Diagnosis and Treatment of Autoimmune Acquired Coagulation Factor Deficiencies: An Evidence-Based Review of Japanese Practice.

Among the acquired coagulation factor deficiencies, autoimmune coagulation factor deficiencies (AiCFD) are rare and result from autoantibody production against coagulation factors. In Japan, a nationwide survey on AiCFD has been conducted since 2009. Autoimmune factor XIII, factor VIII, von Willebrand factor, factor V, and factor X deficiencies (AiF13D, AiF8D, AiVWFD, AiF5D, and AiF10D, respectively) have been enacted as "designated intractable disease-282." The incidence of AiF8D, AiF13D, and AiF5D was 1.83, 0.044, and 0.038 per million people/year, respectively, whereas that of AiVWFD and AiF10D was not calculable owing to the small number of patients. AiF13D and AiF8D were often idiopathic, whereas AiVWFD was often associated with plasma cell neoplasms. Epistaxis was a characteristic symptom of AiVWFD, intramuscular bleeding was frequent in AiF13D and AiF8D, and subcutaneous bleeding (purpura) was frequent in AiF13D and AiF10D, although none were specific to any one disease. Differential diagnosis cannot be made based on bleeding symptoms alone; therefore, rapid and accurate testing is mandatory. Definitive diagnosis of AiCFD necessitates identifying the presence of coagulation factor "inhibitors" and/or "autoantibodies." Therefore, these tests should be performed upon unexplained severe acquired coagulation factor deficiencies. The mainstay of treatment for AiCFD was hemostatic therapy and autoantibody eradication therapy, which included the replacement of coagulation factors or "bypass" agents and administration of immunosuppressants. The rate of hemorrhagic death was high in AiF13D (13%), followed by AiF5D (7%) and Ai10D (5%); therefore, early diagnosis and optimal treatment are essential for AiCFDs. Given the unknown long-term prognosis, "intractable disease platform registries" have begun to accumulate in Japan.

[Coagulative complete remission following early gastric cancer resection in a patient with steroid-resistant acquired hemophilia A and nephrotic syndrome].

During laparoscopic cholecystectomy, an 89-year-old man was discovered to have a prolonged APTT. He was transferred to our hospital for a thorough examination because wound bleeding necessitated a reoperation. Based on coagulation factor VIII activity (FVIII:C) of 3.6% and FVIII inhibitor levels of 48.5 BU/ml, he was diagnosed with acquired hemophilia A (AHA). Due to concerns about his advanced age and postoperative infection, immunosuppressive therapy with prednisolone 0.5 mg/kg/day was initiated. His clinical course was favorable, except hemorrhagic shock caused by intramuscular hemorrhage on the right back, although low FVIII inhibitor levels persisted for more than a month; additionally, lower leg edema and increased urinary protein were also observed. He was diagnosed as with AHA and secondary nephrotic syndrome, possibly because of early gastric cancer. As a result, radical endoscopic submucosal dissection (ESD) was performed while a recombinant coagulation factor VIIa preparation was administered. AHA improved rapidly following ESD, and coagulative remission was achieved. Simultaneously, the nephrotic syndrome improved. Because the control of malignant tumors may improve the status of AHA, the timing of malignant tumor intervention must be considered considering the risk of bleeding and infection associated with immunosuppression.

Antibodies against Noncatalytic B Subunit of Factor XIII Inhibit Activation of Factor XIII and Fibrin Crosslinking.

