Important roles of the human leukocyte antigen class I and II molecules and their associated genes in the autoimmune coagulation factor XIII deficiency via whole-exome sequencing analysis.

Autoimmune coagulation factor XIII deficiency is a bleeding disorder caused by the formation of autoantibodies against the coagulation factor XIII (FXIII); however, the molecular mechanism underlying this process is unknown. Therefore, in the present study, we aimed to elucidate this mechanism by performing whole-exome sequencing analysis of 20 cases of autoimmune FXIII deficiency. We identified approximately 21,788-23,916 variants in each case. In addition to their ability to activate T cells, present antigens, and immune tolerance, the candidate alleles were further narrowed down according to their allelic frequencies and the magnitude of damage caused by the substitution of amino acids. After selecting 44 candidate alleles, we investigated whether they were associated with the FXIII inhibitory titers and/or the anti-FXIII autoantibodies. We found that two polymorphisms whose variant allele frequencies were significantly lower in the patients tended to decrease FXIII inhibitory titers as the number of variant alleles increased. We also found that five polymorphisms whose variant allele frequencies were significantly higher in the patients tended to increase the levels of the anti-FXIII autoantibodies as the number of variant alleles increased. All of these polymorphisms were found in the human leukocyte antigen (HLA) class I and II molecules and their associated genes. In particular, the HLA class II molecule and its associated genes were found to be involved in the presentation of foreign antigens as well as the negative regulation of the proliferation of T-cells and the release of cytokines. Polymorphisms in the HLA class II molecules and the cytotoxic T lymphocyte antigen 4 have been reported to be associated with the development of autoantibodies in acquired hemophilia A. Therefore, we hypothesized that these polymorphisms may be associated with the development of autoantibodies in autoimmune FXIII deficiency.

Acquired factor XIII deficiency: A review.

Acquired factor XIII (FXIII) deficiency is a rare bleeding disorder that can manifest with spontaneous or delayed life-threatening hemorrhage. Causes of acquired deficiency include immune-mediated inhibition, as well as non-immune FXIII hyperconsumption or hyposynthesis. The occurrence of acquired FXIII deficiency can be idiopathic or may be associated with comorbidities, such as malignancies or autoimmune disorders. Recognition of acquired FXIII deficiency and its underlying cause is imperative, as treatment options vary depending on the etiology. Diagnosis requires quantitative FXIII testing in addition to supplemental inhibitor studies if the clinical situation suggests an immune-mediated pathophysiology. Treatment may involve FXIII replacement, antifibrinolytic administration, and/or inhibitor eradication. However, treatment targets and thresholds are undefined in acquired FXIII deficiency. This review will focus on the clinical characteristics, diagnostic issues and therapeutic options for both immune and non-immune acquired FXIII deficiency. Cases are described to illustrate the clinical features of acquired FXIII deficiency.

Acquired Factor Xiii Deficiency: An Uncommon But Easily Missed Cause Of Severe Bleeding

Factor XIII (FXIII) is a plasma clotting protein involved in clot stabilization. Severe FXIII deficiency may present with severe, even fatal bleeding. Critically however, routine coagulation assays may be normal and only specific FXIII assays will detect the abnormality. Herein we discuss a case report of a patient with acquired FXIII deficiency in order to highlight the clinical challenges associated with establishing the diagnosis and discuss the treatment approach. A 70-year-old man presented with a gluteal haematoma despite no preceding personal history of bleeding. Extensive initial haemostatic investigations were normal until a specific FXIII assay showed a marked reduction in FXIII levels. With directed treatment, bleeding episodes ceased and remission was achieved. Clinical awareness of FXIII deficiency is important, so appropriate testing can be implemented in patients with unexplained bleeding diatheses, particularly those in whom bleeding responds poorly to standard replacement therapy.

Treatment of an acquired Factor XIII inhibitor in an adolescent with systemic lupus erythematosus and renal failure.

