Vitamin K-dependent Coagulation Factors Research Articles

Antithrombotic Activity of the Novel Oral Anticoagulant, Tecarfarin [Sodium 3-[4-((1,1,1,3,3,3-hexafluoro-2-methylpropan-2-yloxy) carbonyl) benzyl]-2-oxo-2H-chromen-4-olate] in Animal Models

The antithrombotic activity of tecarfarin, a novel orally active vitamin K epoxide reductase inhibitor, was assessed in canine and rabbit thrombosis models. In dogs, once-daily oral doses of 0.5 mg/kg tecarfarin selectively reduced the levels of the vitamin K-dependent coagulation factors (factors II, VII, IX, and X) and prolonged the prothrombin time (PT). A 4 to 7 day course of oral tecarfarin (0.05 - 0.5 mg/kg) prolonged the PT by 3 to 5-fold and reduced thrombus formation in arterial and venous segments subjected to a combination of electrical injury and flow-limiting constriction. To compare the effects of tecarfarin with those of warfarin, rabbits were given once-daily oral doses of 1 mg/kg tecarfarin, 1.5 mg/kg warfarin, or saline for 2 days. After verifying increases in the PT with tecarfarin and warfarin, blood loss from standardized ear incisions was measured to assess hemorrhagic potential. Then, after intravenous injection of 125I-labeled rabbit fibrinogen, thrombosis was induced in an isolated jugular vein segment by a combination of balloon catheter-induced endothelial denudation and venous occlusion. Compared with the saline control, both tecarfarin and warfarin prolonged the PT, increased blood loss from the ear incisions, and attenuated thrombus formation. Thus, like warfarin, tecarfarin attenuates venous and arterial thrombus formation in animal models by reducing the levels of the vitamin K-dependent coagulation factors.

Relationship between acquired deficiency of vitamin K-dependent clotting factors and hemorrhage

This study examined the changes of activities of vitamin K-dependent clotting factors (VKDCF) under various pathological conditions and explored the relationship between acquired deficiency of VKDCFs and hemorrhage. Clinical data of 35 patients who were diagnosed as having acquired deficiency of VKDCF were retrospectively analyzed. Coagulation factors involved in the intrinsic and extrinsic pathways were detected in these patients and 41 control subjects. The results showed that the average activities of VKDCFs were decreased in the patients in comparison to the control subjects and significantly increased after treatment of these patients with vitamin K and blood products. Multivariate regression analysis indicated that decreased activity of VKDCF was not an independent risk factor for bleeding disorders owing to deficiency or metabolic disturbance of vitamin K. It was concluded that acquired deficiency of VKDCF occurs under a variety of pathologic conditions and is closely associated with hemorrhagic events. Administration of vitamin K and transfusion of blood products containing high concentrations of VKDCFs helps alleviate the hemorrhagic diseases.

Purification of coagulation factor VIII using chromatographic methods. Direct chromatography of plasma in anion exchange resins

Coagulation factor VIII (FVIII) concentrates are used in the treatment of patients with Hemophilia A. Human FVIII was purified directly from plasma using anion exchange chromatography followed by gel filtration. Three Q-Sepharose resins were tested, resulting in 40% recovery of FVIII activity using Q-Sepharose XL resin, about 80% using Q-Sepharose Fast Flow and 70% using the Q-Sepharose Big Beads. The vitamin K-dependent coagulation factors co-eluted with FVIII from the anion exchange columns. In the second step of purification, when Sepharose 6FF was used, 70% of FVIII activity was recovered free from vitamin K-dependent factors.

Comprehensive Pediatric Care of Rare Bleeding Disorders

Although less common than hemophilia or von Willebrand disease, inherited rare bleeding disorders, comprising afibrinogenemia and deficiencies in factors II, V, VII, X, XI, XIII or V plus VIII combined, or in vitamin K-dependent coagulation factors, may lead to severe bleeding episodes such as recurrent hemarthroses and neonatal intracranial or gastrointestinal hemorrhage. Consanguinity significantly increases the risk of the occurrence of all rare bleeding disorders that are associated with an autosomal recessive pattern of inheritance. Each of the disorders is characterized by a wide interindividual variation in clinical phenotype and a large mutational spectrum with no clear correlation between the phenotype and genotype. Replacement therapy relies on specific molecules or concentrates (afibrinogenemia, factor VII, XI and XIII deficiencies), on a mixture of different concentrates that are otherwise known as a prothrombin complex, which contains factors II, VII, IX and X, or on fresh frozen plasma. International consensus guidelines for treatment modalities are progressing; however, guidelines for prophylaxis, especially in pediatric patients, are lacking.

