather carried c.200a>c (p.e67a) mutation, and case 1 aunt and grandmother did not carry PROS1 gene mutation. Case 1 received anticoagulation therapy for 3 months, and case 2 also received anticoagulation therapy for 3 months. During the 1 year follow-up, no new thrombotic events and no adverse reactions such as bleeding were observed in both patients.

CONCLUSIONS

For children with pulmonary embolism without clear risk factors, PSD should be considered, and protein S activity should be tested before receiving anticoagulant drugs.

Evaluation of Optimal Sample Processing Conditions for Accurate Measurement of Protein S Activity

OBJECTIVE

Protein S(PS) activity, especially PS-specific activity calculated by total PS activity (tPSAct) divided by total PS antigen (tPSAg), is important in the diagnosis of hereditary PS deficiency (PSD). The cleavage of PS at a thrombin-sensitive region (TSR) by proteases reduces the anticoagulant activity of PS. Therefore, we investigated the effect of sample processing and storage on tPSAct and PS cleavage.

METHODS

Blood samples were collected from ten healthy subjects, and tPSAg and tPSAct were measured in whole blood or plasma stored at room temperature (RT) or 4°C. The cleaved PS was detected by western blotting, and the relationship between decreases in PS-specific activity and increase rates of cleaved PS was evaluated. Furthermore, the stability of tPSAg and tPSAct on the long-term storage of plasma was also evaluated.

RESULTS

Both whole blood and plasma stored at RT and whole blood stored at 4°C showed decreased tPSAct (50-80%) after 24 hours (P<0.05). PS-specific activity levels negatively correlated with the increase rate of cleaved PS (r =-0.84, P<0.001). The tPSAct was decreased to 60% after three days in plasma stored at 4°C (P<0.05) but was stable for about one month when stored at -20°C or below.

CONCLUSION

Inappropriate processing and storage result in falsely low PS-specific activity due to the cleavage of PS in the blood collection tubes, which may lead to misdiagnosis of PSD. Samples should be centrifuged immediately after collection, and the plasma should be frozen.

Recommendations for clinical laboratory testing for protein S deficiency: Communication from the SSC committee plasma coagulation inhibitors of the ISTH

Hereditary deficiencies of protein S (PS) increase the risk of venous thrombosis; however, assessing the plasma levels of PS can be difficult because of its complex physiological interactions in plasma, sample-related preanalytical variables, and numerous acquired disease processes. Reliable laboratory assays are essential for accurate evaluation of PS when diagnosing a congenital deficiency based on the plasma phenotype alone. This report presents the current evidence-based recommendations for clinical PS assays as well as when to test for PS abnormalities.

Two Novel Variants in the Protein S Gene PROS1 Are Associated with Protein S Deficiency and Thrombophilia

Protein S (PS) is an important anticoagulant. Its main function is to act as a non-enzymatical cofactor of activated protein C. PS deficiency is defined as low plasma levels of PS and/or loss of function associated with variable risk of venous thromboembolism (VTE). We report 2 novel variants in the PS gene (PROS1) which are associated with PS deficiency and severe thrombophilic diathesis in 2 patients. Patient 1 suffered from 3 VTE events, including a spontaneous VTE at the age of 19. Patient 2 suffered from 2 provoked VTE events. In both patients decreased plasma levels of PS antigen as well as decreased PS activity were found. Gene sequencing results showed a heterozygous deletion of 8 base pairs (c.938_945delTAAAATTT, p.Leu313Serfs13*) in exon 9 of the PROS1 gene in patient 1 and a missense variant (c.1613C>T, p.Ser538Phe) in patient 2. Due to the clinically proven history of recurrent VTE events in both patients, genetic testing of first-degree relatives is discussed.

New functional test for the TFPIα cofactor activity of Protein S working in synergy with FV-Short

Essentials Protein S and FV-Short are synergistic cofactors to Tissue Factor Pathway Inhibitor α (TFPIα). An assay for the TFPIα synergistic cofactor activity of protein S with FV-Short was developed. The assay was specific for the synergistic TFPIα-cofactor activity of free protein S. Protein S deficient individuals with known mutations were correctly distinguished from controls. SUMMARY: Background Protein S is an anticoagulant cofactor to both activated protein C and tissue factor pathway inhibitor (TFPIα). The TFPIα-cofactor activity of protein S is stimulated by a short isoform of factor V (FV-Short), the two proteins functioning in synergy. Objective Using the synergistic TFPIα-cofactor activity between protein S and FV-Short to develop a functional test for plasma protein S. Patients/Methods TFPIα-mediated inhibition of FXa in the presence of FV-Short, protein S and negatively charged phospholipid vesicles was monitored in time by synthetic substrate S2765. TFPIα, FXa and FV-Short were purified proteins, whereas diluted plasma from protein S deficient patients or controls were used as source for protein S. Results The assay was specific for free protein S demonstrating good correlation to free protein S plasma levels (r = 0.92) with a Y-axis intercept of -5%. Correlation to concentrations of total protein S (free and C4BPβ+-bound) was lower (r = 0.88) and the Y-axis intercept was +46%, which is consistent with the specificity for free protein S. The test distinguished protein S-deficient individuals from 6 families with known ProS1 mutations from family members having no mutation. Protein S levels of warfarin-treated protein S deficient cases were lower than protein S in cases treated with warfarin for other causes. Conclusions We describe a new assay measuring the TFPIα-cofactor activity of plasma protein S. The test identifies type I/III protein S deficiencies and will be a useful tool to detect type II protein S deficiency having defective TFPIα-cofactor activity.

