Acquired Factor X Deficiency in Patients With Primary Light Chain Amyloidosis.

Acquired factor X (FX) deficiency is a rare but serious complication of primary amyloidosis, presumably caused by the binding of amyloid proteins to the clotting factors. The prolonged prothrombin time, partial thromboplastin time, and low FX level, which are correctable by mixing study, are the disease hallmarks. An immediate goal of care is to stop bleeding. Clotting factor replacement requires close monitoring of coagulogram and FX levels due to varying FX clearance among patients. High-purity FX is currently approved for hereditary FX deficiency and has been successfully used in some acquired FX deficiency cases. Ongoing bleeding risk complicates the treatment decision. Novel therapies yielding rapid and deep response reduce amyloid protein production and improve long-term outcome.

Acquired factor X deficiency in light-chain (AL) amyloidosis is rare and associated with advanced disease.

INTRODUCTION: Systemic light chain (AL) amyloidosis can lead to an acquired coagulopathy secondary to acquired factor X (aFX) deficiency. However, it is not very clear who develops aFX deficiency in AL amyloidosis. METHODS: We therefore undertook this single centre, retrospective study to better characterize AL amyloidosis-associated aFX deficiency. RESULTS: Out of 121 AL patients who had FX testing at the time of their first evaluation at our institution, including 17 patients on warfarin at the time of testing, 10 out of 104 patients (9.6%) with systemic AL amyloidosis were found to have FX levels below 50%. Acquired FX deficiency was associated with advanced stage of AL amyloidosis and elevated cardiac biomarkers. Lower FX activity, advanced stage, and cardiac involvement by disease were associated with higher hazard of death on univariate analysis. On multivariate analysis, stage of AL amyloidosis was the only significant predictor of survival. Median survival time of patients with FX deficiency was 9.3 months compared to 118.4 months in those without. CONCLUSIONS: We conclude that while aFX deficiency is rare in systemic AL amyloidosis, it is a marker of advanced disease.

Use of a High-Purity Factor X Concentrate in Turkish Subjects with Hereditary Factor X Deficiency: Post Hoc Cohort Subanalysis of a Phase 3 Study.

Hereditary factor X (FX) deficiency is a rare bleeding disorder more prevalent in countries with high rates of consanguineous marriage. In a prospective, open-label, multicenter phase 3 study, 25 IU/kg plasma-derived factor X (pdFX) was administered as on-demand treatment or short-term prophylaxis for 6 months to 2 years. In Turkish subjects (n=6), 60.7% of bleeds were minor. A mean of 1.03 infusions were used to treat each bleed, and mean total dose per bleed was 25.38 IU/kg. Turkish subjects rated pdFX efficacy as excellent or good for all 84 assessable bleeds; investigators judged overall pdFX efficacy to be excellent or good for all subjects. Turkish subjects had 51 adverse events; 96% with known severity were mild/moderate, and 1 (infusion-site pain) was possibly pdFX-related. These results demonstrate that 25 IU/kg pdFX is safe and effective in this Turkish cohort (ClinicalTrials.gov identifier: NCT00930176).

Efficacy, safety and pharmacokinetics of a new high-purity factor X concentrate in women and girls with hereditary factor X deficiency.