BACKGROUND: Coagulation factor XIII (FXIII) is a proenzyme of plasma transglutaminase. It comprises two catalytic A subunits (FXIII-A) and two carrier B subunits (FXIII-B). We previously reported that alloantibodies against FXIII-B could promote FXIII clearance in a patient with congenital FXIII-B deficiency who had received infusions of plasma-derived human FXIII (A2B2 heterotetramer). OBJECTIVES: We aimed to investigate whether anti-FXIII-B antibodies affect the catalytic function of FXIII. METHODS: FXIII activation and fibrin crosslinking were examined in the presence of patient plasma, isolated patient IgG, or rat anti-FXIII-B monoclonal antibodies. RESULTS: Alloantibody levels were increased by repeated infusions of plasma-derived A2B2 heterotetramer, which enhanced binding to the functionally important FXIII-B sushi domains. The patient plasma strongly inhibited cleavage of the FXIII-A activation peptide, amine incorporation, and fibrin crosslinking in normal plasma. Furthermore, anti-FXIII-B alloantibodies blocked the formation of the complex of FXIII-B with FXIII-A, and fibrinogen. Rat monoclonal antibodies against the 10th sushi domain of FXIII-B inhibited the incorporation of FXIII-B to fibrin, FXIII activation (i.e., cleavage of FXIII-A activation peptide), and ultimately fibrin crosslinking in normal plasma, independent of their effect on heterotetramer assembly with FXIII-A. Alloantibody binding to the A2B2 heterotetramer blocked the access of thrombin to the FXIII-A cleavage site, as indicated by the reaction of the alloantibodies to the A2B2 heterotetramer and FXIII-B, but not to FXIII-A. CONCLUSION: Anti-FXIII-B antibodies binding to the A2B2 heterotetramer and FXIII-B inhibited FXIII activation and its crosslinking function despite being directed against its noncatalytic subunit (FXIII-B).

[Autoimmune coagulation factor V/5 deficiency during chronic disseminated intravascular coagulation].

Aortic regurgitation, a thoracoabdominal aortic aneurysm, chronic myeloid leukemia, and chronic kidney disease were all being treated at two hospitals for an 83-year-old man. He was admitted to the Department of Orthopedics at our hospital with a lumbar compression fracture. Later, he experienced melena, for which the Department of Internal Medicine was consulted. Due to the aberrant results of PT-INR (7.1) and a PTT > 200 seconds on a coagulation test, we suspected the presence of an autoimmune coagulation factor deficiency, and prednisolone immunosuppressive therapy medication was started right away. Due to a sharp decline in FV/5 activity, the presence of FV/5 inhibitors, and the presence of anti-FV/5 autoantibodies, a final diagnosis of autoimmune coagulation factor V (FV/5) deficiency was made. After the start of immunosuppressive therapy, the FV/5 inhibitor and anti-FV/5 autoantibodies disappeared, and the FV/5 activity progressively returned to normal. Disseminated intravascular coagulation-which may have been caused by a known aortic aneurysm-worsened while tapering off prednisolone. Due to the patient's advanced age and other problems, the aneurysm was extensive and inappropriate for surgical repair. The coagulation test findings improved gradually upon initiation of warfarin therapy. Herein, the patient had autoimmune FV/5 deficiency, a rare disorder that made diagnosis and therapy difficult because of the patient's several coexisting conditions.

Fatal acquired coagulation factor V deficiency after hepatectomy for advanced hepatocellular carcinoma as a possible immune checkpoint inhibitor-related adverse event: a case report.

BACKGROUND: Atezolizumab plus bevacizumab therapy was recently introduced as the first line for unresectable advanced hepatocellular carcinoma (HCC), but immune-related adverse events (IrAEs) due to atezolizumab are a great concern. Here, we report the case of a patient who developed fatal acquired coagulation factor deficiency after hepatectomy for HCC, treated with atezolizumab and bevacizumab before surgery. CASE PRESENTATION: A 70-year-old man received right trisegmentectomy of the liver with hepaticojejunostomy for advanced HCC with bile duct invasion, after atezolizumab and bevacizumab therapy. The patient suffered the sudden onset of severe multiple coagulation factor deficiency (II, V, VII, VIII, IX, X, XI and XII) immediately following reoperation for anastomotic leakage of hepaticojejunostomy, 7 days after hepatectomy. The coagulation factor deficiency did not reverse even with intensive treatment, and the patient died of uncontrollable bleeding 32 days after hepatectomy. An IrAE due to atezolizumab was suspected because the patient had developed the possible IrAE of enthesitis of the right gastrocnemius muscle before surgery, and specific inhibitors against factor V and anti-factor V autoantibodies were detected, leading to an ultimate diagnosis of autoimmune FV/5 deficiency (AiF5D). CONCLUSION: Severe acquired coagulopathy should be recognized as a possible life-threatening IrAE when using atezolizumab and bevacizumab for HCC.