High-level expression of functional recombinant human coagulation factor VII in insect cells

Recombinant coagulation factor VII (FVII) is used as a potential therapeutic intervention in hemophilia patients who produce antibodies against the coagulation factors. Mammalian cell lines provide low levels of expression, however, the Spodoptera frugiperda Sf9 cell line and baculovirus expression system are powerful systems for high-level expression of recombinant proteins, but due to the lack of endogenous vitamin K-dependent carboxylase, expression of functional FVII using this system is impossible. In the present study, we report a simple but versatile method to overcome the defect for high-level expression of the functional recombinant coagulation FVII in Sf9 cells. This method involves simultaneous expression of both human gamma-carboxylase (hGC) and human FVII genes in the host. It may be possible to express other vitamin K-dependent coagulation factors using this method in the future.

Genotype polymorphisms of GGCX, NQO1, and VKORC1 genes associated with risk susceptibility in patients with large-artery atherosclerotic stroke

Backgroundγ-Glutamyl carboxylation, a reaction essential for the biosynthesis of vitamin K-dependent coagulation factors, requires the participation of the γ-glutamyl carboxylase (GGCX), vitamin K epoxide reductase (VKORC1), and NAD(P)H:quinone oxidoreductase (NQO1). We evaluated the role of these genotype polymorphisms in patients with large-artery atherosclerotic stroke. MethodsIn this hospital-based case–control study, 117 patients who were categorized as having large-artery atherosclerotic stroke and 115 age- and gender-matched controls were recruited. Genotyping determination for the GGCX1 (Gln325Arg), NQO1 (Pro187Ser), and VKORC1 (rs9923231) polymorphisms was performed. The associations of genotype with ischemic stroke (IS) risk were examined. ResultsA higher genotypic frequency of NQO1 C609T was found in the controls than in the patients, manifesting a 0.47-fold risk reduction in IS (95% CI=0.25–0.87). A tendency toward a reduced IS risk was statistically significant in those subjects who carried a greater number of the NQO1, GGCX, and VKORC1 polymorphisms (aOR=0.58, Ptrend=0.005). The synergistic effect of multiple genes on risk reduction was more significant in a subset of patients who were not alcoholics and who were non-smokers (P<0.05). ConclusionsCompartmentation of coagulation factor metabolism may account for the preferential role of NQO1, GGCX, and VKORC1 polymorphisms to lower the risk for large-artery atherosclerotic stroke.

Dabigatran, A Direct Thrombin Inhibitor, In Atrial Fibrillation: Is It Already Time For A Change In Oral Anticoagulation Therapy?