Essentials Plasma-derived factor X concentrate (pdFX) is used to treat hereditary factor X deficiency. pdFX pharmacokinetics, safety and efficacy were assessed in factor X-deficient women/girls. Treatment success rate was 98%; only 6 adverse events in 2 subjects were possibly pdFX related. On-demand pdFX 25 IU kg-1 was effective and safe in women/girls with factor X deficiency. SUMMARY: Background A high-purity, plasma-derived factor X concentrate (pdFX) has been approved for the treatment of hereditary FX deficiency, an autosomal recessive disorder. Objective To perform post hoc assessments of pdFX pharmacokinetics, safety and efficacy in women and girls with hereditary FX deficiency. Patients/Methods Subjects aged ≥ 12 years with moderate/severe FX deficiency (plasma FX activity of < 5 IU dL-1 ) received on-demand or preventive pdFX (25 IU kg-1 ) for ≤ 2 years. Results Of 16 enrolled subjects, 10 women and girls (aged 14-58 years [median, 25.5 years]) received 267 pdFX infusions. Mean monthly infusions per subject were higher among women and girls (2.48) than among men and boys (1.62). In women and girls, 132 assessable bleeding episodes (61 heavy menstrual bleeds, 47 joint bleeds, 15 muscle bleeds, and nine other bleeds) were treated with pdFX, with a 98% treatment success rate versus 100% in men and boys. Mean pdFX incremental recovery was similar in the two groups (2.05 IU dL-1 versus 1.91 IU dL-1 per IU kg-1 ), as was the mean half-life (29.3 h versus 29.5 h). Of 142 adverse events in women and girls, headache was the most common (12 events in six subjects). Six events (two infusion-site erythema, two fatigue, one back pain, one infusion-site pain) in two subjects were considered to be possibly pdFX-related. Following the trial, pdFX was used to successfully maintain hemostasis in two subjects undergoing obstetric delivery. Conclusions pdFX was well tolerated and effective in women and girls with FX deficiency. Although women and girls had different bleeding symptoms and sites than men and boys, their pdFX pharmacokinetic profile was comparable.

Posterior reversible encephalopathy syndrome following blood transfusion in a patient with factor X deficiency: Is it an unusual systemic manifestation of an adverse transfusion reaction?

Adverse neurological transfusion reactions including posterior reversible encephalopathy syndrome (PRES) following blood transfusion are rare. Our case an 18-year-female with known Factor X deficiency with menorrhagia developed severe hypertension, followed by generalised tonic clonic convulsions apparently after blood component transfusion. She had earlier received 4 units of red blood cells (RBC) for anaemia and 10 units of fresh frozen plasma (FFP) for menorrhagia (with prolonged PT and APTT) within short span of time at another hospital. There was no history of hypertension, convulsions, any cardiovascular, renal or neurological disease before transfusion. The clinical features and magnetic resonance imaging findings led to the diagnosis of PRES. Abnormal electroencephalogram and a hypercoagulable haemostatic profile on thromboelastography along with derangement in blood glucose and liver function tests were also observed. Patient responded well to the anticonvulsants and antihypertensive agents prescribed and was discharged in a stable condition. Our patient had a systemic transfusion reaction involving predominantly neurological system, however, cardiovascular, hepatic, haemostatic and endocrine systems were also affected. This case is unusual being the first report of PRES occurring in a patient with factor X deficiency presenting with an array of clinical and laboratory features which have not been reported in earlier studies involving PRES. Presumably the initial aggressive red cell transfusion to treat anaemia initiated the crisis and further large volumes of transfused FFP contributed to this adverse transfusion reaction in our case. Clinicians and Transfusion Medicine specialists should be aware about this uncommon clinical entity.

Factor X Friuli Coagulation Disorder: Almost 50 Years Later.

The story of factor X (FX) Friuli. Factor X Friuli was discovered in 1969 to 1970. However, the story of that disease was an international event since patients with this defect were studied in France and in Italy, and different diagnoses were reached-FVII; FX; combined prothrombin complex; and combined FII, FVII, and FX deficiencies. The diagnostic difficulties were due to the peculiar clotting pattern presented by these patients, namely, prolonged partial thromboplastin time, prolonged prothrombin time but normal Russell viper venom clotting time. Only suitable anti-FX antisera clarified the pattern. Altogether 12 homozygotes and 102 heterozygotes have been followed during 4 decades. Six homozygotes died, 2 of them due to HIV infection and 1 due to hepatitis B liver cirrhosis. The other 3 died of nontransfusion-related morbidity. Bleeding tendency has been moderate in agreement with the extrinsic or intrinsic system assay results-FX level of 4% to 5% is considered normal. Heterozygotes may present occasional bleeding manifestations usually during surgery or delivery. Molecular analysis have shown that the mutation responsible for the defect is a Pro343Ser substitution in exon 8. Chimeric FX Friuli mice have been useful in studying the effect of FX levels on embryonic or natal mortality of these animals. No new homozygote but several heterozygotes have been recently seen. The study of FX Friuli has revolutionized the diagnostic approach to FX deficiencies. The FX should be assayed by all assay systems. The FX Friuli has never been described in any other country, and all patients studied come from the Friuli Meduna River Valley.