Acquired von Willebrand Syndrome in a Patient with Multiple Comorbidities, Including MALT Lymphoma with IgA Monoclonal Gammopathy and Hyperviscosity Syndrome.

Acquired von Willebrand syndrome (aVWS) develops with various underlying diseases. We herein report an individual with aVWS associated with mucosa-associated lymphoid tissue lymphoma in the lungs complicated by hyperviscosity syndrome, Sjögren's syndrome, and hypothyroidism. This patient developed life-threatening hemorrhaging during a lung biopsy despite transfusion of concentrate of plasma-derived VWF/factor VIII. The use of rituximab caused remission of the lymphoma and hyperviscosity syndrome in parallel with the resolution of aVWS. Thus, lymphoma and hyperviscosity might result in aVWS. Invasive procedures with a risk of bleeding should be avoided in individuals with aVWS.

Acquired factor V inhibitor with erythema and eosinophilia in a patient with end-stage renal disease.

Autoimmune factor V deficiency (AiFVD) is a rare bleeding disorder caused by factor V inhibitors. In this report, we present the case of an 89-year-old man who developed bleeding tendency during surgery to create arteriovenous fistula for hemodialysis. The bleeding tendency developed with prolongation of activated partial thromboplastin and prothrombin time, following drug-induced eruption and eosinophilia. Significant reduction in coagulation factor activity and inhibitory pattern in cross-mixing tests suggested the presence of inhibitors to coagulation factors. Subsequently, we detected a factor V inhibitor and anti-factor V autoantibodies was confirmed using enzyme-linked immunosorbent assay with purified human plasma factor V. Thus, the patient was 'definitely diagnosed' with AiFVD in accordance with the diagnostic criteria enacted by the Japanese Ministry of Health, Labor, and Welfare. The bleeding tendency improved after initiating oral prednisolone 50 mg (1 mg/kg) followed by normalization of activated partial thromboplastin time and prothrombin time at the 34th day. After improving the coagulation system prolongation, the inhibitor and autoantibodies has been eradicated. Since it is suggested that drug-induced immune response can cause AiFVD, AiFVD should be considered in patients who undergo hemodialysis and develop failure of hemostasis and drug-induced eruption.

Identification of non-neutralizing anti-factor X autoantibodies in three Japanese cases of autoimmune acquired factor X deficiency.

INTRODUCTION: Autoimmune factor X (FX or F10) deficiency (AiF10D) is an extremely rare acquired haemorrhagic disorder characterized by a severe reduction in FX activity due to autoantibodies against FX. AIM: Anti-FX autoantibodies were investigated in four patients with suspected AiF10D, and their properties were analysed. METHODS AND RESULTS: Anti-FX auto antibodies in plasma were detected by ELISA with three of four cases. One case of anti-FX autoantibody negativity was later diagnosed as AL-amyloidosis. IgG1 and IgG3 coexisted in all anti-FX autoantibodies of the three patients with AiF10D (cases X1, X2, and X3). Western blot analysis showed that the antibodies were bound to the FX light chain for cases X2 and X3, but the binding was weak for case X1. When the fusion proteins of a secretory luciferase with full-length FX or its γ-carboxylated glutamic acid (Gla) domain were added to the plasma of the three patients, both fusion proteins were immunoprecipitated as antigen-antibody complexes. Contrarily, the latter fusion protein produced in the presence of warfarin demonstrated a decrease in the collection rate, suggesting that their autoantibodies recognized the light chain and regions containing Gla residues. Since all three patients were essentially negative for FX inhibitors, it was concluded that the anti-FX autoantibodies for these cases were predominantly non-neutralizing. The concentration of the FX antigen also significantly reduced in these patients, suggesting that anti-FX autoantibodies promote the clearance of FX. CONCLUSION: Immunological anti-FX autoantibody detection is highly recommended to ensure that AiF10D cases are not overlooked, and to start necessary immunosuppressive therapies.

