Trisomy X conferring moderate hemophilia A by extremely skewed X-chromosome inactivation.

Background: Hemophilia carriers occasionally present with bleeding tendency due to skewed inactivation of normal F8 carrying X chromosome. Key Clinical Question: Can extreme skewing of X-chromosome inactivation (XCI) with trisomy X cause low factor (F) VIII activity and bleeding in a hemophilia carrier?. Clinical Approach: A young female with low FVIII activity (2 IU/dL), who presented with history of frequent bleeding and F8 variant, NP_000123.1:p.(Arg1800His), was identified. The mother was also confirmed genetically as hemophilia carrier. Karyotype was 47, XXX, multiplex ligation-dependent probe amplification for aneuploidy in the family identified trisomy X only in the index case. Digital polymerase chain reaction using leucocytes, urine, and oral mucosa identified one maternal F8 variant carrying and 2 wild-type F8 carrying X chromosomes, but it detected no somatic mosaicisms. Methylation-sensitive-HpaII-polymerase chain reaction assay showed predominantly activated maternal and 2 fully inactivated paternal X chromosomes. The XCI patterns using tissues of different developmental origins showed extremely skewed XCI. Conclusion: Extreme skewing of XCI can occur even in hemophilia carriers with trisomy X, conferring frequent bleeding and low FVIII activity.

Comprehensive comparison of global coagulation assays to differentiate lupus anticoagulant from acquired hemophilia A in patients with prolonged APTT.

There is no established method for differentiating acquired hemophilia A (AHA) from lupus anticoagulant (LA) positivity because both present with prolonged activated partial thromboplastin time. We compared various parameters of rotational thromboelastometry (ROTEM), thrombin generation assay (TGA), and clot waveform analysis (CWA) in patients with AHA (n = 10) and LA (n = 44). Compared with AHA, possible (n = 12) and definite (n = 32) LA showed significantly shorter clotting time (CT) in NATEM mode of ROTEM (> 3600 vs. 501/533). In TGA, peak height was significantly lower in AHA (16 vs. 242/174 nM). In CWA, CT was significantly longer (81 vs. 36/41 s) and Ad|min1| was lower (2.1 vs. 8.7/6.7) in AHA. Notably, CT by NATEM and peak height in TGA completely discriminated between AHA and LA, whereas Ad|min1| did not discriminate between them in 4 cases of AHA and 1 of LA. Comparison of 3 patients with both AHA and LA against a patient with only LA and markedly low FVIII activity (3.5%) showed that both CT by NATEM and peak height of TGA precisely classified the former 3 cases as AHA and the latter 1 case as LA, whereas Ad|min1| classified all 4 cases as AHA. ROTEM and TGA can comparably distinguish between AHA and LA.

In vitro validation of chromogenic substrate assay for evaluation of surrogate FVIII-activity of emicizumab.

[Introduction] Emicizumab, a bispecific antibody mimicking activated factor VIII (FVIII), is increasingly used in prophylaxis against bleeding in hemophilia A. Human factor-based chromogenic substrate assay (hCSA) shows concentration-dependency between emicizumab and reported FVIII activity. However, the assay measurement settings have not been optimized for emicizumab, and the reported FVIII activity cannot be directly referred as surrogate FVIII activity. [Materials and Methods] For in vitro validation of hCSA-reported surrogate FVIII activity, we compared the equation curves for emicizumab concentration with surrogate FVIII activity using spiked plasma in the thrombin generation assay (TGA), hCSA, and clot waveform analysis (CWA). Then, we generated conversion equations for hCSA-reported surrogate FVIII value to that of TGA. We also assessed the additive effect of rFVIII onto 340 nM (i.e., 50 µg/mL) emicizumab using the same assays. [Results] With 1:20 diluted plasma, halving hCSA-reported surrogate FVIII activity can be approximated to that in TGA triggered by the extrinsic pathway reagent (27.3 IU/dL vs. 13.9 IU/dL) under therapeutic emicizumab concentration. Both in TGA and hCSA, the additive effect of added FVIII on therapeutic emicizumab concentration (340 nM) was maintained at low levels of FVIII but gradually decreased at higher levels. [Conclusions] Surrogate FVIII activity can be estimated simply by halving hCSA-reported FVIII value, and the additive effect of FVIII on emicizumab diminishes at high concentrations. Based on our in vitro study, a clinical study is currently being conducted to compare individual variation of surrogate FVIII activity in hCSA and TGA.