Recurrent pulmonary embolism associated with deep venous thrombosis diagnosed as protein s deficiency owing to a novel mutation in PROS1: A case report

RATIONALE

Protein S (PS) deficiency that can be inherited or acquired is an independent risk factor for venous thromboembolism (VTE).

PATIENT CONCERNS

In this report, we present a case of recurrent pulmonary embolism (PE) and deep venous thrombosis (DVT) due to PS deficiency.

DIAGNOSES

A 32-year-old male patient with significant decrease in PS activity was detected by laboratory tests. Genetic examination of the PROS1 gene showed a transition of G to T in exon 14 (c.1792 G>T, p.E598X), which was a paternal inherited heterozygous G1792T substitution in the laminin G-type repeat domain, generating a premature stop codon at Glu598.

INTERVENTIONS

We considered that the inherited PS deficiency due to a PROS1 gene mutation may associate with recurrent VTE. The patient was suggested to have an extended anticoagulant therapy to avoid a severe VTE event.

OUTCOMES

The patient was discharged home with continued oral anticoagulants and was still seen in clinic for follow-up.

LESSONS

It is necessary for the young patient with recurrent idiopathic thrombosis to perform an inherited PS deficiency test and receive anticoagulant therapy for an extended period.

The prevalence and clinical manifestation of hereditary thrombophilia in Korean patients with unprovoked venous thromboembolisms

Background

Hereditary thrombophilia (HT) is a genetic predisposition to thrombosis. Asian mutation spectrum of HT is different from Western ones. We investigated the incidence and clinical characteristics of HT in Korean patients with unprovoked venous thromboembolism (VTE).

Methods

Among 369 consecutive patients with thromboembolic event who underwent thrombophilia tests, we enrolled 222 patients diagnosed with unprovoked VTE. The presence of HT was confirmed by DNA sequencing of the genes that cause deficits in natural anticoagulants (NAs). Median follow-up duration was 40±38 months.

Results

Among the 222 patients with unprovoked VTE, 66 (29.7%) demonstrated decreased NA level, and 33 (14.9%) were finally confirmed to have HT in a genetic molecular test. Antithrombin III deficiency (6.3%) was most frequently detected, followed by protein C deficiency (5.4%), protein S deficiency (1.8%), and dysplasminogenemia (1.4%). The HT group was significantly younger (37 [32–50] vs. 52 [43–65] years; P < 0.001) and had a higher proportion of male (69.7% vs. 47%; P = 0.013), more previous VTE events (57.6% vs. 31.7%; P = 0.004), and a greater family history of VTE (43.8% vs. 1.9%; P < 0.001) than the non-HT group. Age <45 years and a family history of VTE were independent predictors for unprovoked VTE with HT (odds ratio, 9.435 [2.45–36.35]; P = 0.001 and 92.667 [14.95–574.29]; P < 0.001).

Conclusions

About 15% of patients with unprovoked VTE had HT. A positive family history of VTE and age <45 years were independent predictors for unprovoked VTE caused by HT.

New functional assays to selectively quantify the activated protein C- and tissue factor pathway inhibitor-cofactor activities of protein S in plasma

Essentials Protein S is a cofactor of activated protein C (APC) and tissue factor pathway inhibitor (TFPI). There are no assays to quantify separate APC and TFPI cofactor activities of protein S in plasma. We developed assays to measure the APC- and TFPI-cofactor activities of protein S in plasma. The assays were sensitive to protein S deficiency, and not affected by the Factor V Leiden mutation.

SUMMARY

Background Protein S plays an important role in the down-regulation of coagulation as cofactor for activated protein C (APC) and tissue factor pathway inhibitor (TFPI). Aim To develop functional assays to quantify the APC- and TFPI-cofactor activities of protein S in plasma. Methods APC- and TFPI-cofactor activities of protein S in plasma were measured using calibrated automated thrombography in protein S-depleted plasma supplemented with a small amount of sample plasma either in the presence of anti-TFPI antibodies and APC (APC-cofactor activity) or at excess full-length TFPI without APC (TFPI-cofactor activity). Total and free protein S levels in plasma were measured by ELISAs. Results Average APC-cofactor activities of protein S were 113%, 108% and 89% in plasma from normal individuals (n = 15), FV Leiden heterozygotes (n = 14) and FV Leiden homozygotes (n = 7), respectively, whereas the average APC-cofactor activity of protein S in plasma from heterozygous protein S-deficient individuals (n = 21) was significantly lower (55%). Similar trends were observed for the TFPI-cofactor activity of protein S, with averages of 109%, 115% and 124% in plasma from individuals with normal protein S levels and different FV Leiden genotypes, and 64% in plasma from protein S-deficient patients. APC-cofactor activities of protein S correlated significantly with free and total protein S antigen levels, whereas TFPI-cofactor activities correlated less with protein S antigen levels. Conclusion We have developed functional protein S assays that measure both the APC- and TFPI-cofactor activities of protein S in plasma, which are hardly if at all affected by the FV Leiden mutation.