A Review of Autoimmune Acquired von Willebrand Factor Deficiency in Japan.

von Willebrand factor (VWF) forms high-molecular-weight multimers and plays an essential role in hemostasis, and thus its deficiency leads to bleeding symptoms. Acquired von Willebrand syndrome (AVWS) is rare, but potentially underdiagnosed, and develops in various underlying disorders. AVWS caused by anti-VWF autoantibodies is a rare subcategory of AVWS that can also be referred to as autoimmune VWF deficiency (AiVWFD). We performed a search of patients with autoimmune coagulation factor deficiencies in our nationwide survey in Japan. Among these, suspected cases of AiVWFD were extremely few, with only 11 case consultations in the last 10 years. Of these, three and five were respectively positive for anti-VWF autoantibodies (anti-VWF-Ab) and VWF inhibitor (VWF-inh). We also performed an extensive literature search of other cases from Japan, and in total, 40 cases were finally identified to have AiVWFD, with mean age of 55.0 years. Most underlying disorders were lympho- or myeloproliferative diseases, followed by autoimmune diseases. The major bleeding sites were subcutaneous and mucosal, the bleeding severity was moderate, and there were no hemorrhagic deaths. Bleeding time was prolonged; factor VIII activity, VWF antigen, and VWF activity were decreased, and high-molecular-weight VWF multimers were absent or decreased. These are similar to the common abnormal laboratory findings observed among general AVWS cases. Hemostatic therapy often involved VWF concentrates and vasopressin, and antibody eradication therapy often included corticosteroids and achieved remission. Notably, of all cases, 68% had anti-VWF-Abs, and 83% of anti-VWF-Ab-positive patients were also VWF-inh positive. To accumulate precise clinical information on AiVWFD, it is necessary to verify and improve the measurement methods for both anti-VWF-Ab and anti-VWF-inh. These findings from Japan should be confirmed in other geographic localities.

Autoimmune Coagulation Factor X Deficiency as a Rare Acquired Hemorrhagic Disorder: A Literature Review.

Coagulation factor X (F10) amplifies the clotting reaction in the middle of the coagulation cascade, and thus F10 deficiency leads to a bleeding tendency. Isolated acquired F10 deficiency is widely recognized in patients with immunoglobulin light-chain amyloidosis or plasma cell dyscrasias. However, its occurrence as an autoimmune disorder is extremely rare. The Japanese Collaborative Research Group has been conducting a nationwide survey on autoimmune coagulation factor deficiencies (AiCFDs) starting in the last decade; we recently identified three patients with autoimmune F10 deficiency (AiF10D). Furthermore, an extensive literature search was performed, confirming 26 AiF10D and 28 possible cases. Our study revealed that AiF10D patients were younger than patients with other AiCFDs; AiF10D patients included children and were predominantly male. AiF10D was confirmed as a severe type of bleeding diathesis, although its mortality rate was not high. As AiF10D patients showed only low F10 inhibitor titers, they were considered to have nonneutralizing anti-F10 autoantibodies rather than their neutralizing counterparts. Accordingly, immunological anti-F10 antibody detection is highly recommended. Hemostatic and immunosuppressive therapies may help arrest bleeding and eliminate anti-F10 antibodies, leading to a high recovery rate. However, further investigation is necessary to understand the basic characteristics and proper management of AiF10D owing to the limited number of patients.

Factors associated with health intentions and behaviour among health checkup participants in Japan.

Health intentions and behaviours are essential for improving the health of individuals and society. This study used cross-sectional data from 20,155 health checkup participants in the Yamagata study to identify factors associated with health intentions and behaviours. Information regarding the current level of health intentions and behaviours was collected using a baseline survey questionnaire. Participants were categorised into three groups: having no intention (no intention), having intentions to improve but not acting on them (intention), and already active (action). The associations between background factors and the presence/absence of health intentions and behaviours were assessed using logistic regression analysis. Of the participants, 35.4%, 37.7%, and 26.9% belonged to the no intention, intention, and action groups, respectively. Multivariate analysis revealed that the factors associated with health intentions were being young, being female, longer duration of education, higher body mass index and abdominal circumference, diabetes, and dyslipidaemia. The factors associated with health behaviours were being older and male, not consuming alcohol, not smoking, performing daily exercise, and having diabetes. These results indicate that health guidance considering background factors, including age, gender, education, and comorbidities, may be useful for effectively promoting health intentions and health behaviours in the Japanese population.