Clinical conditions and risk factors for inhibitor-development in patients with haemophilia: A decade-long prospective cohort study in Japan, J-HIS2 (Japan Hemophilia Inhibitor Study 2).

BACKGROUND: Inhibitor-development is a serious complication in patients with haemophilia (PwH). Previous studies reported that therapeutic and genetic factors could be associated with these alloantibodies. Relevant clinical features such as genetic-background and different treatment regimens in Japan remain unclear, however. AIMS: To analyse a nation-wide Japanese registry for PwH, and to examine risk factors for inhibitor-development. METHODS AND RESULTS: Newly diagnosed patients with haemophilia A (PwHA) or haemophilia B (PwHB) without inhibitors after 2007, and with treatment records traceable from 0 to 75 exposure days (ED), were enrolled in the Japan Hemophilia Inhibitor Study 2 (J-HIS2) initiated in 2008. Of 417 patients (340 PwHA, 77 PwHB) from 46 facilities, 83 (76 PwHA, 7 PwHB) were recorded with inhibitors by July 2020. Inhibitors were observed in 31.0% of severe PwHA, 8.0% moderate and 1.6% mild and in 17.1% of severe PwHB. The majority of inhibitors (89.7% in severe PwHA and 71.4% in severe PwHB) were detected on or before 25ED (median 12ED in PwHA and 19ED in PwHB). Genotyping in these severe patients identified an association between inhibitor-development and null variants of F8 (P < .01) or F9 (P < .05). A lower incidence of inhibitors was recorded in severe PwHA treated with prophylaxis than in those treated on-demand (P < .01). A past-history of intracranial-haemorrhage appeared to be associated with inhibitor-development, while FVIII-concentrates infusion and routine vaccination on the same day was not related to inhibitor-development. CONCLUSION: The J-HIS2 study has identified significant clinical variables associated with inhibitor-development in Japanese PwH, consistent with other global studies.

Combination therapy with von Willebrand factor concentrate plus recombinant factor VIII during cesarean section in a patient with type 3 von Willebrand disease and a low inhibitor titer: a case report.

Type 3 von Willebrand disease (VWD), a rare and severe subtype, can produce inhibitors in roughly 5% to 10% of cases. We present a case of type 3 VWD with inhibitors in late pregnancy, which was successfully managed with a combination of neutralization and factor (F)VIII replacement during cesarean delivery. The patient, a 30-year-old woman, had no history of inhibitors despite over 100 exposures to VWF/FVIII. She developed inhibitors after 28 weeks of weekly pd VWF/FVIII prophylaxis for recurrent urolithiasis-associated hematuria during pregnancy. Genetic analysis detected two novel frameshift mutations: VWF Exon7 c.777_784dup and Exon14 c.1625_1646del. Titers of inhibitors to factors VIII and VWF using the Bethesda assay were 1.2 and 1.1 BU/mL, respectively. Pharmacokinetics revealed significantly low in vivo recovery of FVIII:C and VWF:Rcof and shortened half-life. During cesarean delivery, a combination of bolus pd VWF/FVIII once daily for neutralizing inhibitors plus continuous infusion of recombinant FVIII Fc fusion protein resulted in minimal bleeding without allergic reactions. Both VWF:Rcof and FVIII:C levels increased transiently during the 7-h of combination therapy without thrombotic events. In conclusion, combination therapy with neutralization and continuous FVIII replacement was effective for hemostasis with a low VWD inhibitor titer, though further optimization is required.

Prolonged α-thrombin-related activation and delayed active protein C-associated degradation confer mild phenotype in a patient with severe hemophilia A with F8 p.H118R.