Atrial fibrillation (AF) is a common arrhythmia, and its prevalence increases with aging and the severity of heart disease. AF affects more than 2 million peo-ple in the US, and more than 4 million in Europe. It is expected that the age adjusted prevalence in US will excede 10 million people by the year 2050 [1-5]. In the last decade, we were able to see the light shed by several trials that dealt with AF mecha-nisms and the appropriate management of AF pa-tients. Clinical studies have focused mainly on the electrophysiological properties of the substrate in the atrial muscle during sinus rhythm and on the atrial electrical responses elicited by premature stimulation method [6-9]. However, many funda-mental aspects of this arrhythmia have been poorly understood until quite recently, and there are sev-eral features on the mechanisms of AF that makes it difficult to manage it properly. Increasing aware-ness of AF as a disease with possible fatal compli-cations rather than as an acceptable alternative to sinus rhythm has led to search for clear arguments to support a certain strategy as a golden standard. There is no atrial contraction during AF, a situation that renders the pooled blood inside the atrium susceptible to develop thrombus formation par-ticularly in the left atrium. AF increases the overall risk of stroke five-fold, and is associated with par-ticularly severe strokes [10-12]. About 76% of AF patients have a moderate to high risk of embolic complications, and they have also a significant risk factor for stroke recurrence [13-15]. It looks very clear that all the difficulties we have to face in find-ing proper answer to its therapeutic management. Vitamin K antagonist drugs, such as warfarin and acenocumarol, reduce the risk of AF-related stroke by about 70% [4, 16]. They are the only oral antico-agulants currently recommended for the preven-tion of stroke in patients with a moderate to high risk of stroke [15] These pharmacological agents produce their anticoagulant effect by preventing the g-carboxylation of the vitamin K-dependent coagulation factors prothrombin and Factors VII, IX, and X [17]. Despite the good clinical results obtained with these oral anticoagulants that are far from being ideal [Table 1], there are some in-convenient factors which make their conventional use difficult to implement and follow. There is a consistent suboptimal utilization of oral anticoag-ulation therapy. Warfarin is prescribed to only two thirds of appropriate candidates despite guide-lines recommendations [18]. The narrow therapeu-tic window in the anticoagulation process makes it neccessary to monitor closely the prothrombin time. Insufficient anticoagulation may result in embolic complications, while over-anticoagula-tion increases the risk of bleeding [19]. There are also other disadvantages related to the unpredict-able pharmacokinetics and pharmacodynamics of these oral anticoagulants, which are affected by genetic factors, drug to drug interactions, and con-sumption of foods containing vitamin K. There-fore, it is paramount that a regular coagulation monitoring and dose adjustment is necessary to ensure adequate anticoagulation. This fact leads to high rates of discontinuation of therapy, and many patients remaining on therapy have also in-adequate anticoagulation. Another important is-sue is the concern about real-world effectiveness which was found to be around 35% [18]. It is clear to see that there is a great need of new oral antico-agulants for stroke prevention in patients with AF.Connolly et al [20] reported recently in the New England Journal of Medicine, the clinical findings

Amphipathic peptides can act as an anticoagulant by competing with phospholipid membranes for blood coagulation factors

An ideal amphipathic peptide (IAP), composed of simply lysine and leucine residues in a 1:2 ratio (K 7L 15), specifically prolongs in vitro coagulation assays that use phospholipids, such as the activated partial thromboplastin time (APTT). The main hypothesis of the present work is that IAP’s anticoagulant effect occurs by competing with phospholipid membranes in in vitro coagulation reactions. We verified this hypothesis by employing different phospholipid-dependent coagulation assays, such as the APTT, the dilute prothrombin time (dPT) and the dilute Russell viper venom time (dRVVT) with both low and high amounts of phospholipids. We show that coagulation times are prolonged by IAP in a concentration-dependent manner, and that this prolongation is abrogated by adding excess phospholipid, demonstrating a phospholipid dependence for this inhibition. Using an ELISA-based binding assay, we show IAP inhibits the binding of one of the vitamin K-dependent coagulation factors, factor X, to phospholipid membranes. This is further confirmed with fluorescence spectroscopy, where the interaction of IAP and factor X is inhibited by phospholipid. In summary, this work demonstrates that IAP can act as an anticoagulant by impairing the interaction of coagulation factors with phospholipid membranes and provides a paradigm for the development of novel anticoagulants.

Gla-Rich Protein Is a Novel Vitamin K-Dependent Protein Present in Serum That Accumulates at Sites of Pathological Calcifications

Mineralization of soft tissues is an abnormal process that occurs in any body tissue and can greatly increase morbidity and mortality. Vitamin K-dependent (VKD) proteins play a crucial role in these processes; matrix Gla protein is considered one of the most relevant physiological inhibitors of soft tissue calcification know to date. Several studies have suggested that other, still unknown, VKD proteins might also be involved in soft tissue calcification pathologies. We have recently identified in sturgeon a new VKD protein, Gla-rich protein (GRP), which contains the highest ratio between number of Gla residues and size of the mature protein so far identified. Although mainly expressed in cartilaginous tissues of sturgeon, in rat GRP is present in both cartilage and bone. We now show that GRP is a circulating protein that is also expressed and accumulated in soft tissues of rats and humans, including the skin and vascular system in which, when affected by pathological calcifications, GRP accumulates at high levels at sites of mineral deposition, indicating an association with calcification processes. The high number of Gla residues and consequent mineral binding affinity properties strongly suggest that GRP may directly influence mineral formation, thereby playing a role in processes involving connective tissue mineralization.