Risk factors associated with provoked pulmonary embolism

BACKGROUND/AIMS

This study aimed to investigate the risk factors associated with provoked pulmonary embolism (PE).

METHODS

This retrospective cohort study included 237 patients with PE. Patients that had transient risk factors at diagnosis were classified as having provoked PE, with the remaining patients being classified as having unprovoked PE. The baseline clinical characteristics and factors associated with coagulation were compared. We evaluated the risk factors associated with provoked PE.

RESULTS

Of the 237 PE patients, 73 (30.8%) had provoked PE. The rate of respiratory failure and infection, as well as the disseminated intravascular coagulation score and ratio of right ventricular diameter to left ventricular diameter were significantly higher in patients with provoked PE than in those with unprovoked PE. The protein and activity levels associated with coagulation, including protein C antigen, protein S antigen, protein S activity, anti-thrombin III antigen, and factor VIII, were significantly lower in patients with provoked PE than in those with unprovoked PE. Multivariate analysis showed that infection (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4 to 7.4) and protein S activity (OR, 0.97; 95% CI, 0.95 to 0.99) were significantly associated with provoked PE.

CONCLUSIONS

Protein S activity and presence of infection were important factors associated with provoked PE. We should pay attention to the presence of infection in patients with provoked PE.

Genetic Risk Factors in Venous Thromboembolism

Genetic risk factors predispose to thrombophilia and play the most important etiopathogenic role in venous thromboembolism (VTE) in people younger than 50 years old. At least one inherited risk factor could be found in about half of the cases with a first episode of idiopathic VTE.Roughly, genetic risk factors are classified into two main categories: loss of function mutations (such as deficiencies of antithrombin, protein C, protein S) and gain of function mutations, (such as prothrombin mutation G20210A, factor V Leiden). A revolutionary contribution to the genetic background of VTE was brought by the achievements of the genome-wide association studies which analyze the association of a huge number of polymorphisms in large sample size.Hereditary thrombophilia testing should be done only in selected cases. The detection of hereditary thrombophilia has impact on the management of the anticoagulation in children with purpura fulminans, pregnant women at risk of VTE and may be useful in the assessment of the risk for recurrent thrombosis in patients presenting an episode of VTE at a young age (<40 years) and in cases with positive family history regarding thrombosis.

Protein C and protein S deficiency - practical diagnostic issues

Protein C (PC) and protein S (PS) are vitamin K-dependent glycoproteins, that act as natural anticoagulants. The proteolytic activation of PC by thrombin occurs on the surface of endothelial cells and involves thrombomodulin and endothelial PC receptor. In the presence of PS, phospholipids and calcium, activated PC (APC) inactivates membrane bound factors V (FVa) and FVIIIa by their cleavage at the specific arginine residues. PC and PS deficiencies are inherited as autosomal dominant disorders associated with recurrent venous thromboembolism (VTE) and, in most cases, derived from heterozygous missense mutations (78% and 63%, respectively). Heterozygous PC deficiency is found in 6% of families with inherited thrombophilia, in 3% of patients with a first-time deep vein thrombosis (DVT) and 0.2-0.3% of healthy individuals. The PS deficiency is detected more commonly than PC deficiency and its prevalence has been estimated with a less than 0.5% in the general European population and 2% to 12% of selected groups of thrombophilic patients. Approximately 75% of PC-deficient patients have type I deficiency and 95% of PS-deficient patients develop type I and type III of PS deficiency. The diagnosis of PC and PS deficiencies is challenging, many preanalytical and analytical factors may affect the PC/PS levels. Molecular analysis of the PC and PS genes (PROC and PROS1, respectively) involves direct gene sequencing and if negative, multiplex ligation-dependent probe amplification (MLPA) method. Patients with low PC and PS levels and the known mutation within PROC or PROS1 genes combined with other genetic or environmental thrombosis factors are at increased risk of recurrent thromboembolic events and require lifelong oral anticoagulation.