BACKGROUND: Factor (F)XIII deficiency is a rare inherited bleeding disorder, but can also be acquired due to the development of inhibitors. CASE REPORT: A 17-year-old female with systemic lupus erythematosus and end-stage kidney disease secondary to Class IV lupus nephritis developed spontaneous subcutaneous and muscular hematomas and delayed major bleeding after invasive procedures. She had abnormal kaolin thromboelastography (kTEG; decreased maximal amplitude, representative of clot strength) initially attributed to thrombocytopenia and uremic platelet dysfunction, but her FXIII activity was undetectable, and a high-titer antibody against FXIII was identified. She had improvement in clinical bleeding and in kaolin thromboelastogram result and transient improvement in FXIII activity after each dose of plasma-derived FXIII concentrate (Corifact) or cryoprecipitate. Her inhibitor titers gradually improved with multiple immunosuppressive therapies and plasma exchange. While her FXIII activity level remained mildly decreased, she has not had additional significant bleeding. CONCLUSION: Treatment with either plasma-derived FXIII or cryoprecipitate is an effective treatment to normalize the kTEG variables and clinical bleeding diatheses associated with acquired FXIII inhibitors. Higher doses may be needed in patients with high-titer inhibitor.

Successful Management of a Patient with Autoimmune Hemorrhaphilia due to Anti-Factor XIII/13 Antibodies Complicated by Pulmonary Thromboembolism.

Autoimmune hemophilia-like disease (hemorrhaphilia) due to anti-factor XIII (FXIII) antibodies (AH13) is a very rare, life-threatening bleeding disorder. A 77-year-old woman developed macrohematuria and a right renal pelvic hematoma. The coagulation times were not prolonged, but FXIII activity and antigen levels were severely and moderately reduced to 9 and 29% of normal values, respectively. Accordingly, the FXIII-specific activity turned out to be low. FXIII inhibitor and anti-FXIII-A subunit autoantibodies were detected by a 1:1 crossmixing test and immunoblot and immunochromatographic assays. She was therefore diagnosed with "definite AH13" and treated with plasma-derived FXIII concentrates to arrest the hemorrhage. In addition to a highly compressed inferior vena cava by a huge renal pelvic hematoma, deep vein thrombosis (DVT) and pulmonary thromboembolism (PE) were identified by systemic computed tomography. The patient was immediately started on anticoagulation therapy with low-dose heparin. Emboli disappeared quickly, probably because under-crosslinked thrombi caused by severe FXIII deficiency are vulnerable to fibrinolysis. After about 1.5 years, anti-FXIII-A subunit autoantibodies still remained despite the use of rituximab, steroid pulse therapy, oral prednisolone, and oral cyclophosphamide treatments. In conclusion, an extremely rare AH13 case complicated by DVT and PE was successfully managed by balancing anticoagulation therapy with hemostatic therapy.

Acquired Factor XIII inhibitor associated with mantle cell lymphoma.

BACKGROUND: Acquired Factor (F)XIII deficiency is a very rare bleeding diathesis with a potentially fatal outcome, previously described in the context of autoimmune disorders and leukemias. There is minimal information on autoantibody characterization and the role of antifibrinolytic therapy in patient management. CASE REPORT: A 79-year-old woman with a 3-month history of bruising and heavy menorrhagia presented with ongoing vaginal bleeding, symptomatic anemia, and a right thigh hematoma. Initial management included an axillary lymph node biopsy and coagulation evaluation. Pathologic examination of the biopsy specimen revealed mantle cell lymphoma. Clot solubility assay was consistent with a FXIII activity of less than 3%. An anti-FXIII inhibitor was suspected, the epitope specificity of which was mapped by micropeptide array analysis to regions in the ß-sandwich and catalytic core domain of the FXIII-A subunit. Management with cryoprecipitate, steroids, rituximab, and antifibrinolytic therapy resolved the bleeding diathesis and suppressed the inhibitor. CONCLUSION: This is the first reported case of an acquired FXIII inhibitor associated with mantle cell lymphoma in which the epitope specificity of the pathologic autoantibody was accurately defined. Antifibrinolytic therapy played a prominent role in the prevention of bleeding complications in the window period between initiation of immunosuppression and disappearance of the pathologic anti-FXIII autoantibody.

Non-autoimmune combined factor XIII A and B subunit deficiencies in rheumatoid arthritis patients treated with anti-interleukin-6 receptor monoclonal antibody (tocilizumab).

