Kazuya Sakai

Nara Medical University · Department of Blood Transfusion Medicine

Congenital thrombotic thrombocytopenic purpura is an autosomal recessive inherited disease with a clinically heterogeneous course and an incompletely understood genotype-phenotype correlation. In 2006, the Hereditary TTP Registry started recruitment for a study which aimed to improve the understanding of this ultra-rare disease. The objective of th...

von Willebrand factor (VWF) is a blood glycoprotein that plays an important role in platelet thrombus formation through interaction between its A1 domain and platelet glycoprotein Ib. ARC1779, an aptamer to the VWF A1 domain, was evaluated in a clinical trial for acquired thrombotic thrombocytopenic purpura (aTTP). Subsequently, caplacizumab, an an...

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune disorder caused by neutralizing anti-ADAMTS13 autoantibodies. In Caucasians, human leukocyte antigen (HLA) allele DRB1*11 was a predisposing factor for iTTP, while DRB1*04 was a protective factor. However, the role of HLA in Asians is unclear. In this study, we analyzed...

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal thrombotic microangiopathy caused by autoantibody-mediated severe deficiency of ADAMTS13. Standardized definitions of response, exacerbation, remission and relapse were initially proposed in 2003 and modified by the International Working Group (IWG) for TTP in 2017. T...

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is an ultra-rare thrombotic disease caused by autoantibody induced ADAMTS13 deficiency. Open ADAMST13 conformation, induced by autoantibodies, was identified as a novel biomarker for iTTP. Determining immunoprofiles in iTTP patients was shown to guide the development of novel targeted thera...

For patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP), caplacizumab, a nanobody against von Willebrand factor A1 domain, has become crucial. Delayed normalization of ADAMTS13 activity during caplacizumab therapy has been identified. In a retrospective analysis, we compared platelet count, ADAMTS13 activity, its inhibitor, and...

Background: Hereditary thrombotic thrombocytopenic purpura (hTTP), also known as Upshaw-Schulman syndrome, is an ultra-rare, thrombotic microangiopathy resulting from bi-allelic ADAMTS13 mutations and severe congenital ADAMTS13 deficiency. Clinical presentation includes thrombocytopenia, hemolytic anemia and symptoms of organ ischemia (primarily of...

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) results from autoantibody-mediated severe deficiency of ADAMTS13, the Von Willebrand factor (VWF)-cleaving protease. In this context, ultra-large VWF multimers accumulate in the circulation, leading to increased platelet clumping, with subsequent severe thrombocytopenia, microangiopathic he...

Introduction Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare condition that causes fatal ischemic end-organ damage due to autoantibodies against ADAMTS13. iTTP patients treated with caplacizumab in addition to standard treatments show a faster time to platelet recovery and fewer incidences of TTP-related organ damage and death....

Background: Hereditary thrombotic thrombocytopenic purpura (hTTP), or Upshaw-Schulman syndrome, is a rare thrombotic microangiopathy due to a severe congenital deficiency of ADAMTS13 resulting from bi-allelic ADAMTS13 mutations. As in other plasma factor deficiencies, treatment consists of replacement of the missing ADAMTS13, which can currently be...

Transplant-associated thrombotic microangiopathy (TA-TMA) is a fatal complication of hematopoietic stem cell transplantation (HSCT). Since little is known about multimer changes of von Willebrand factor (VWF) in TA-TMA, VWF-degradation product (DP) was analyzed to unravel the mechanism of change in the VWF multimer and disease course. This study en...

In some cases, differentiating thrombotic thrombocytopenic purpura (TTP) from septic disseminated intravascular coagulation (DIC) without measuring ADAMTS13 activity is critical for urgent lifesaving plasma exchange. To investigate whether PLASMIC score without identifying the presence of schistocytes, D-dimer, fibrin/fibrinogen degradation product...

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare medical emergency for which a correct and early diagnosis is essential. As a severe deficiency in A Disintegrin And Metalloproteinase with ThromboSpondin type 1 repeats, member 13 (ADAMTS13) is the underlying pathophysiology, diagnostic strategies require timely monitoring of ADAM...

Thrombotic thrombocytopenic purpura (TTP) can rapidly become a life-threatening condition, and the importance of its appropriate diagnosis and treatment cannot be overstated. Until recently, TTP has mainly been diagnosed by clinical findings such as thrombocytopenia and hemolytic anemia. In addition to these clinical findings, however, reduced acti...

Congenital thrombotic thrombocytopenic purpura (cTTP) is an extremely rare disease characterized by the severe deficiency of a disintegrin and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13), caused by ADAMTS13 mutations. While ADAMTS13 supplementation by fresh frozen plasma (FFP) infusion immediately corrects platelet consumption...