In hemophilia A, bleeding mostly correlates with factor VIII activity (FVIII:C), although some patients show discrepancy in bleeding severity and FVIII:C. We report a novel procoagulant mechanism associated with F8 p.H118R (c.353A > G) in a young Japanese man with few bleeding episodes despite low levels of FVIII:C (< 1 IU/dL). Plasma FVIII:C was < 1 IU/dL measured by one-stage clotting assay (OSA) and chromogenic substrate assay (CSA), whereas FVIII antigen (FVIII:Ag) was 9.7%. The global coagulation assay showed higher max speed in clot waveform analysis (CWA), shorter clotting time in rotation thromboelastometry (ROTEM) (1605 vs. > 5000 s), shorter lag time (4.87 vs. 12.47 min) and larger ETP (207.9 vs. 53.3 nM*min) in thrombin generation assay, compared with FVIII-deficient control. Expressed recombinant H118R mutant in culture media showed low FVIII:C (1-5 IU/dL) by OSA, with non-hemophilia level of FVIII:Ag. Western blot analysis using recombinant H118R showed longer persistence of heavy-chain of H118R after incubation with α-thrombin, compared with wild-type. Incubation of H118R with activated protein C (APC) also showed longer persistence of A1-A2 domain. In conclusion, H118R showed prolonged activation by α-thrombin and delayed APC-related FVIII degradation. These properties may confer the procoagulant activity and few bleeding episodes despite low FVIII:C.

[Examination of the effect of immunosuppressive therapy on acquired hemophilia A in elderly patients with bloodstream infections].

AIM: Acquired hemophilia A (AHA) is an acquired autoantibody (inhibitor) against blood coagulation factor VIII (FVIII) that significantly reduces FVIII activity and causes a bleeding tendency. Immune acquired coagulation factor deficiency. The peak age of onset is in the 70s. In Japan, which has an aging society, the number of reports has recently been increasing, and it should be noted that AHA is a bleeding disease that can occur in the elderly. Examined 5 cases of AHA that were experienced in our hospital. The FVIII inhibitor level, APTT, underlying disease, treatment history, and outcome were retrospectively examined using medical records. RESULTS: The age of onset was 76-93 years. At the time of diagnosis, the Hb (mg/dL) value was 6.1-10.3, the APTT was 75.6-203.2 seconds, the FVIII inhibitor value (BU/mL) was 18-686, and the platelet count was within the normal range in all cases. Bleeding control was possible using a bypass hemostatic agent in 4 patients. All patients underwent immunosuppressive therapy. Two patients were discharged alive and 3 patients died. The cause of death was infectious disease in all cases. The total prednisolone-equivalent dose of the deceased patients was 1,240-3,206 mg; one patient was treated with cyclophosphamide and was treated with dexamethasone. CONCLUSION: Long-term immunosuppressive therapy is expected to increase the risk of infection in elderly patients. The risk assessment of AHA treatment-related bloodstream infections is insufficient, and it will be necessary to accumulate data and consider appropriate assessments and countermeasures.

Coagulation assay discrepancies in Japanese patients with non-severe hemophilia A.

Patients with non-severe hemophilia A often show discrepancies in factor VIII (FVIII) activity. However, information on variant-specific coagulation assay characteristics in Japanese patients is limited. Pathogenic variants were classified into three groups, thrombin-cleavage site (TC), A1-A2-A3 interface (IF), and non-discrepant, with reference to previous studies. Cutoff values for the one-stage assay (OSA)/chromogenic substrate assay (CSA) ratio, which is suitable for distinguishing discrepancies, were determined for all five aPTT reagents. TGA and CWA parameters and bleeding scores were compared between groups. Two of the 39 patients with non-severe hemophilia A (5%) were classified as TC, 10 (26%) as IF, and 27 (69%) as non-discrepant. The OSA/CSA cutoff values between the groups varied widely by aPTT reagent and tended to be relatively low compared to previous studies. As an indicator of bleeding tendency, TGA had a low correlation coefficient for the IF variant, but this was not significant and was comparable to FVIII activity and CWA. Moreover, various parameters and bleeding tendency differed among patients with the same variants. Thus, our findings suggest that it is difficult to adequately assess the bleeding tendency of individual patients, even with the various assessments currently available.