Comparative Studies On Heparin Contaminant Interactions with Normals, Liver Disease, Heparin Treated and Oral Anticoagulant Treated Patients Plasma.

Abstract 2093Poster Board II-70Heparin, a conventionally used anticoagulant, manufactured during the period of November 2007 to April 2008 was recalled by the United States Food and Drug Administration due to severe adverse complications and deaths. Further investigations revealed that heparin was contaminated with oversulfated chondroitin sulfate (OSCS). Most of the coagulation factors are produced in the liver and acute or chronic hepatocellular failure may cause significant decrease in the vitamin K-dependent coagulation factors such as Factors II, VII, IX and X and also protein C and protein S. It is important to study the effects of OSCS in patients treated with coumadin, heparin and in patients with liver disease. It was hypothesized that OSCS causes synergistic interactions with coumadin, heparin and may cause adverse effects when administered in patients with liver disease. In order to validate this hypothesis OSCS from different sources such as Bovine OSCS, Shark OSCS and Porcine OSCS were supplemented in plasma samples obtained from coumadinized, heparinized and liver diseased patients. Each of these agents was supplemented in these sets of plasma samples at a final concentration of 2.5ug/ml. Saline was also supplemented in these plasma samples which served as control. These different OSCS were also supplemented in the plasma samples obtained from normal healthy volunteers. Global clotting assays such as prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) 5Units/ml were performed. Significant prolongation of the PT, APTT and TT 5U/ml when compared to saline control, was observed in icteric plasma samples and a slight prolongation in coumadinized and heparinized plasma samples was observed (as depicted in the following table).% Increase in the clotting profile in normal, coumadinized, heparinized and icteric plasma samplesGroupSalineBOSCSShOSCSPOSCSPTAPTTTTPTAPTTTTPTAPTTTTPTAPTTTTNormal10.032.815.417.140.267.414.443.880.017.639.464.5High PT13.134.526.521.798.4305.223.5217.8337.618.0252.1266.5High APTT11.356.139.026.4215.2340.132.3200.7315.318.7263.5350.1Icteric11.333.025.519.772.8247.330.3349.3623.423.8430.8407.8These results suggest that OSCS from various sources produced marked augmentation of the anticoagulant responses in plasma samples collected from patients treated with oral anticoagulants and heparin. Most notably the heparin components produced a relatively stronger anticoagulant effect in the plasma samples in liver disease patients. It is also interesting to note that the individual contaminants in shark and porcine OSCS produced its own assay dependent effects which were most pronounced in the liver disease patients. These results strongly suggest that the heparin contaminant may augment the anticoagulant and bleeding effects in patients with anticoagulant and hypocoagulable states. Disclosures:No relevant conflicts of interest to declare.

Compound Heterozygosity of a W493C Substitution and R704/Premature Stop Codon within the γ-Glutamyl Carboxylase in Combined Vitamin K-Dependent Coagulation Factor Deficiency in a French Family.