Background: Both immune-mediated thrombotic thrombocytopenic purpura (iTTP) and septic disseminated intravascular coagulation (DIC) are life-threatening disorders developed by platelet-consuming microvascular thrombi and necessitate immediate therapeutic interventions. Although severe deficiencies of plasma haptoglobin in iTTP and factor XIII (FXI...

Background: Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is an ultra-rare autoimmune disorder caused by autoantibodies against ADAMTS13. A strong association of DRB1∗11 with iTTP and DRB1∗11-restricted T-cell epitopes in ADAMTS13 have been reported in Europeans, whereas we previously found DRB1∗08:03 as a susceptible allele in Japane...

Congenital thrombotic thrombocytopenic purpura (cTTP) is caused by a severe deficiency in the plasma metalloprotease ADAMTS-13. The current management of cTTP is dependent on the prophylactic administration of ADAMTS-13 via plasma infusion. This is a demanding therapy for patients because transfusions are lifelong and time-consuming and allergic re...

Introduction Understanding the composition of stroke thrombi retrieved by mechanical thrombectomy is essential to clarify the pathogenesis of stroke. However, it is difficult to evaluate thrombus composition precisely and objectively. Immunohistochemical staining was used to evaluate thrombus composition and age. Materials and methods Consecutive...

Thrombotic thrombocytopenic purpura (TTP) is an ultra-rare and fatal thrombotic disease characterized by systemic ischemic organ damage due to peripheral capillary occlusion by microthrombi. An acquired form of TTP, immune-mediated TTP (iTTP), is caused by the production of auto-antibodies against von Willebrand cleaving protease, also known as ADA...

Although salvage therapy with rituximab is effective in some cases of immune-mediated thrombotic thrombocytopenic purpura (iTTP) refractory to standard plasma exchange (PEX) and glucocorticoid treatment or relapsed after treatment, protocols to address the subsequent high recurrence rate have not been established. We describe the use of cyclosporin...

Background: Patients with essential thrombocythemia (ET) often experience bleeding associated with acquired von Willebrand syndrome (AVWS) when the platelet count is markedly increased. Objective: We investigated whether von Willebrand factor (VWF) degradation is enhanced in patients with ET. Methods: Seventy patients with ET underwent VWF mul...

Neuropsychiatric symptoms comprise one of the five classic symptoms of autoimmune thrombotic thrombocytopenic purpura (aTTP). Although aTTP is typically transient, it is sometimes complicated by cerebral infarction with residual disability. This report presents the case of an 87-year-old man previously admitted to a different hospital with fever an...

Thrombotic thrombocytopenic purpura (TTP) is an extremely rare and fatal thrombotic disorder characterized by impaired enzyme activity of von Willebrand factor cleaving protease, also known as ADAMTS13. Immune-mediated TTP (iTTP) is an acquired form of TTP caused by the production of auto-antibodies against ADAMTS13. The pathophysiology of autoimmu...

Pachychoroid neovasculopathy (PNV) is a new concept of macular disorder. Some cases diagnosed as age-related macular degeneration (AMD) have been re-diagnosed as PNV. However, the biological features of PNV are still uncertain. The purpose of this study was to compare PNV and AMD by analyses focusing on von Willebrand factor (VWF) and complement fa...

Plasma exchange (PEX) using fresh frozen plasma has considerably reduced the mortality rate in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP). However, some patients still do not survive even with treatment, but little information is available regarding which treatment these patients received. This study was conducted to o...

Pachychoroid neovasculopathy (PNV) is a new disease concept. Some cases diagnosed as age-related macular degeneration (AMD) have been re-diagnosed as PNV. However, the biological features of PNV are still uncertain. The purpose of this study was to compare PNV and AMD by an analysis focusing on von Willebrand factor (VWF) and complement factor H (C...

Congenital thrombotic thrombocytopenic purpura (cTTP), known as Upshaw–Schulman syndrome, is an ultrarare thrombotic disorder caused by ADAMTS13 gene mutations; however, its long‐term outcomes have not been widely studied. A questionnaire survey was administered to physicians of patients in the Japanese cTTP registry to characterise these outcomes....

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Fatigue is one of the most common symptoms associated with paroxysmal nocturnal hemoglobinuria (PNH), a rare acquired disorder of hematopoietic stem cells. While it directly impairs lifestyle leading to poor quality of life (QOL), it is not well recognized that fatigue could not depend on the disease activity or percentage of glycosylphosphatidylin...

No abstract available

Immune thrombotic thrombocytopenic purpura (iTTP) is caused by ADAMTS13 deficiency due to anti-ADAMTS13 autoantibodies. Rituximab, an anti-CD20 monoclonal antibody, is often used to suppress these autoantibodies. This retrospective study, conducted in an iTTP cohort in Japan, evaluated the long-term efficacy of rituximab as off-label treatment for...