Association between milk and yogurt intake and mortality: a community-based cohort study (Yamagata study).

BACKGROUND: Dairy products are known as health-promoting foods. This study prospectively examined the association between milk and yogurt intake and mortality in a community-based population. METHODS: The study population comprised of 14,264 subjects aged 40-74 years who participated in an annual health checkup. The frequency of yogurt and milk intake was categorized as none (< 1/month), low (< 1/week), moderate (1-6/week), and high (> 1/day) intake. The association between yogurt and milk intake and total, cardiovascular, and cancer-related mortalities was determined using the Cox proportional hazards model. RESULTS: During the follow-up period, there were 265 total deaths, 40 cardiovascular deaths and 90 cancer-related deaths. Kaplan-Meier analysis showed that the total mortality in high/moderate/low yogurt intake and moderate/low milk intake groups was lower than that in none group (log-rank, P < 0.01). In the multivariate Cox proportional hazard analysis adjusted for possible confounders, the hazard ratio (HR) for total mortality significantly decreased in high/moderate yogurt intake group (HR: 0.62, 95% confidence interval [CI]: 0.42-0.91 for high intake, HR: 0.70, 95%CI: 0.49-0.99 for moderate intake) and moderate milk intake group (HR: 0.67, 95% CI: 0.46-0.97) compared with the none yogurt and milk intake groups. A similar association was observed for cancer-related mortality, but not for cardiovascular mortality. CONCLUSIONS: Our study showed that yogurt and milk intake was independently associated with a decrease in total and cancer-related mortalities in the Japanese population.

Lobar Hemorrhage Induced by Acquired Factor XIII Deficiency in a Patient with Cerebral Amyloid Angiopathy.

A 68-year-old man presented with intracranial hemorrhage in the right frontal lobe, which rapidly increased the day after admission. We performed hematoma removal with a biopsy of the cortex around the hematoma. The day after the operation, a subcutaneous hematoma over the craniotomy appeared, and the computed tomography showed a recurrent hemorrhage with an acute subdural hematoma. We were aware of a bleeding tendency, and a detailed hematologic examination by hematologists revealed autoimmune acquired factor XIII deficiency due to an antifactor XIII antibody. Specimens taken around the hematomas were pathologically diagnosed as cerebral amyloid angiopathy (CAA) on immunohistochemical examination. We considered that acquired factor XIII deficiency had induced lobar hemorrhage in the frontal lobe affected with CAA, and the coagulation disorder induced postoperative rebleeding. The patient died from repeated lobar hemorrhage 3 years after the surgery. There is no routine screening coagulation test including the active partial thromboplastin time and the prothrombin time for factor XIII deficiency. It is important for neurologists and neurosurgeons to be aware of this rare disease in patients with a bleeding tendency.

Molecular pathogenesis of plasminogen Hakodate: the second Japanese family case of severe type I plasminogen deficiency manifested late-onset multi-organic chronic pseudomembranous mucositis.

A 64-year-old man first developed ligneous conjunctivitis at the age of 58 years after right pulmonary resection because of suspected cancer; otherwise, he had been healthy. Since then, he began to suffer from various forms of chronic pseudomembranous mucositis. Laboratory tests demonstrated that he had 7.8 % of plasminogen activity and 5.9 % of the normal antigen level. Thus, he was diagnosed as having severe type I plasminogen deficiency, making him the third case in Japan. DNA sequencing and PCR-restriction fragment length polymorphism analyses revealed that this patient was a compound heterozygote of a G-to-A missense mutation (G266E) in exon VIII and a g-to-a mutation at the obligatory splicing acceptor site in intron 12 (IVS12-1g>a). These two mutations were confirmed to be novel. Molecular modeling and splice site strength calculation predicted conformational disorder(s) for the Glu266 mutant and a drastic decrease in splicing efficiency for intron 12, respectively. Western blot analysis demonstrated that the patient contained a small amount of the normal-sized plasminogen protein. Mass spectrometric analysis of the patient's plasminogen revealed a peptide containing the wild-type Gly266 residue and no peptides with mutations at Glu266. However, he had never suffered from thrombosis. Low levels of fibrinogen/fibrin degradation products (FDP), D-dimer, and plasmin-α2-plasmin inhibitor complex clearly indicated a hypo-fibrinolytic condition. However, his plasma concentration of elastase-digested crosslinked FDPs was 4.8 U/mL, suggesting the presence of an on-going plasmin(ogen)-independent "alternative" fibrinolytic system, which may protect the patient from thrombosis. The patient has been free from recurrence of ligneous conjunctivitis for approximately 2.5 years.