Abstract 1302Poster Board I-324Combined vitamin K-dependent (VKD) coagulation factor deficiency is an autosomal recessive bleeding disorder associated with defects in either the γ-carboxylase (GGCX) which carboxylates VKD proteins to render them active or the vitamin K epoxide reductase (VKORC1) which supplies the reduced vitamin K cofactor required for carboxylation. Such deficiencies are rare, and due to mutations within either gene. Of note some mutations within the GGCX gene have recently been found associated with the pseudoxanthoma elasticum (PXE) syndrome, suggesting a role for GGCX in skin development. We report a new case of combined VKD coagulation factor deficiency resulting from two mutations in the GGCX gene, and the first identified in a French child, who exhibited impaired function in hemostatic VKD factors. The propositus exhibited bleeding at sites of venipuncture at birth, and at the age of 3 months was admitted in emergency for spontaneous multiple hematomas of the chest and thighs; recently, at the age of 1 year, he exhibited a hematoma of the wrist following a casual fall. Coagulation and VKD factors were low [PT (Control/patient): 12.8/>100 sec; II : 3 % ; VII :2% ; X :3%] while the non-VKD factor V was normal (105%). Vitamin K infusion corrected the bleeding tendency as well as coagulation paramenters [PT (Control/patient): 12.8/14.8 sec; II :72% ; VII+X : 62%; factor V remained normal at 102%]. Family analysis revealed that both parents and one brother were unaffected, both clinically and biologically, but that a brother had died of an unexplained abdominal hemorrhage, in the neonatal period. Taken together the clinical family history is consistent with a recessive trait. No sign of PXE was found in the family. DNA sequence analysis of the propositus did not identify any mutations in the VKORC1 gene but revealed two new heterozygous mutations in the carboxylase gene: a G10233T transversion in exon 11 (G1565U in mRNA) that caused an W493C substitution and a C12078T transition in the last exon (15) (C2196U in mRNA) that caused a premature R704stop, presumably deleting the last 55 C-terminal amino acids. W493 is a highly conserved amino acid and its homozygous mutation (for S493) has recently been reported in a case of VKD coagulation factor deficiency associated with PXE. R704 mutation has never been reported previously. Family analysis showed that W493C was transmitted by the father, R704stop by the mother, that the deceased brother carried both mutations, while the unaffected brother carried neither. Mutational analysis was carried out by site-directed mutagenesis of the GGCX cDNA subsequently subcloned into the BacPak8 baculovirus-based vector, and GGCX was expressed in the virally-infected SF21 insect cell line. Protein expression level of the enzyme was assessed by western blotting, and enzymatic activity was evaluated by measuring the incorporation of [14]C-CO2 within the Boc-Glu-Glu-Leu-OMe peptide. No difference in expression level was detected for either mutant protein compared to the wild type protein. However, while no difference in molecular weight was seen between the W493C mutant and wild type on wertern blotting, the R704stop mutation generated a shorter form of carboxylase than wild type, consistent with the predicted shorter reading frame. W493C mutant exhibited a much lower activity than wild type, suggesting a functional role for W493. The activity of the R704stop mutant is currently being assessed, as well as the activity of the coexpressed mutants. Since PXE has been correlated with a W493S mutation, a role for the W493C mutation in future development of PXE in this young patient will be assessed during follow-up. DisclosuresNo relevant conflicts of interest to declare.

Prothrombin Complex Concentrate (Beriplex® P/N)

Beriplex P/N, a prothrombin complex concentrate derived from pooled human plasma, contains the vitamin K-dependent coagulation factors II, VII, IX and X, and the vitamin K-dependent coagulation inhibition proteins C and S. Intravenous Beriplex P/N provided rapid and sustained normalization of elevated international normalized ratios and controlled bleeding in adult patients participating in several prospective, noncomparative clinical studies (n = 8-43), with these data supported by clinical experience during its use over more than a decade. Based on extensive clinical experience, Beriplex P/N is also effective in the treatment of congenital deficiency of any of the vitamin K-dependent coagulation factors when purified specific coagulation factor products are not available. Over a decade of clinical experience and more limited data from clinical studies have shown that intravenous infusions of Beriplex P/N were generally well tolerated in adult patients with acquired or congenital deficiencies of the vitamin K-dependent coagulation factors. To date, there have been no proven cases of viral transmission reported in any published studies.

Direct thrombin inhibitors in atrial fibrillation reloaded

Inhibition of plasmatic coagulation is the key therapeutic principle for thromboprophylaxis and stroke prevention in atrial fibrillation. The coagulation cascade is initiated by contact of tissue factor (TF) with circulating factor (F) VIIa, resulting in the formation of the TF–VIIa complex. The latter catalyses the conversion of FIX to IXa and FX to Xa. Together with FVa, phospholipids, and calcium, FXa forms the ‘tenase’ or ‘prothrombinase’ complex, which catalyses the conversion of prothrombin (FII) to thrombin (FIIa), eventually resulting in fibrin formation and generation of a thrombus.1 Thrombin furthermore activates FV, FVIII, and FXI by means of an auto-feedback loop, leading to the conversion of large amounts of FX to FXa and thereby to a sustained activation of coagulation ( Figure 1 ). Figure 1 Coagulation cascade and novel anticoagulants. (modified from Steffel and Luscher3). For decades, vitamin K antagonists (VKAs), which prevent γ-carboxylation of vitamin-K dependent coagulation factors II, VII, IX, and X, have been the mainstay of therapy for stroke prevention in atrial fibrillation.2 However, several downsides mainly related to their narrow therapeutic window are associated with long-term anticoagulation, necessitating life-long monitoring of coagulation intensity (initially 2–3 times weekly, later at least once monthly). Indeed, subtherapeutic as well as supratherapeutic anticoagulation with VKAs are associated with a substantial risk of recurrent events and bleeding (especially intracranial and gastrointestinal), respectively. Not surprisingly, novel anticoagulants have been and are being developed for stroke prevention in atrial fibrillation in order to replace VKAs.3 In contrast to the latter, these new substances selectively inhibit central proteins of the coagulation cascade ( Figure 1 ). Selective inhibitors of FXa and thrombin have turned out to be the most promising therapeutic principles in this regard. … *Corresponding author. Tel: +41 44 255 1111, Fax: +41 44 255 8701, Email: steffel{at}access.uzh.ch