INTRODUCTION: Coagulation factor XIII (FXIII) is a plasma fibrin-stabilizing factor comprising A and B subunits (FXIII-A and FXIII-B, respectively) in the form of a heterotetramer (FXIII-A2B2). A humanized monoclonal antibody to the interleukin-6 receptor (tocilizumab, TCZ) has emerged as an effective treatment for rheumatoid arthritis (RA), because it drastically reduces the inflammation of RA. We previously reported that two TCZ-treated RA patients with acquired FXIII deficiency developed pelvic hemorrhage. METHODS: Because TCZ treatment had been shown to be related to low FXIII ammonia release activity and FXIII antigen in the two RA cases, we further examined FXIII-related parameters in 36 TCZ-treated RA patients and compared to 29 healthy controls by employing functional and immunologic assays for FXIII. RESULTS: FXIII-A antigen and FXIII amine incorporation and ammonia release activities were significantly lower in the TCZ-treated group than the control group. The TCZ-treated group also showed mildly low FXIII-A2B2 and FXIII-B levels, and their fibrinogen levels were the lower limit of normal. A significant correlation between FXIII-B and fibrinogen was observed in the control and the TCZ groups, suggesting a common metabolic mechanism(s) for these two hepatic proteins. Because the specific activities of FXIII were normal and neither anti-FXIII-A nor anti-FXIII-B antibody was detected, the overall low FXIII level may have resulted from its impaired synthesis under an unbalanced cytokine milieu caused by TCZ treatment. CONCLUSION: Concomitant deficiencies in multiple hemostatic factors, including FXIII, may lead to an increased risk for hemorrhage in TCZ-treated RA patients.

Acquired coagulation factor XIII deficiency: a case report.

The main objective of the study is to summarize the clinical characteristics of acquired factor XIII (FXIII) deficiency caused by a spontaneous FXIII inhibitor. Here we report a new case of acquired FXIII deficiency caused by FXIII inhibitor and review the medical literature regarding the characteristics and treatment of this disorder. FXIII deficiency caused by FXIII inhibitors is rare and of uncertain pathogenesis. Experience with therapeutic measures is limited to data from case reports. Immunosuppressive drugs may reduce autoantibodies or inhibit the cell clone generating the antibodies and may have been of benefit in our patient. The impact of such therapy on patient prognosis is incompletely known.

Rapid immunochromatographic test for detection of anti-factor XIII A subunit antibodies can diagnose 90 % of cases with autoimmune haemorrhaphilia XIII/13.

Autoimmune haemorrhaphilia XIII/13 (AH13) is an acquired life-threatening bleeding disorder due to anti-factor XIII (FXIII) autoantibodies (auto-Abs). AH13 patients may die of haemorrhage without correct diagnosis and proper treatment because of lack of awareness and the absence of rapid easy-to-use tests specific for this disease. Currently, the definitive diagnosis is established by cumbersome and time-consuming laboratory tests such as dot-blot assays and enzyme-linked immunosorbent assays (ELISA), and therefore these tests are generally not carried out. To save AH13 patients' lives, there is an urgent necessity for developing a rapid test for FXIII auto-Abs. We first generated and characterised mouse monoclonal antibodies (mAb) against human FXIII A subunit (FXIII-A), and then developed a rapid immunochromatographic test (ICT) for detection of anti-FXIII-A auto-Abs using one mAb with a dissociation constant of 9.3 × 10⁻¹¹ M. The auto-Ab-FXIII-A complex was captured by the mAb on a nitrocellulose membrane and visualised by Au-conjugated anti-human IgG Ab. Mixing with healthy control plasma improved the detection of auto-Abs in patients having extremely low levels of FXIII-A. The specificity and sensitivity of the ICT were 87 % and 94 %, respectively. We also detected auto-Abs against activated FXIII (FXIIIa) in three patients by pre-converting FXIII to FXIIIa by thrombin treatment. ICT values were significantly inversely correlated with FXIII activity levels, indicating an association between the quantity of anti-FXIII autoantibodies and AH13. This reliable rapid ICT assay can be applied to a point-of-care test to detect anti-FXIII-A auto-Abs, and will contribute to early diagnosis and treatment of AH13.