Successful bypass surgery for esophageal carcinoma under adequate factor XIII/13 replacement therapy in a case of intractable autoimmune hemorrhaphilia due to anti-Factor XIII/13 antibodies.

Autoimmune hemorrhaphilia due to anti-factor XIII (FXIII) antibodies (AH13) is a life-threatening disease associated with high risk of surgical bleeding. Since AH13 occurs mainly in the elderly, patients of AH13 tend to be complicated with other life-threatening diseases that may require surgical procedures. During our nation-wide survey on AH13, supported by the Japanese Ministry of Health, Labor, and Welfare, patients with unexplained bleeding were examined for FXIII-related parameters and anti-FXIII autoantibodies. A 64-year-old man had previously been tentatively diagnosed with AH13 and received immunosuppressive therapies, as FXIII inhibitor was detected by functional cross-mixing studies. About 2 years later, he was definitively diagnosed with AH13, because our immuno-chromatographic test and enzyme-linked immuno-sorbent assay detected FXIII-bound anti-FXIII-A subunit autoantibodies. Since routine endoscopic examination revealed suspected esophageal carcinoma, a preparatory FXIII pharmacokinetic (PK) analysis was performed by infusing FXIII concentrates prior to biopsy. Consequently, biopsy of this lesion was done without bleeding complications. One month later, a second PK study was carried out before surgery, and esophageal bypass surgery was completed successfully under FXIII replacement therapy. Our experience with this case suggests that operations can be performed safely and with confidence even in patients with such life-threatening hemorrhagic diseases.

The plasma levels of protein Z-dependent protease inhibitor increase after gynecological surgery independently of estrogen.

INTRODUCTION: Protein Z (PZ)-dependent protease inhibitor (ZPI) is a serine protease inhibitor that efficiently inhibits activated factor X when ZPI is in complex with PZ. We previously reported significantly higher concentrations of plasma ZPI (and PZ) in women during normal pregnancy than in non-pregnant women. METHODS: We explored the possible contribution of estrogen to the ZPI levels in patients with or without bilateral oophorectomy (OVX), which induces artificial menopause where blood estrogen levels drastically decrease. One hundred ninety-one pre-menopausal Japanese women who underwent open hysterectomy owing to neoplasms participated in this study and were divided into two groups: 98 OVX and 93 Non-OVX cases. Plasma ZPI was measured by ELISA. RESULTS AND CONCLUSION: Contrary to our working hypothesis, plasma ZPI levels increased significantly in the OVX group after surgery when compared with the pre-operation levels. When these patients were individually analyzed, their ZPI value also rose significantly from pre-operation to post-operation levels. In contrast, plasma PZ levels remained unchanged. The significantly increased ZPI and unchanged PZ levels were also observed in the Non-OVX group. The increased ZPI levels were not significantly related to 17ß-estradiol, luteinizing hormone or follicular stimulating hormone levels, clearly indicating that estrogen did not contribute to the plasma ZPI concentrations. Typical acute phase reactants fibrinogen and C-reactive protein (CRP) were also significantly elevated after surgery in both OVX and Non-OVX groups. However, only weakly significant linear relationships were observed between ZPI and fibrinogen or CRP, indicating the presence of alternative regulatory mechanisms underlying their plasma concentrations.

The Non-catalytic B Subunit of Coagulation Factor XIII Accelerates Fibrin Cross-linking.