Implications of Pharmacogenetics for Oral Anticoagulants Metabolism

Oral anticoagulants, the main drugs used for the prevention and treatment of thromboembolic diseases, are a leading cause of fatal haemorrhagic complications due to the variable reactions that different patients can have when taking the drugs. The reaction to coumarins is affected by both diet such as the patient daily intake of vitamin K, and also by genetically determined levels of critical proteins. Clinically available, warfarin consists of a racemic mixture of two active optical isomers, (R)- and (S)- isoforms, and their pharmacokinetic and pharmaco-dynamic properties differ considerably, because the (S)-enantiomer is three times more potent than the (R)-enantiomer. Metabolism of warfarin occurs through the action of three different cytochrome P-450 enzymes. S-warfarin, predominantly responsible for the anticoagulation effect, is metabolized mostly by the CYP2C9 enzyme. A number of polymorphisms in CYP2C9 gene have been identified but the most important are CYP2C9*2 and CYP2C9*3. The second enzyme that is involved in coumarins metabolism is the vitamin K epoxide reductase (VKORC). This enzyme is the target of coumarins and converts oxidized vitamin K to the reduced active form that is required for the post-translational (gamma) carboxylation of the vitamin K-dependent coagulation factors. VKORC activity levels are affected by several polymorphisms that can be divided into high or low level haplotypes. There is a considerable controversy about the clinical use of genotyping before starting the anticoagulant therapy so, further randomized, prospective and large trials are required to recommend the use of pharmacogenetic testing.

Vitamin K–Dependent Coagulation Factors Deficiency

All vitamin K-dependent coagulation factors require normal function of gamma-glutamyl carboxylase and vitamin K epoxide reductase enzyme complex (VKORC1). Heritable dysfunction of gamma-glutamyl carboxylase or of the VKORC1 complex results in the secretion of poorly carboxylated vitamin K-dependent proteins that play a role in coagulation. The following review will summarize the clinical manifestations of vitamin K-dependent coagulation factors deficiency I and II and will provide a detailed explanation about the gene and protein structure, the function of the protein, and an analysis of the previously reported mutations. Laboratory assays used for diagnosis will be discussed, and treatment for various clinical settings will be recommended.