Protein S

Protein S (PS) is a vitamin K-dependent plasma glycoprotein. Around 60-70% of PS in plasma is noncovalently bound to C4-binding protein (C4BP). Free PS functions as a cofactor that enhances the activity of activated protein C (APC) in the proteolytic degradation of activated factors V and VIII. PS also has a more recently described APC-independent ability to directly inhibit prothrombinase and tenase by direct binding of activated factors V, VIII, and X. Given that PS is one of the major naturally occurring inhibitors of coagulation, acquired or hereditary deficiencies of this protein result in excessive thrombin generation. As a vast array of mutations are responsible for hereditary PS deficiencies, screening for their presence by DNA testing would require sequencing each entire gene involving numerous exons. Moreover, the knowledge of the gene mutation does not offer any benefit in the treatment of thrombophilic families, so the routine molecular characterization is not indicative. These defects are detected by functional or immunological assays for free and total PS forms. Given that functional PS assays may detect some forms of PS deficiency that free PS immunoassays may miss, it is recommended to include them for initial testing along with immunoassays for free PS, although they should be used with caution. Functional PS assays are subject to multiple interference. For example in the presence of lupus anticoagulant (LA), only free PS immunoassays are recommended for initial testing. PS antigen assays are more popular with most laboratories.

[Thrombosis of the superior vena cava revealing a protein S deficiency]

Thrombosis of the superior vena cava is attached to several causes including deficiency of the protein S. It occurs gradually by a superior vena cava syndrome. We report a patient aged 22 years, no toxic habits or bipolar aphthosis, which presented for 3 months a superior vena cava syndrome. The radiological and biological assessments confirmed thrombosis of the superior vena cava and a deficit of the protein S for which the patient was put under anticoagulant therapy with good clinical and radiological improvement. Through this observation, the authors report a rare cause of thrombosis of the superior vena cava which is the isolated protein S deficiency and provide a review of the literature.

Implantation of left ventricular assist device complicated by undiagnosed thrombophilia

A patient with dilated cardiomyopathy and no history of thromboembolic events received a surgically implanted axial-flow left ventricular assist device. After implantation, transesophageal echocardiography revealed a giant thrombus on the lateral and anterior aspects of the left ventricle. The inflow cannula inserted through the apex of the left ventricle was not obstructed, and the device generated satisfactory blood flow. Laboratory screening for thrombophilia showed protein S deficiency, heterozygous factor V Leiden mutation, and heterozygous MTHFR C667T mutation. During the entire duration of circulatory support, no significant suction events were detected, and the patient was listed for heart transplantation. Ventricular assist device implantation can unmask previously undiagnosed thrombophilia; therefore, it should be necessary to identify thrombophilic patients before cardiac support implantation.

Deep vein thrombosis associated with protein C and protein S deficiency: an unusual cause of acute abdomen

Deep venous thrombosis is an extremely rare cause of acute abdomen and is often difficult to diagnose. Protein C and protein S deficiencies are rare genetic abnormalities that predispose the patient to thrombophilia and lead to thrombosis. We report the case of a previously healthy 7-year-old boy with iliofemoral thrombosis due to protein C and protein S deficiencies mimicking acute abdomen.

Protein S abnormalities: a diagnostic nightmare

Heterozygous deficiency of Protein S (PS) increases the risk for developing thrombosis. Many acquired conditions alter plasma PS levels. These complex interactions of PS in plasma make it imperative that clinical PS assay limitations are understood so that the assays are reliable, reproducible and specific to diagnose true genetic abnormalities based on plasma phenotype alone. Unfortunately, the diagnosis of PS deficiency is difficult and complicated. Three basic assays can be utilized for assessing PS in plasma: PS activity assay, Free PS antigen assay, and Total PS antigen assay. This article will review these clinical assays and their associated problems. We also discuss the confounding and interfering factors that make it difficult to obtain an accurate diagnosis of PS deficiency.

[Genetic diagnostics of pathogenic splicing abnormalities in the clinical laboratory--pitfalls and screening approaches]

In recent years, genetic diagnostics of pathogenic splicing abnormalities are increasingly recognized as critically important in the clinical genetic diagnostics. It is reported that approximately 10% of pathogenic mutations causing human inherited diseases are splicing mutations. Nonetheless, it is still difficult to identify splicing abnormalities in routine genetic diagnostic settings. Here, we studied two different kinds of cases with splicing abnormalities. The first case is a protein S deficiency. Nucleotide analyses revealed that the proband had a previously reported G to C substitution in the invariant AG dinucleotide at the splicing acceptor site of intronl/exon2, which produces multiple splicing abnormalities resulting in protein S deficiency. The second case is an antithrombin (AT) deficiency. This proband had a previously reported G to A substitution, at nucleotide position 9788 in intron 4, 14 bp in front of exon 5, which created a de novo exon 5 splice site and resulted in AT deficiency. From a practical standpoint, we discussed the pitfalls, attentions, and screening approaches in genetic diagnostics of pathogenic splicing abnormalities. Due to the difficulty with full-length sequence analysis of introns, and the lack of RNA samples, splicing mutations may escape identification. Although current genetic testing remains to be improved, to screen for splicing abnormalities more efficiently, it is significant to use an appropriate combination of various approaches such as DNA and/or RNA samples, splicing mutation databases, bioinformatic tools to detect splice sites and cis-regulatory elements, and in vitro and/or in vivo experimentally methods as needed.