Congenital FX Deficiency Rio Tercero: A New Heterozygous Missense Mutation (Cys241Gly) with a Potentiating Effect by a Polymorphism (c. 503-57C>T).

OBJECTIVE: The aim was to report a new family with congenital FX deficiency. PATIENTS AND METHODS: The proposita is a 41 year old female with a moderate bleeding tendency (easy bruising, menorrhagia). Parents were not consanguineous. Family history was positive for a mild bleeding tendency. RESULTS: Coagulation and genetics studies revealed that the proposita and two of her siblings were heterozygotes for a new mutation Cys241Gly in exon 6 but had different FX level (2-3% of normal in the proposita and about 50% in the two siblings. The same was true for one of her three children. The mother and the other two children of the proposita had also slightly decreased FX levels but no mutation. On the suspicion that the proposita was carrying another defect which had escaped the Sanger method, we carried out a whole exome analysis and discovered that the proposita and one of her siblings were also homozygous for a mutation of a known polymorphism (c.503-57C>T). The daughter of the proposita was instead, besides being a carrier of the missense new mutation Cys241Gly, heterozygous for the same polymorphism. The mother and two other daughters were also heterozygous for the polymorphism. There were no deletions or duplications. CONCLUSION: The polymorphism present in the family seems to be capable of potentiating the defect induced by the new mutation. This, safe for epigenetics phenomena, is the only possible explanation for the discrepancy found in the FX level between mother and daughter despite the fact that both carried the same new mutation.

Complex formation with pentraxin-2 regulates factor X plasma levels and macrophage interactions.

Recently, we have identified scavenger receptor class A member I (SR-AI) as a receptor for coagulation factor X (FX), mediating the formation of an FX reservoir at the macrophage surface. Here, we demonstrate that the FX/SR-AI-complex comprises a third protein, pentraxin-2 (PTX2). The presence of PTX2 is essential to prevent internalization of FX by SR-AI, and the presence of FX is needed to interfere with internalization of PTX2. Binding studies showed that FX, SR-AI, and PTX2 independently bind to each other (KD,app: 0.2-0.7 µM). Surprisingly, immunoprecipitation experiments revealed that FX and PTX2 circulate as a complex in plasma, and complex formation involves the FX activation peptide. No binding of PTX2 to other vitamin K-dependent proteins was observed. Short hairpin RNA-mediated inhibition of PTX2 levels in mice resulted not only in reduced levels of PTX2, but also in similarly reduced FX levels. Moreover, PTX2 and FX levels were correspondingly reduced in SR-AI-deficient mice. Analysis of 71 human plasma samples uncovered a strong correlation between FX and PTX2 plasma levels. Furthermore, plasma samples of patients with reduced FX levels (congenital/acquired FX deficiency or after anti-vitamin K treatment) were characterized by concomitantly decreased PTX2 levels. In conclusion, we identified PTX2 as a novel partner for FX, and both proteins cooperate to prevent their SR-AI-mediated uptake by macrophages. Interestingly, their respective plasma levels are interdependent. These findings seem of relevance in perspective of ongoing clinical trials, in which plasma depletion of PTX2 is used as a therapeutical approach in the management of systemic amyloidosis.

A family with factor X deficiency from Argentina: a compound heterozygosis because of the combination of a new mutation (Gln138Arg) with an already known one (Glu350Lys).