Warfarin in vulnerable older adults with atrial fibrillation

Current indications for anticoagulant therapy in the primary or secondary prevention of thromboembolism span a vast array of clinical syndromes in cardiovascular medicine, from nonvalvular atrial fibrillation (AF) to prosthetic mechanical valves, and the prophylaxis of arterial or venous thrombosis [1, 2]. The complexities of vitamin K antagonist (VKA) administration among patients with AF is heightened substantially in older adults who, in addition to comborbid illness, pose a risk for both thrombotic and hemorrhagic events-either of which can be life-altering or life-threatening. VKAs, of which warfarin is the most widely used and investigated coumarin derivative, exerts its anticoagulant effects though modulating c-carboxylation of glutamic acid (GLA) residues of the vitamin K-dependent coagulation factors II, VII, IX, and X, resulting in the production of coagulation factors with reduced coagulant capacity [3]. The estimated disease prevalence of AF is 9% among octogenarians, and given global aging, the total AF burden of disease is expected to double by 2050 [4]. Complexities in decision making around the use of VKAs are magnified among the population of vulnerable older adults with functional decline, nutritional deficiencies, polypharmacy, frailty, falls, and cognitive dysfunction—clinical and health-related characteristics that collectively define the older adult with prototypical geriatric syndromes [5–7]. Vulnerability has been previously operationalized and defined as ‘‘community-dwelling seniors who have four times the risk for functional decline or death over the next 2 years compared with those not identified as vulnerable’’ [8]. This phenotype has previously been captured, employing either self or proxy reporting on aspects of functional status, and collectively represent conditions frequently encountered in the practice of geriatrics [9]. Accordingly, the direct application of evidence from existing guidelines and clinical studies on the benefits of anticoagulant therapy for conditions, like AF, that are known to increase the risk of thrombosis-related clinical events must be balanced carefully by considering both the number needed to harm (NNH) and the ‘‘values and preferences’’ of care for an individual patient. The absolute benefit of VKA over antiplatelet therapy among the very elderly with geriatric syndromes continues to be an area of uncertainty, despite being encountered frequently in clinical practice. Building upon the overarching theme of hemostasis and thrombosis in older adults [10], herein we consider the landscape of VKA treatment among vulnerable older adults—offering a paradigm of thrombotic risk, bleeding propensity, and individualized decision making to include cessation of treatment when the likelihood of harm outweighs the potential benefit.

Novel splice site mutations in the gamma glutamyl carboxylase gene in a child with congenital combined deficiency of the vitamin K‐dependent coagulation factors (VKCFD)

Congenital combined deficiency of the vitamin K-dependent coagulation factors is a rare bleeding disorder caused by either a defect in the gamma-glutamyl carboxylase or the vitamin K epoxide reductase enzyme complex. The diagnosis should be considered when vitamin-K dependent factor activities are decreased and liver dysfunction, vitamin K deficiency, and factitious coumarin ingestion have been excluded. We report a case of VKCFD in a child resulting from compound heterozygosity for two novel splice site mutations of the gamma-glutamyl carboxylase gene. Oral vitamin K supplementation resulted in partial resolution of proteins and complete resolution of bleeding.

Personalizing Health Care—Is This the Right Time for Warfarin?

Personalizing Health Care—Is This the Right Time for Warfarin?

Co-Existent Pseudoxanthoma Elasticum and Vitamin K-Dependent Coagulation Factor Deficiency: Compound Heterozygosity for Mutations in the GGCX Gene

Pseudoxanthoma elasticum (PXE) is a multisystem disorder characterized by ectopic mineralization of connective tissues with primary manifestations in the skin, eyes, and cardiovascular system. The classic forms of PXE are due to mutations in the ABCC6 gene that encodes the ABCC6 protein, a putative transmembrane transporter expressed primarily in the liver and the kidneys. PXE-like clinical findings have been encountered in association with vitamin K-dependent coagulation factor deficiency, an autosomal recessive disorder that is due to mutations in either the GGCX or VKORC1 genes. In this study, we investigated a family with two siblings with characteristic features of PXE and vitamin K-dependent coagulation factor deficiency. Mutation analysis identified two GGCX mutations in the affected individuals (p. R83W and p.Q374X); however, no mutations in either ABCC6 or VKORC1 could be found. GGCX encodes a gamma-glutamyl carboxylase necessary for activation of both coagulation factors in the liver and matrix gla protein, which, in fully carboxylated form, is able to prevent ectopic mineralization. Analysis of skin by specific antibodies demonstrated that matrix gla protein was found predominantly in undercarboxylated form and was associated with the mineralized areas in the patients' lesional skin. These observations pathomechanistically suggest that, in our patients, reduced carboxylase activity results in a reduction of matrix gla protein carboxylation, thus allowing peripheral mineralization to occur. Our findings also confirm GGCX as the second gene locus causing PXE.

Late vitamin K deficiency bleeding after intramuscular prophylaxis at birth: a case report

We report the case of a 6-week-old female who presented an intracranial hemorrhage due to late vitamin K deficiency bleeding (VKDB). No other evident bleeding sites were present at the moment of diagnosis. Intramuscular vitamin K (1 mg) was administered at birth. She was exclusively breast-fed. No other risk factors for VKDB were detected. Low levels of vitamin K-dependent coagulation factors and their normalization after vitamin K administration confirmed the diagnosis of late VKDB. The present case suggests potential risks related to a single dose of intramuscular vitamin K at birth.