Thrombin generation-based assays to measure the activity of the TFPI-protein S pathway in plasma from normal and protein S-deficient individuals

BACKGROUND

Protein S acts as a cofactor for full-length tissue factor pathway inhibitor (TFPI) in the downregulation of thrombin formation.

OBJECTIVE

To develop a functional test to measure the activity of the TFPI-protein S system in plasma.

METHODS/PATIENTS

Using calibrated automated thrombography, we quantified the activity of the TFPI-protein S system in plasma by measuring thrombin generation in the absence and presence of neutralizing antibodies against protein S or TFPI. Moreover, we designed an enzyme-linked immunosorbent assay (ELISA) to determine the level of full-length TFPI in plasma. The performance of these assays was examined in plasma from 85 normal individuals and from 35 members of protein S-deficient families.

RESULTS

The ratio of thrombin peaks determined in the absence and presence of anti-protein S antibodies (protein S ratio = 0.5 in normal plasma) is a measure of the TFPI cofactor activity of protein S, whereas the ratio of thrombin peaks determined in the absence and presence of anti-TFPI antibodies (TFPI ratio = 0.25 in normal plasma) is a measure of the overall activity of the TFPI-protein S system. Protein S and TFPI ratios were elevated in protein S-deficient individuals, indicating an impairment of the TFPI-protein S system. Both ratios correlated well with full-length TFPI levels, which were significantly lower in protein S-deficient patients than in normal family members.

CONCLUSIONS

Functional assays for the TFPI-protein S system and an ELISA for full-length TFPI were developed. These assays show that the activity of the TFPI-protein S anticoagulant pathway is impaired in individuals with congenital protein S deficiency.

Unraveling the thrombophilia paradox: from hypercoagulability to the prothrombotic state

The thrombophilia paradox whereby thrombophilia testing identifies defects associated with an increased risk of a first venous thrombosis but not of a particularly high risk of recurrence is likely the result of limitations imposed by a limited dichotomous testing strategy compounded by test inaccuracy and imprecision. Consequently, the observed intermediate phenotype (defined by limited laboratory test results) is not fully concordant with the heritable genotype. The next generation of thrombophilia tests, which utilize either individual genomic analysis or global measurement of the composite plasma intermediate phenotype, may more accurately quantify the thrombophilic risk. In conjunction with clinical risk assessment a more quantitative measurement of hypercoagulability and definition of the prothrombotic state should facilitate transition of clinical management from a disease-focused to a more patient-focused strategy.

[Congenital protein S deficiencies; diagnostic difficulties]

Protein S is a physiologic inhibitor of coagulation acting as a cofactor of activated protein C (APC) that inhibits factor Va and VIII. Approximately 60% of PS is bound to C4bBP, a protein of the complement system and only the free PS has a cofactor PCa role. Congenital PS deficiencies are diagnosed by immunologic dosage of free and total PS and functional assay evaluating APC cofactor activity. However, it has been demonstrated a direct anticoagulant activity of free PS, non-dependant of APC on the cascade coagulation and even PS bound to C4bBP seems to have anticoagulant properties. So, it appears that functional assays available estimate only a part of PS anticoagulant activities and, in addition, many interferences are reported with these tests (lupus anticoagulant, factor V Leiden, factor VIII excess...). Immunologic dosages are more reliable in spite of rare qualitative PS deficiencies that could be non-diagnosed. PS deficiencies are often difficult to diagnose because of an overlapping between normal and pathological values. Familial studies are necessary to prove the hereditary origin because there are several causes of acquired and sometimes persistent PS deficiencies (liver insufficiency, vitamin K absence, hormonal therapy in women, PS auto immune deficiency). About 200 different mutations were retrieved and, therefore, molecular studies are not of current practice. It is recommended currently to measure in first intention the free PS, if possible in association with PCa cofactor activity.

Bilateral pulmonary artery aneurysms with protein C and protein S deficiency in a patient with Behçet's disease

Behçet's disease is a chronic inflammatory disorder of unknown aetiology, characterized by recurrent attacks. Pulmonary artery aneurysm is a rare but serious complication of Behçet's disease. We describe a patient with Behçet's disease and protein C and S deficiency who developed bilateral pulmonary artery aneurysms.

[Anesthetic management of cesarean section in a patient with pulmonary embolism due to protein S deficiency diagnosed postoperatively]

A 27-year-old pregnant woman with pulmonary embolism was scheduled for cesarean section. She received anticoagulant therapy with continuous infusion of heparin and prophylactic placement of an inferior vena cava (IVC) filter. Heparin was discontinued 7 hours before operation. Spinal anesthesia using hyperbaric bupivacaine 12 mg was performed and the operation was completed uneventfully. She was given a diagnosis of protein S deficiency after discharge. Preoperative anticoagulant therapy and placement of IVC filter may be effective in preventing new pulmonary embolism.