Genetic analysis of carrier status in female members of Japanese hemophilia families.

BACKGROUND: Genetic characteristics and genetic carrier diagnosis in Japanese hemophilia female carriers have not been evaluated. OBJECTIVES: To provide genetic information on Japanese hemophilia female carriers and demonstrate the advantages of genetic testing in carrier diagnosis. METHODS: DNA sequencing combined with long polymerase chain reaction for inversion and multiplex ligation-dependent probe amplification for large mutations. RESULTS: Genetic analysis was performed in 69 male hemophiliac patients (48 hemophilia A [HA] and 21 hemophilia B [HB]) and 112 female family members (FFM) (80 from 50 families with HA and 32 from 22 families with HB). In 72 hemophiliac families, the identified F8 mutations were inversion (42%), missense (26%), and other variations (32%), while 74% of F9 mutations were point mutations. Among the 112 FFM, 53/80 (66%) with HA and 21/32 (66%) with HB were diagnosed genetically as carriers based on detection of heterozygous mutations. Low factor VIII activity (FVIII:C) levels (<50 IU/dL) were detected in only 10% of gene-confirmed carriers, suggesting that FVIII:C is not suitable for HA carrier prediction. Low FVIII/von Willebrand factor ratio (<0.9) was observed in 67% of gene-confirmed carriers. Half of the gene-confirmed HB carriers had low FIX:C (<60 IU/dL). Importantly, 32 mothers of 37 sporadic cases (86%) (24/27 [89%] HA and 8/10 [80%] HB) showed the relevant mutations, suggesting low incidence of de novo mutations in males. CONCLUSIONS: This study is the first to provide genetic information on Japanese hemophilia female carriers. Gene analysis is the gold standard for carrier diagnosis as it well identifies undetected female carriers based on pedigree information and hemostatic measurements.

Spectrum of F8 Genotype and Genetic Impact on Inhibitor Development in Patients with Hemophilia A from Multicenter Cohort Studies (J-HIS) in Japan.

Some genetic and treatment-related factors are risk factors for inhibitor development in patients with hemophilia A (PwHA). However, the genotype distribution of the factor VIII gene (F8) and genetic impact on inhibitor development in Japanese PwHA remain unknown. In 2007, the Japan Hemophilia Inhibitor Study 2 (J-HIS2) was organized to establish a nationwide registry system for hemophiliacs and to elucidate risk factors for inhibitor development, designed for prospective investigation following a retrospective study (J-HIS1) which had already finished. Patients, newly diagnosed after January 2007, were enrolled in J-HIS2 and followed up for inhibitor development and clinical environments since 2008 onward. In the present study, F8 genotypes of PwHA were investigated in the patients recruited from the J-HIS2 cohort as well as those with inhibitor from the J-HIS1 cohort. F8 variants identified in 59 PwHA with inhibitor in J-HIS1 were: 20 intron-22 inversions, 5 intron-1 inversions, 9 large deletions, 4 nonsense, 8 missense, 11 small in/del, and 2 splice-site variants. F8 variants identified in 267 (67 with inhibitor) PwHA in J-HIS2 were: 76(28) intron-22 inversions, 3(2) intron-1 inversion, 1(0) duplication, 8(5) large deletions, 21(7) nonsense, 109(7) missense, 40(11) small in/del, and 9(7) splice-site variants. Forty variants were novel. The cumulative inhibitor incidence rate in the severe group with null changes was 42.4% (95% confidence interval [CI]: 33.7-50.8), higher than that with nonnull changes (15.6% [95%CI: 6.8-27.8]), in J-HIS2. Relative risk for inhibitor development of null changes was 2.89. The spectrum of F8 genotype and genetic impact on inhibitor development in Japanese PwHA were consistent with the previous reports.

Successful Management of Acquired Factor V Inhibitor by Monitoring Factor V Activity, Antigen, and Inhibitor Values during Immunosuppressive Therapy.