Report of a patient with chronic intractable autoimmune hemorrhaphilia due to anti-factor XIII/13 antibodies who died of hemorrhage after sustained clinical remission for 3 years.

Although the incidence of autoimmune hemorrhaphilia due to anti-Factor XIII (FXIII, not FVIII or FXII to avoid confusion) antibodies (AH13) or hemorrhagic "acquired FXIII deficiency due to anti-FXIII autoantibodies" was previously considered rare, it has been on the increase in the twenty-first century, at least in Japan. An 83-year-old woman with an unexplained hemorrhage was admitted to our hospital for intramuscular hematoma and severe anemia. Her FXIII activity was reduced to 10 % of normal; since FXIII inhibitors and anti-FXIII-A subunit autoantibodies were detected, she was definitively diagnosed with AH13. Despite developing cardiac tamponade due to pericardial hemorrhage, she clinically recovered from AH13 after hemostatic therapy with FXIII-concentrates and immunosuppressive treatment with rituximab and cyclophosphamide. However, her FXIII activity remained low and she died of hemorrhage 3.5 years after admission. AH13 patients should be monitored for a prolonged period, as this disease is very likely a chronic intractable hemorrhagic disorder.

Alloantibodies against the B subunit of plasma factor XIII developed in its congenital deficiency.

Factor XIII (FXIII) is a fibrin-stabilising factor consisting of catalytic A subunits (FXIII-A) and carrier B subunits (FXIII-B). FXIII-B prevents the fast clearance of FXIII-A from the circulation. Congenital FXIII-A deficiency is a rare bleeding disorder, and congenital FXIII-B deficiency is even rarer. Through our recent nationwide survey on "acquired haemophilia-like disease due to anti-FXIII autoantibodies," we newly diagnosed severe congenital FXIII-B deficiency in a Japanese man. He developed thrombocytopenia and gingival bleedings at the age of 73, and his FXIII activity was as low as 10% of the normal. When he suddenly developed spontaneous intramuscular haematoma, the bleeding was arrested by infusing FXIII concentrates. However, his FXIII activity remained around 10% of the normal. At the age of 74, ELISA and western blotting assay unexpectedly revealed complete absence of FXIII-B in the patient's plasma. A dot blot assay detected anti-FXIII-B alloantibodies for the first time in this disease, which could be attributed to the infusion of exogenous FXIII. He was found to be homozygous for a Japanese founder-effect mutation of F13B. Repeated infusions of exogenous FXIII for hemostasis increased anti-FXIII-B alloantibodies that resisted FXIII substitution. To the best knowledge of the authors, none of the remaining 10 reported cases of congenital FXIII-B deficiency developed alloantibodies to exogenous FXIII-B of plasma FXIII. An originally mild bleeding phenotype of severe congenital FXIII-B deficiency can be exaggerated by additional acquired conditions. Physicians should consider congenital FXIII-B deficiency when they encounter cases of unexplained bleeding disorders.

Aggressive fatal case of autoimmune hemorrhaphilia resulting from anti-Factor XIII antibodies.

Factor XIII (FXIII) is a fibrin-stabilizing factor consisting of catalytic A subunits (FXIII-A) and carrier B subunits (FXIII-B). Congenital FXIII deficiency is a rare bleeding disorder. Acquired FXIII deficiency resulting from FXIII hypo-synthesis and/or hyperconsumption is a relatively common disorder in which patients seldom bleed. On the contrary, 'autoimmune/acquired hemorrhaphilia XIII/13 due to anti-FXIII antibodies (AH13)' is a rare but life-threatening bleeding disorder. Through a nationwide survey of AH13, we diagnosed aggressive AH13 in a 66-year-old woman. She consulted our department because of a spontaneous hematoma in her hand. After 1.5 months, she also developed an intramuscular hematoma but retained approximately half (52%) of the normal FXIII activities. The patient's bleeding symptoms were aggravated to catastrophic massive bleedings in the large abdominal muscles and intrapelvic and intraperitoneal spaces. Two months after the bleeding onset, she died despite undergoing plasma exchange, which was performed because we were deeply suspicious of the presence of an anti-FXIII inhibitor. Seven days after her death, extremely low FXIII activity (6%) and positive data on anti-FXIII inhibitor were reported by a commercial laboratory. Our dot blot assay detected anti-FXIII-A autoantibodies, afterwards. Thus, the diagnosis of aggressive AH13 as early as possible is necessary to save patients' lives.