Protein S deficiency and lower-extremity arterial thrombosis: complicating a common presentation

A 42-year-old woman presented to the emergency department with progressive painful discoloration of the digits of her right foot and symptoms previously diagnosed as neuroma. She was admitted to the hospital for dorsalis pedis arterial occlusion and ischemic foot pain. Despite attempts to restore perfusion to the right leg, ischemia of the right foot persisted and progressed to digital gangrene. The patient subsequently required right transmetatarsal amputation and eventually below-the-knee amputation. After extensive inpatient vascular and hematologic work-up of this otherwise healthy woman, test results revealed that she had protein S deficiency, hepatitis C, and human immunodeficiency virus type 1. In addition to describing this patient's evaluation and treatment, we review protein S deficiency, including its correlation with human immunodeficiency virus type 1 infection and laboratory diagnosis. This case promotes awareness of protein S deficiency and serves as a reminder to the physician treating patients with vascular compromise and a history of human immunodeficiency virus type 1 to include protein S deficiency in the differential diagnosis.

Use of a functional assay to diagnose protein S deficiency; inappropriate testing yields equivocal results

Inherited deficiency of protein S (PS) is a rare but accepted risk factor for venous thromboembolism. There is accumulating evidence that inherited PS deficiency may be associated with a variety of adverse obstetric events. Acquired PS deficiency may be caused by a variety of clinical states including normal pregnancy. We conducted a retrospective audit of the results of screening for PS deficiency through our reference laboratory. The majority of patients in this audit with significantly reduced (<50%) free functional PS levels had a major confounding factor likely to cause acquired PS deficiency, most frequently pregnancy. Recommendations for PS testing for the diagnosis of hereditary PS deficiency include deferring testing until at least 40 days post-partum. It appears that these recommendations are not being adhered to leading to difficulty in the interpretation of results.

Emerging technologies and quality assurance in hemostasis: a review of findings from the Royal College of Pathologists of Australasia Quality Assurance Program

Regular multilaboratory surveys of laboratories by the Royal College of Pathologists of Australasia Quality Assurance Program (QAP) have been conducted to assess proficiency in tests of hemostasis for the last 40 years. This article focuses primarily on specialized assays of hemostasis, for which surveys have been conducted for some 10 years. For von Willebrand disease (vWD) evaluations, a total of 47 plasma samples have been dispatched to survey participants, including representative samples from normal individuals plus all of the major vWD subtypes (i.e., types 1, 2A, 2B, 2M, 2N, and 3). These surveys have focused partly on the issue of diagnostic interpretive error rates associated with different assays and test panels. In this context, considerable improvement is seen when laboratories incorporate the vWF:collagen-binding assay into the test panel. Thrombophilia-associated tests assessed by the program and discussed in this review include activated protein c resistance, lupus anticoagulant, and deficiencies of protein C, protein S, and antithrombin. Other tests briefly reviewed here include factor assays and inhibitors, D-dimer, and heparin/anti-Xa assays. Anticardiolipin antibody and anti-beta(2)-glycoprotein I antibody (aB(2)GPI) testing, assessed by the Immunology QAP, is also reviewed briefly, as are genetic tests associated with thrombophilic markers such as factor V Leiden and the prothrombin gene.

Intracardiac thrombus and pulmonary embolism with cavitation and pneumomediastinum in a patient with protein S deficiency

We present a case of intracardiac thrombus with pulmonary embolism and pulmonary infarction in a patient with protein S deficiency. Secondary infection of the pulmonary infarction resulted in pneumomediastinum. Thrombus in an unusual location in a young patient without known predisposing conditions is a characteristic feature of a hereditary thrombophilic disorder. Cavitation within a lesion adjacent to the mediastinal pleura can result in pneumomediastinum.

Utility of Thrombin-Generation Assay in the Screening of Factor V G1691A (Leiden) and Prothrombin G20210A Mutations and Protein S Deficiency

Background: The thrombin-generation assay has a variety of clinical uses, including diagnosis of thromboembolism-related disease, and particular profiles are associated with thrombophilic risk factors. The aim of this study was to evaluate the use of this assay in screening and identifying patients who require specific thrombophilic testing.

Methods: We used a 2-step approach to perform specific thrombophilic testing and thrombin-generation assays on 169 consecutive patients. The first step was to identify particular profiles of thrombin generation corresponding to each type of thrombophilic risk factor and to determine the pertinent variables related to thrombin generation. We then performed ROC curve analysis for each predefined variable to determine the relevant cutoffs for identification of patients in need of further testing (negative predictive value, 100%).

Results: Suggestive profiles were seen in factor V Leiden (n = 49) and prothrombin (n = 12) mutations and in protein S deficiency (n = 12). ROC curves showed that factor V Leiden may be excluded when the difference between lag times obtained in the absence and presence of activated protein C (APC) is &gt;1.5 min and that prothrombin G20210A may also be excluded when the peak thrombin concentration is ≤426 nmol/L. In addition, protein S deficiency may be excluded when the percentage of APC-induced endogenous thrombin potential inhibition is &gt;63%.