Covalent cross-linking of fibrin chains is required for stable blood clot formation, which is catalyzed by coagulation factor XIII (FXIII), a proenzyme of plasma transglutaminase consisting of catalytic A (FXIII-A) and non-catalytic B subunits (FXIII-B). Herein, we demonstrate that FXIII-B accelerates fibrin cross-linking. Depletion of FXIII-B from normal plasma supplemented with a physiological level of recombinant FXIII-A resulted in delayed fibrin cross-linking, reduced incorporation of FXIII-A into fibrin clots, and impaired activation peptide cleavage by thrombin; the addition of recombinant FXIII-B restored normal fibrin cross-linking, FXIII-A incorporation into fibrin clots, and activation peptide cleavage by thrombin. Immunoprecipitation with an anti-fibrinogen antibody revealed an interaction between the FXIII heterotetramer and fibrinogen mediated by FXIII-B and not FXIII-A. FXIII-B probably binds the γ-chain of fibrinogen with its D-domain, which is near the fibrin polymerization pockets, and dissociates from fibrin during or after cross-linking between γ-chains. Thus, FXIII-B plays important roles in the formation of a ternary complex between proenzyme FXIII, prosubstrate fibrinogen, and activator thrombin. Accordingly, congenital or acquired FXIII-B deficiency may result in increased bleeding tendency through impaired fibrin stabilization due to decreased FXIII-A activation by thrombin and secondary FXIII-A deficiency arising from enhanced circulatory clearance.

Clot retraction is mediated by factor XIII-dependent fibrin-αIIbß3-myosin axis in platelet sphingomyelin-rich membrane rafts.

Membrane rafts are spatially and functionally heterogenous in the cell membrane. We observed that lysenin-positive sphingomyelin (SM)-rich rafts are identified histochemically in the central region of adhered platelets where fibrin and myosin are colocalized on activation by thrombin. The clot retraction of SM-depleted platelets from SM synthase knockout mouse was delayed significantly, suggesting that platelet SM-rich rafts are involved in clot retraction. We found that fibrin converted by thrombin translocated immediately in platelet detergent-resistant membrane (DRM) rafts but that from Glanzmann's thrombasthenic platelets failed. The fibrinogen γ-chain C-terminal (residues 144-411) fusion protein translocated to platelet DRM rafts on thrombin activation, but its mutant that was replaced by A398A399 at factor XIII crosslinking sites (Q398Q399) was inhibited. Furthermore, fibrin translocation to DRM rafts was impaired in factor XIII A subunit-deficient mouse platelets, which show impaired clot retraction. In the cytoplasm, myosin translocated concomitantly with fibrin translocation into the DRM raft of thrombin-stimulated platelets. Furthermore, the disruption of SM-rich rafts by methyl-ß-cyclodextrin impaired myosin activation and clot retraction. Thus, we propose that clot retraction takes place in SM-rich rafts where a fibrin-αIIbß3-myosin complex is formed as a primary axis to promote platelet contraction.

Severe inhibitor-negative acquired factor XIII/13 deficiency with aggressive subdural haemorrhage.

Acquired factor XIII (FXIII) deficiency is a common disease and seldom causes bleeding. However, severe FXIII deficiency may result in life-threatening bleeding. Although the inhibitor against FXIII has recently been focused as the cause of haemorrhagic acquired FXIII deficiency, the pathophysiology of inhibitor-negative cases could also be involved. We report a case of an 85-year-old Japanese man with serious subdural haemorrhage showing a remarkable decreased level of FXIII activity. He also manifested complications of compensated disseminated intravascular coagulation (DIC) with chronic renal failure, abdominal aortic aneurysm (AAA) and right renal carcinoma. Despite the successful evacuation of the haemorrhage, acute subdural haemorrhage subsequently developed that necessitated further craniotomies. Plasma cross-mixing studies and dot blot assay revealed no inhibitors against FXIII. We speculated that the decreased FXIII activity could be mainly due to hyperconsumption by DIC and surgery. Because plasma-derived FXIII concentrates are available to stop bleeding, clinicians should be aware of severe acquired inhibitor-negative FXIII deficiency in cases of unexplained excessive bleeding.