Acquired factor V inhibitor (AFVI) results from the formation of autoantibodies to coagulation factor V (FV), and the clinical phenotype can range from asymptomatic laboratory abnormalities to life-threatening bleeds. We describe a 74-year-old man who developed AFVI along with a massive subcutaneous hematoma. He was initially treated with prednisolone (PSL), but AFVI recurred when the dose was reduced after a short period. We subsequently increased the PSL dose and added cyclophosphamide (CY), which resulted in a complete response. We then gradually tapered PSL and stopped CY, and the patient has since remained free of recurrent AFVI symptoms. We monitored FV activity, antigen concentrations, and inhibitor titers of this patient throughout the clinical course. The ratio of FV activity to antigen concentration was low at diagnosis and gradually increased along with the patient's improvement. This ratio might be a useful parameter for evaluating the effects of immunosuppressive therapy in patients with AFVI.

[Exhaustive analysis of genetic mutations associated with protein S deficiency utilizing next-generation sequencing analysis].

Protein S (PS) gene (PROS1) is found on chromosome 3 (3q11.1). To date, the reported detection rate of causative gene mutations in patients suspected of PS deficiency is only approximately 50%. To improve the detection rate of causative mutations, an exhaustive analysis of PROS1 was attempted using the next-generation sequencing method (NGS) to analyze the entire nucleotide sequence of PROS1 without analyzing those affected by pseudogenes. A total of 10 different mutations (three males and six females (52.9%) out of 17 patients (3 males and 14 females) with clinical PS deficiency were identified in this study. Remarkable improvements in the detection rate of causative mutations could not be obtained even with NGS analysis. These results suggested that the rate of diagnosis did not improve even after performing an exhaustive genetic analysis in patients clinically diagnosed with low PS antigen level and/or low PS activity. Although no reports were found on the gender gap in the rate of gene diagnosis for PS deficiency, the fluctuation of estrogen levels especially in women might cause a lower rate of diagnosis.

Emicizumab-mediated haemostatic function in patients with haemophilia A is down-regulated by activated protein C through inactivation of activated factor V.

Activated protein C (APC) inactivates activated factor V (FVa) and moderates FVIIIa by restricting FV cofactor function. Emicizumab is a humanized anti-FIXa/FX bispecific monoclonal antibody that mimicks FVIIIa cofactor function. In recent clinical trials in haemophilia A patients, once-weekly subcutaneous administration of emicizumab was remarkably effective in preventing bleeding events, but the mechanisms controlling the regulation of emicizumab-mediated haemostasis remain to be explored. We investigated the role of APC-mediated reactions in these circumstances. APC dose-dependently depressed thrombin generation (TG) initiated by emicizumab in FVIII-deficient plasmas, and in normal plasmas preincubated with an anti-FVIII antibody (FVIII-depleted). FVIIIa-independent FXa generation with emicizumab was not affected by the presence of APC, protein S and FV. The results suggested that APC-induced down-regulation of emicizumab-dependent TG was accomplished by direct inactivation of FVa. The addition of APC to emicizumab mixed with FVIII-depleted FV-deficient plasma in the presence of various concentrations of exogenous FV demonstrated similar attenuation of TG, irrespective of specific FV concentrations. Emicizumab-related TG in FVIII-depleted FVLeiden plasma was decreased by APC more than that observed with native FVLeiden plasma. The findings indicated that emicizumab-driven haemostasis was down regulated by APC-mediated FVa inactivation in plasma from haemophilia A patients without or with FV defects.

Identification of deep intronic individual variants in patients with hemophilia A by next-generation sequencing of the whole factor VIII gene.