Conclusion: The thrombin-generation assay represents a promising tool for screening thrombophilic risk factors, particularly in patients who are carriers of factor V Leiden or prothrombin G20210A mutations and patients with protein S deficiency.

Hemiconvulsion, hemiplegia, epilepsy syndrome and inherited protein S deficiency

A nine-year-old Nepalese girl developed hemiconvulsion, hemiplegia, epilepsy syndrome (HHE syndrome) after an episode of right-sided focal status epilepticus following acute gastroenteritis. She had left middle cerebral artery (MCA) territory infracts due to inherited protein S deficiency.

[Spontaneous skin necrosis from acquired protein S deficiency in a renal transplant recipient]

INTRODUCTION

Spontaneous skin necrosis revealed acquired protein S deficiency due to isotype G autoantibodies.

CASE

This 31-year-old male renal transplant recipient, receiving immunosuppressive treatment, was hospitalized for necrotic purpural lesions. We were not able to detect any triggering factor. Sustained anticoagulant therapy remained essential to prevent new skin lesions and perhaps more thrombotic events.

COMMENTS

This condition is rare in adulthood, but is well described in children's purpura fulminans, especially the post-varicella form. Its mechanism remains unclear.

Alexia without agraphia following cerebral venous thrombosis associated with protein C and protein S deficiency

A 26-year-old right handed female was admitted to hospital with right homonymous hemianopia associated with alexia without agraphia. Her cranial magnetic resonance imaging and magnetic resonance angiography revealed a left occipital venous infarction due to thrombosis of the left transverse, sigmoid sinuses and the left internal jugulary vein. The underlying conditions were protein C and protein S deficiency associated with the use of oral contraceptives. To our knowledge, alexia without agraphia has never been described due to a venous infarction associated with hereditary thrombophilia in the literature.

[Abnormalities of haemostasis in myocardial infarction with normal coronary artery]

Myocardial infarction with normal coronary artery is ussually inaugural, with electric and clinical characteristics similar to those with atheroma. The role of constitutional or acquired abnormalities of haemostasis has been more incriminated in the pathogenesis of myocardial infarction with normal coronary. The aim of our study was to research abnormalities of haemostasis in patients with myocardial infarction and angiographically absolutely normal coronary arteries.

PATIENTS AND METHODS

Thirty nine patients with myocardial infarction and normal coronary arteries where included in our study. They were 33 males and 6 females aged between 22 and 75 years (44 + 13 years), in whom the deficiency in protein C and S. antithrombin, activated protein C resistance and antiphospholipid antibodies were assessed.

RESULTS

Concurrent abnormalities of haemostasis were found in 10 patients: Antiphospholipid antibodies, found in 5 patients constitute the most frequent abnormality. The other abnormalities were deficiency in protein C in two cases, deficiency in protein S 2 cases, deficiency in antithrombin in 2 ceses and activated protein C resistance in 3 cases .

CONCLUSION

In our study. in face of the high prevalence of these abnormalities, it seems reasonable to research them, especially in young patients with myocardial infarction with normal coronary artery. This should have an impact on the management of these patients.

Prevalence of Prothrombotic Abnormalities in Patients with Acute Mesenteric Ischemia

Acute mesenteric ischemia (AMI) is a rare condition that may be associated with a variety of congenital prothrombotic disorders (PDs). The purpose of this study was to assess the prevalence of these disorders in 28 AMI patients compared with 103 healthy individuals from the northeastern region of Turkey. They were screened for protein C, antithrombin III, and protein S deficiencies; and gene analysis was performed using the polymerase chain reaction. A PD was revealed in 16 (57%) patients and 33 (32%) controls (p = 0.020). Factor V Leiden (FVL), prothrombin G20210A mutation, and TT677 homozygous mutation of methylenetetrahydrofolate reductase was detected in 10 (36%) patients versus 16 (15%) controls (p = 0.035), 3 (11%) patients versus 10 (9%) controls (p = 1.00), and 1 (3%) patient versus no controls, respectively. Consistent with caucasian ethnic groups, there was high prevalence of PDs, especially FVL; and these abnormalities might be a significant predisposing factor in the pathogenesis of AMI.

Purpura fulminans as a sequel to erythema nodosum in a child with homozygous Leiden mutation and acquired protein S deficiency

A 6-y-old boy presented with generalized, bruise-like swelling of both legs. Three weeks later, he developed purpura fulminans in one of the affected feet. Histology of the leg swelling was in accordance with erythema nodosum. The boy proved to be homozygous for the Factor V Leiden mutation and to have acquired protein S deficiency. He recovered, with partial loss of two toes.

CONCLUSION

In contrast to what is often stated, erythema nodosum is not always a benign condition. On the basis of this report, we suggest that if extensive erythema nodosum develops in an individual without any known thrombophilic disorder, investigations with respect to the latter should be performed.