Acquired FXIII inhibitors: a systematic review.

Coagulation factor XIII (FXIII) is a protein that promotes fibrin stabilization by forming multiple covalent cross-links between fibrin monomers. Beside congenital FXIII deficiency, due to FXIII gene mutations, severe acquired FXIII deficiency has been described in association with autoantibodies against coagulation FXIII. These inhibitors, which occurs very rarely but may cause life-threatening bleeding complications, may arise spontaneously or in association with autoimmune and lymphoproliferative disorders or medications. The management of patients with acquired FXIII inhibitors is very demanding and treatment regimens must be focused on eradication of the inhibitor and to increase the plasma FXIII levels. In this systematic review, we analyse all the published case-reports on anti-FXIII autoantibodies focusing on the clinical features and treatment modalities of this acquired hemorrhagic condition.

Reduced difference of α2-plasmin inhibitor levels between plasma and serum in patients with severe factor XIII deficiency, including autoimmune hemorrhaphilia due to anti-factor XIII antibodies.

Coagulation factor XIII/13 (FXIII/13) stabilizes fibrin molecules by creating crosslinks with other fibrin molecules as well as with α2-plasmin inhibitor (α2-PI). "Hemorrhagic acquired FXIII/13 deficiency" was formerly considered rare, but has been increasing recently in Japan. During the 10 months of our nationwide campaign, we diagnosed five new patients with "acquired hemorrhaphilia due to anti-FXIII/13 autoantibodies," after examining 20 newly suspected cases of "hemorrhagic acquired FXIII/13 deficiency." When FXIII/13 activity was reduced to less than 50% of normal, it was proportional to the difference in α2-PI levels between plasma and serum (plasma-serum α2-PI), likely due to its cross-linking to fibrin by activated FXIII/13. Accordingly, decreased amounts of the plasma-serum α2-PI ex vivo may reflect reduced FXIII/13 activity in vivo. The plasma-serum α2-PI may thus also be a useful diagnostic marker for severe FXIII/13 deficiency.

Coagulation, an ancestral serine protease cascade, exerts a novel function in early immune defense.

Phylogenetically conserved serine protease cascades play an important role in invertebrate and vertebrate immunity. The mammalian coagulation system can be traced back some 400 million years and shares homology with ancestral serine proteinase cascades that are involved in, for example, Toll receptor signaling in insects and release of antimicrobial peptides during hemolymph clotting. In the present study, we show that the induction of coagulation by bacteria leads to immobilization and killing of Streptococcus pyogenes bacteria inside the clot. The entrapment is mediated via cross-linking of bacteria to fibrin fibers by the action of coagulation factor XIII (fXIII), an evolutionarily conserved transglutaminase. In a streptococcal skin infection model, fXIII(-/-) mice developed severe signs of pathologic inflammation at the local site of infection, and fXIII treatment of wild-type animals dampened bacterial dissemination during early infection. Bacterial killing and cross-linking to fibrin networks was also detected in tissue biopsies from patients with streptococcal necrotizing fasciitis, supporting the concept that coagulation is part of the early innate immune system.

Acquired factor XIII inhibitor: clinical features, treatment, fibrin structure and epitope determination.

Acquired factor XIII (FXIII) deficiency, arising from an autoantibody against factor XIII, is a rare bleeding disorder. This autoimmune disorder most commonly occurs in the elderly. Patients who develop such acquired FXIII inhibitors may present with catastrophic bleeding events and are hard to be diagnosed with the normal general coagulation tests. Though the disease is relatively rare, it is known to cause significant mortality. In this article we briefly describe a patient who presented with extensive bleeding and a normal activated partial thromboplastin time and prothrombin time (PT), but had an acquired inhibitor to FXIII; her primary disease was systemic lupus erythematosus (SLE). Also, we will focus on the clinical features, treatment modalities, fibrin structure and epitope identification for acquired factor XIII inhibitor with a review of the literature.