The objective was to investigate a family from Argentina. The proposita was a 51-year-old woman who had a moderate bleeding tendency. Some of her children showed a mild bleeding tendency. Her mother and the husband were asymptomatic. Clotting, immunological and molecular biology techniques were used. Partial thromboplastin, prothrombin, Russell Viper venom-clotting times were moderately prolonged in the proposita, whereas they were slightly prolonged in the children and in her mother. Factor X (FX) activity was about 2-3% of normal in all assay systems. FX antigen was less than 5%. Other clotting factors and platelet were normal. Genetic analysis showed a compound heterozygosis: combination of a 'new' mutation (Gln138Arg) with an already known mutation (Glu350Lys). The children had intermediate FX levels (35-63% of normal) and were carriers of one of the two mutations present in the proposita. This is the first observation of a FX deficiency in Argentina.

Diagnostic Error of a Patient with Combined Inherited Factor VII and Factor X Deficiency due to Accidental Ingestion of a Diphacinone Rodenticide.

BACKGROUND: To explore the characteristics of laboratory examination and confirm the diagnosis of a patient with combined inherited FVII and FX deficiency after he ingested diphacinone rodenticide accidentally. METHODS: The coagulant parameter screening tests and coagulation factor activities were tested many times in the patient due to accidental ingestion of a diphacinone rodenticide. After the patient was treated for more than one year, gene analysis of correlated coagulation factors was analyzed in the patient and other family members by DNA direct sequencing. 106 persons were selected as controls from routine health examinations. RESULTS: After the patient was admitted to hospital, routine coagulation screening tests revealed the prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT) and low levels of vitamin K-dependent coagulation factors (FII, FVII, FIX, FX) activity, which was 102.4 seconds, 88.5 seconds, 7%, 3%, 8%, and 2%, respectively. During more than one year of treatment, the value of PT and APTT still showed significantly prolonged activity and FVII and FX activity levels were about 5%. While FII and FIX activity levels were in the normal range after 12 weeks of treatment. Two homozygous mutations, g.11267C>T of F7 gene resulting in the substitution Arg277Cys and g.28139G>T of F10 gene leading to the substitution Val384Phe, were identified in the patient. The patient's parents and sister was heterozygous for Arg277Cys and Val384Phe mutations. FVII and FX antigen levels in the patient were 7% and 30%, respectively. CONCLUSIONS: There were many similarities in the characteristics of laboratory examination between combined inherited FVII and FX deficiency and acquired vitamin K deficiency. The best way to identify them was gene analysis.

Importance of pharmacokinetic studies in the management of acquired factor X deficiency.

Up to 14% of individuals with systemic AL amyloidosis develop acquired factor X deficiency, which occurs due to adsorption of factor X onto amyloid fibrils. Although baseline factor X levels are not predictive of bleeding risk in these patients, serious hemorrhagic complications can occur, particularly during invasive procedures. Optimal management strategies to attenuate bleeding risk in these patients are unknown. We describe our experience in the management of acquired factor X deficiency, secondary to systemic AL amyloidosis, in a case series of three patients who received prothrombin complex concentrates (PCCs) for treatment and prevention of bleeding events. We performed a retrospective review extracting information on baseline demographics, laboratory data, pharmacokinetic (PK) studies, and clinically documented bleeding events. Our case series demonstrates that individuals with acquired factor X deficiency secondary to amyloidosis have variable laboratory and clinical responses to PCCs. This is likely due to distinct amyloid loads and fibril sequences, leading to different binding avidities for factor X. Our data emphasize the importance of performing PK testing prior to any invasive procedures to determine the dose and frequency interval to achieve adequate factor X levels for hemostasis, given the variable response between individuals.

An acquired, calcium-dependent, factor X inhibitor.