[Atypical venous thrombosis and protein S deficiency: report of a case]

A 29 year old man is admitted for hypovemic shock and abdominal pain. This critical condition was due to a diffuse mesenteric venous thrombosis and intestinal infarction. Five meters of small bowel are resected. Few days later a superficial brachial venous thromboembolism grows to superior cava venous and bilateral pulmonary embolism. A plasmatic protein S level was 17%. This deficiency is considered to be the support of these atypical extended and repetitive venous thromboembolism. With an optimal nutrition and long oral anticoagulation this patient is alive 17 months after his admission.

Venenastverschluss und Abduzensparese bei Protein-S-Mangel

BACKGROUND

Protein S deficiency, which exists in 0.7% of the population, is a risk factor for retinal vein branch occlusions and is inherited in an autosomal dominant manner.

METHODS

A genealogical study was carried out on three generations of one family who exhibited different venous occlusions and subsequent complications.

RESULTS

Four members of the family, spanning three generations, suffered from complications of venous thrombosis. In the first generation a great uncle died of complications from a deep leg venous thrombosis. In the second generation, the mother underwent a venous branch thrombosis at the age of 41 with a protein S activity of 18%. Subsequently, a palsy of the N. abducens developed with multiple cerebral lesions (presumably post-thrombotic) in the MRI. Fluorescein angiography showed a typical picture of a venous branch occlusion which had been treated by laser. In the third generation, the 16-year-old daughter developed iliac venous thrombosis and a pulmonary embolism with a protein S activity of 0%. The fluorescein angiography showed distinctively engorged veins. A 28-year-old daughter, with a protein S activity of 16%, remained asymptomatic, although fluorescein angiography demonstrated engorged veins. Protein C activity and APC resistance of all family members were normal. The chromosomal analysis of the family members revealed no morphological aberrations.

CONCLUSION

Protein S deficiency increases the risk of congenital thrombosis in young and middle-aged heterozygous individuals.

Hemorrhagic stroke in a child with protein S and factor VII deficiencies

A 12-year-old previously healthy male, with a family history of protein S deficiency, presented with confusion, aphasia, and right upper extremity weakness after a 10-day febrile illness. Imaging studies revealed sinovenous thrombosis and left parietal hemorrhagic stroke. On further investigation he was found to have both protein S and factor VII deficiencies.

Preliminary Study of Simultaneous Multi-Anticoagulant Deficiency Diagnosis by Fiber Optic Multi-Analyte Biosensor

Protein C (PC), protein S (PS), antithrombin III, and plasminogen are four important anticoagulants in blood plasma. Deficiency of any of these biomolecules may lead to thrombo-embolic complications including lung embolism, heart attack, and stroke. A multi-factor sensing system is beneficial for identifying the cause of abnormal blood clotting more effectively, rapidly, and cost-effectively. As an initial effort toward simultaneous multi-anticoagulant detection, a PC and PS dual-sensing system has been under development in our research group. A fiberoptic PC biosensor utilizing fluorophore-mediated sandwich immunoassay was already developed for rapid (-5 minutes) PC deficiency diagnosis. After a single PS sensor was developed for the PS deficiency diagnosis, the two sensors were connected in series to form a dual-sensing system. The cross-reactivity between the analytes and the sensors was found to be minimal. For easier sensing operation, a mixture of fluorophore-linked anti-PC and anti-PS was applied. The results showed that the mixture can be used with a slight signal reduction. When PC and PS was mixed in a sample, the signal intensity was decreased by approximately 5% for both sensors. A study is currently being performed to overcome the signal reduction by increasing the flow velocity and incubation time.

[Homocystein and cardiovascular risk: is dosage useful?]

Hyperhomocysteinemia represents an independent risk factor for atherothrombotic disease. Physiopathological mechanisms of accelerated progression of atherosclerosis in presence of hyperhomocysteinemia are complex. Herein we report a clinical case which emphasis the importance of screening elevated homocystein in the absence of conventional risk factors in patients who suffer from premature atherosclerosis.

Normal Functional Protein S Activity Does Not Exclude Protein S Deficiency

Protein S (PS) deficiency appears to increase the risk of venous thrombosis. PS deficiency is classified into three phenotypes using antigenic levels and functional activity. By definition, all three phenotypes of PS deficiency should result in low activated protein C cofactor activity. We compared the results of functional PS activity testing to free antigenic PS testing in order to determine if a normal functional PS activity assay result could eliminate the need for free antigenic PS testing. The sensitivity of the functional assay is 45.5% (95% confidence interval, CI, 36-55%), specificity 95.3% (95% CI 93-97%), negative predictive value 88.6% (95% CI 86-91%) with a positive predictive value of 68.5% (95% CI 57-79%). In conclusion, a normal functional PS activity result does not exclude free antigenic PS deficiency. Functional PS activity testing should not be used as a screening test to eliminate free antigenic PS testing for the laboratory diagnosis of PS deficiency.