BACKGROUND: No genetic defects are found in the coagulation factor VIII gene (F8) of approximately 2% of patients with hemophilia A. Recently, genomic variants causative of hemophilia A that were located deep within introns have been reported. OBJECTIVES: We aimed to establish a comprehensive method of analysis of F8 using next-generation sequencing (NGS) and investigate the variants located deep within the introns of F8. PATIENTS/METHODS: Forty-five male patients with hemophilia A, including 31 with previously identified causative mutations, were investigated. RESULTS: Our NGS analysis allowed for the identification of genetic variants in roughly 99% of F8. We confirmed that our NGS analysis can detect the single nucleotide variants and small deletions with high accuracy. After filtering, a total of 27 rare and unique individual variants from 16 patients remained. Three of these variants, c.144-10810T>C, c.1010-365A>G, and c.5219+9065A>G, were predicted as deleterious with high expected accuracy by PredictSNP2 analysis. We also predicted the impact on splicing by in silico analysis using three different algorithms. Two patients with unknown causative mutations carried unique individual variants, c.144-10810T>C and c.6723+193G>A. We inferred that the c.144-10810T>C variant likely causes hemophilia, while the effect of the c.6723+193G>A variant remains unclear. Our analysis showed that the c.6429+14194T>C variant was significantly detected in patients carrying the intron 22 inversion. CONCLUSIONS: Rare and unique individual variants located deep within the F8 introns in patients with hemophilia A are not uncommon. Future studies are necessary to determine the function and effect of these variants on F8 expression.

Genotyping analysis of the factor V Nara mutation, Hong Kong mutation, and 16 single-nucleotide polymorphisms, including the R2 haplotype, and the involvement of factor V activity in patients with recurrent miscarriage.

: Recurrent miscarriage can arise from a large diversity of causes and the factors responsible have not been fully clarified. The coagulation factor V R506Q (Leiden) mutation is a well known risk factor for recurrent miscarriage, although it has not been found in Japanese populations. We examined whether the factor V Nara and Hong Kong mutations, the factor V gene (F5) 16 single-nucleotide polymorphisms (SNPs), including the factor V R2 haplotype, and plasma factor V activity (FV:C) were risk factors for recurrent miscarriage. A cross-sectional study was conducted among 88 patients with a history of unexplained recurrent miscarriage and 95 fertile controls. None of the patients or controls was homozygous or heterozygous for the factor V Nara or Hong Kong mutation. In the 16 SNPs of F5, frequencies of the G/T and T/T genotypes at Ser156Ser were significantly lower in patients than in controls (OR 0.45, 95% CI 0.22-0.91, OR 0.32, 95% CI 0.14-0.72) and the allele frequency of C at Leu1288Leu was significantly higher in patients than that in controls (OR 1.66, 95% CI 1.02-2.71). The mean FV:C values were not significantly different between patients and controls. However, the prevalence of patients with a high or low FV:C (>95th or

Development of asymptomatic acquired factor V inhibitor after the administration of antibiotics.

Acquired factor V (FV) inhibitor is a rare coagulation disorder, the causes and clinical symptoms of which are known to vary widely. Acquired FV inhibitor mostly occurs with exposure to fibrin glues during surgical procedures. We experienced a case with asymptomatic acquired FV inhibitor caused by antibiotic therapy for aspiration pneumonia.A man in his eighties had been treated for chronic atrial fibrillation, cerebral infarction and spinal canal stenosis. He was admitted after antibiotic therapy for aspiration pneumonia in a previous hospital. On admission, the screening test for blood coagulation revealed extreme prolongation of both prothrombin time (PT) and activated partial thromboplastin time (APTT). Vitamin K was administered intravenously after cessation of warfarin, but neither PT nor APTT showed any improvement. Subsequently, a cross mixing test was performed and showed an inhibitor pattern. Furthermore, a high titer of FV inhibitor was detected by the Bethesda method and an acquired FV inhibitor was thus diagnosed. Despite the presence of FV inhibitor, the patient showed no bleeding symptoms. Eight months later, both PT and APTT had diminished to normal clotting time values without immunosuppressive therapies.

Factor X M402T: a homozygous missense mutation identified as the cause of cross-reacting material-reduced deficiency.