Acquired factor X (FX) deficiency unrelated to amyloidosis is a rare disorder in which an anti-FX antibody is infrequently detected. A patient with severe bleeding due to a calcium ion-dependent anti-FX IgG antibody is described. The FX affinity purified IgG bound the light chain of FX, but not FX lacking its γ-carboxyglutamic acid domain, and binding was enhanced >1000-fold in the presence of calcium ions. The antibody also recognized prothrombin and factor VII with about 100-fold and 1000-fold lower affinity. Like a lupus anticoagulant, increasing concentrations of phospholipids in functional assays reduced the inhibitory activity of the antibody. The effect of these properties of the inhibitor on laboratory diagnostic studies is considered.

Six novel missense mutations causing factor X deficiency and application of thrombin generation test.

INTRODUCTION: Inherited factor X (FX) deficiency is a rare hemorrhagic condition characterized by a variable clinical presentation weakly correlating with laboratory phenotype and genotype. Thrombin generation test (TGT) offers potential clinical advantages in the evaluation of hypocoagulable states. MATERIALS AND METHODS: Five FX assays were performed using clotting, chromogenic and immunological methods. The factor X gene (F10) defects were analyzed by direct sequencing. Thrombin generation (TG) was measured using a standard procedure with commercial reagents at 1 pM and 5 pM of tissue factor (TF). The influence of contact activation on TG at the two TF concentrations was analyzed by the addition of corn trypsin inhibitor (CTI). RESULTS: Seven missense mutations were identified in the F10 of the four probands with FX deficiency, six of which (Ser425Pro, Ala-29Pro, Phe324Leu, Ala235Thr, Cys111Arg and Met362Thr) were novel and associated with type I FX deficiency. TG measurements at 1 pM TF need the addition of CTI in both healthy individuals and FX-deficient patients. TG parameters of ETP, Peak and Rate correlated well with the FX:C levels and the clinical expressions of the FX-deficient patients at 1 pM TF with CTI. There is a higher sensitivity for FX deficiency at 1 pM TF compared with 5 pM TF in FX-deficient patients. CONCLUSIONS: TGT may serve as a useful laboratory tool to assess the individual clinical manifestation of the patients with FX deficiency and 1 pM TF concentration in the presence of CTI is recommended.

The missense Thr211Pro mutation in the factor X activation peptide of a bleeding patient causes molecular defect in the clotting cascade.

Factor X (FX) is a vitamin K-dependent coagulation zymogen, which upon activation to factor Xa assembles into the prothrombinase complex to activate prothrombin to thrombin. FX can be activated by either factor VIIa-tissue factor or factor IXa-factor VIIIa in extrinsic and intrinsic pathways, respectively. In this study, we identified a bleeding patient with moderate FX deficiency who exhibits a clotting defect only in the intrinsic pathway. Exome sequencing revealed that the patient carries a novel homozygous missense mutation that results in substitution of Thr211 with Pro in the activation peptide of FX. Thr211 is the site of an O-linked glycosylation in the activation peptide of FX. We postulated that the lack of this post-translational modification specifically impacts the activation of FX by intrinsic Xase, thereby impairing thrombin generation in the subject. To test this hypothesis, we expressed both wild-type FX and FX containing this mutation in mammalian cells and following the purification of the zymogens to homogeneity characterized their properties in both purified and plasma-based assay systems. Analysis of the results suggests that Thr211 to Pro substitution renders the FX mutant a poor substrate for both physiological activators, however, at physiological concentration of the substrate, the clotting defect manifest itself only in the intrinsic pathway, thus explaining the bleeding phenotype for the patient carrying this mutation.

Successful liver transplantation for a child with life-threatening recurrent bleeding episodes due to congenital factor X deficiency: a case report.

Factor X (FX) deficiency is a rare, autosomal-recessive coagulation disorder. Diagnosis can be confirmed by a factor X assay. Although fresh frozen plasma and prothrombin complex concentrates have been used as a temporary treatment of bleeding symptoms and preparation for surgery, frequent transfusion has its risk and prothrombin complex is not available in Korea. We report the first pediatric case of successful liver transplantation for the correction of a severe congenital FX deficiency in a child with recurrent life-threatening hemorrhagic episodes.