We investigated a mildly hemorrhagic patient with factor X (FX) deficiency to identify the nature of his defect by comprehensive analyses. A 42-year-old Japanese man was admitted to our hospital for uncontrolled gingival hemorrhage. His FX activity based on prothrombin time (PT) and activated partial thromboplastin time (aPTT) and FX antigen were <1, 6.5 and 11 %, respectively. A homozygous M402T missense mutation (c.1205 t>c; p.Met402Thr) was identified in the FX gene (F10) from both the patient and his brother. The mutation was not detected in the F10 of 82 unrelated normal Japanese individuals. We studied the functional consequences of this mutation by expressing mutant FX-M402T protein in HEK293 cells. This analysis revealed that the antigen of the FX-M402T mutants was approximately 26 % that of the wild-type FX in conditioned media. The FX-specific activity of FX-M402T mutants measured by a one-stage clotting assay based upon PT and aPTT, and a chromogenic assay using Russell's viper venom in the concentrated media was 7.7, 31.7, and 41.2 % of wild type, respectively. The results suggest that the mutation FX-M402T may cause a secretion defect and a molecular abnormality in FX.

Novel FV mutation (W1920R, FVNara) associated with serious deep vein thrombosis and more potent APC resistance relative to FVLeiden.

Factor V (FV) appears to be pivotal in both procoagulant and anticoagulant mechanisms. A novel homozygote (FVNara), a novel mechanism of thrombosis associated with Trp1920→Arg (W1920R), was found in a Japanese boy and was associated with serious deep vein thrombosis despite a low level of plasma FV activity (10 IU/dL). Activated partial thromboplastin time-based clotting assays and thrombin generation assays showed that FVNara was resistant to activated protein C (APC). Reduced susceptibility of FVaNara to APC-catalyzed inactivation and impaired APC cofactor activity of FVNara on APC-catalyzed FVIIIa inactivation contributed to the APC resistance (APCR). Mixtures of FV-deficient plasma and recombinant FV-W1920R confirmed that the mutation governed the APCR of FVNara. APC-catalyzed inactivation of FVa-W1920R was significantly weakened, by ~11- and ~4.5-fold, compared with that of FV-wild-type (WT) and FVLeiden (R506Q), respectively, through markedly delayed cleavage at Arg506 and little cleavage at Arg306, consistent with the significantly impaired APC-catalyzed inactivation. The rate of APC-catalyzed FVIIIa inactivation with FV-W1920R was similar to that without FV, suggesting a loss of APC cofactor activity. FV-W1920R bound to phospholipids, similar to FV-WT. In conclusion, relative to FVLeiden, the more potent APCR of FVNara resulted from significant loss of FVa susceptibility to APC and APC cofactor activity, mediated by possible failure of interaction with APC and/or protein S.

[Status of use and side effects of atovaquone for the treatment and prevention of pneumocystis pneumonia in HIV infected patients in Japan--from 1997 to 2012--The Clinical Study Group for AIDS Drugs, supported by Health and Labor Science Grants from the Ministry of Health, Labor and Welfare, Japan].

PURPOSE: Atovaquone is effective and well-tolerated for the treatment of mild or moderate Pneumocystis pneumonia (PCP) and the prevention of PCP. When atovaquone was not yet approved in Japan, it was supplied by the Clinical Study Group for AIDS Drugs, which has been supported by the Japan Health Science Foundation since 1997. We investigated the status of use and the reported side effects, since atovaquone has recently been approved and made available in Japan. METHOD: We retrospectively examined the application and adverse events associated with atovaquone use between January 1997 and March 2012. RESULTS: During this period, there were 721 new applications, increasing over time, with the highest rate of increase observed in recent years. Fifty-seven adverse events in 39 patients were reported. Drug eruption was the most common side effect (20 cases), followed by cytopenia (11 cases), fever (10 cases), and liver dysfunction (8 cases). Two deaths were reported (one with an unknown correlation, another with no comments provided). One case of liver dysfunction attributable to atovaquone was severe. In this case, the AST and ALT levels increased to 1,921 IU/L, and 1,062 IU/L, respectively on day 4 of atovaquone administration, but these levels improved after atovaquone discontinuation. No other severe side effects were reported. DISCUSSION: This study revealed that as in other countries, few side effects caused by atovaquone were reported in Japan. Moreover, there were no side effects unique to the Japanese population. However, caution is required when administering atovaquone, because a low incidence of severe atovaquone-induced liver dysfunction has been reported.