Background Congenital thrombotic thrombocytopenic purpura (cTTP), otherwise known as Upshaw‐Schulman syndrome,, is an extremely rare hereditary disease. Pregnancy is identified as a trigger for TTP episodes in patients with cTTP. Objectives To investigate the ideal management of pregnant patients with cTTP. Patients/Methods We identified 21 patie...

Introductions Patients with acquired thrombotic thrombocytopenic purpura (TTP) show no severe abnormalities in coagulation or fibrinolysis. However, the exact extent of the abnormalities is unclear. Materials and Methods This study analyzed 138 patients with acquired TTP and 46 patients with septic disseminated intravascular coagulation (DIC) who...

Background Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is an autoimmune disorder caused by neutralizing anti-ADAMTS13 autoantibodies. This condition leads to life-threatening microvascular thrombi in systemic organs due to an imbalance between ADAMTS13 and von Willebrand factor. While several European groups reported that HLA-DRB1*11...

Key Points One third of patients with USS have a neonatal episode of severe hemolytic jaundice with thrombocytopenia induced by an unknown trigger. A USS patient with persisting PDA and recurrent neonatal hemolysis/thrombocytopenia suggests blood flow through the PDA as trigger.

Introduction: von Willebrand factor (VWF) is synthesised in vascular endothelial cells and released into the plasma as unusually large VWF multimers (UL-VWFMs). Sinusoidal endothelial cells are a major target of ischaemia-reperfusion injury due to liver surgery. This study aimed to clarify the effect of hepatectomy on UL-VWFMs. Materials and meth...

Introduction: ADAMTS13 modulates shear-dependent platelet thrombus formation (PTF) by limited proteolysis of von Willebrand factor (VWF). A high-plasma-ratio of VWF antigen to ADAMTS13 activity (VWF:Ag/ADAMTS13:AC) promotes PTF and aggravates shear-induced inflammation mediated by VWF. A role of ADAMTS13 in Kawasaki disease (KD) remains unknown, h...

Background: ADAMTS13 specifically cleaves the peptide bond between Y1605 and M1606 within the VWF-A2 domain. Objective: The VWF contains ABO(H) blood group antigens, which may influence the susceptibility of VWF to ADAMTS13. Methods: Using a unique monoclonal antibody recognizing the Y1605 residue, we have developed a sandwich ELISA to analyze...

Introduction> von Willebrand factor (VWF) is a blood glycoprotein that plays an important role in platelet thrombus formation through interaction with its A1 domain and platelet glycoprotein 1b. Thus, VWF A1 domain was thought to be a good therapeutic target candidate for VWF mediated thrombosis. In this study, we analyzed the inhibitory effects of...

Von Willebrand factor (VWF) is one of the plasma protein carrying ABO(H) blood group antigens, but the combining process of these antigens is not clear. In the present study, we examined whether plasma glycosyltransferase affects the blood group antigens on VWF. VWF expressing H-antigen (H-VWF) from blood group O and bovine serum albumin conjugated...

We investigated the association between von Willebrand factor (VWF) and exudative age-related macular degeneration (AMD) in 114 Japanese patients. Intravitreal injection of vascular endothelial growth factor (VEGF) inhibitor is the most effective therapy for AMD. Therefore, we analyzed changes of VWF antigen (VWF:Ag) and VWF multimers (VWFMs) after...

For pregnant women with essential thrombocythemia (ET), no standard approach for managing the platelet count has been established. We present the cases of two pregnant women with ET treated with interferon (IFN)-alpha. Each case showed a marked platelet decrease, from values within normal limits at the time of delivery, with no severe adverse event...

Key Points Severely decreased ADAMTS13 unbound to VWF may play a key role in the pathogenesis of HELLP syndrome. A qualitative ADAMTS13 assay may be important for diagnosing HELLP syndrome.

Deficient ADAM metalloproteinase with thrombospondin type-1 motif, member 13 (ADAMTS13) activity (ADAMTS13:AC) results in the accumulation of unusually large von Willebrand factor multimers (UL-VWFM) and causes microcirculatory disturbances and multiple organ failure, while endotoxins trigger the activation of a coagulation cascade. The objective o...

Background ADAMTS13 specifically cleaves the peptide bond between Y1605 and M1606 within the von Willebrand factor (VWF)-A2 domain, and down-regulates VWF function, involved in platelet thrombi formation in denuded vascular endothelial cells in vivo. A 250 kD-mature VWF subunit, consisting of 2050 amino acid residues, contains 13 N-linked carbohydr...

Thrombocytopenia, anasarca, fever, reticulin fibrosis, and organomegaly (TAFRO) syndrome is considered as a unique clinicopathologic variant of multicentric Castleman's disease and is recently reported in Japan. This entity represents a severe inflammatory state leading to organ failures such as severe liver dysfunction seen in our case, and can be...

A 47-year-old woman with pancytopenia, excessive systemic lymphadenopathy and splenomegaly was referred to our hospital. The peripheral blood (PB) smear findings indicated neutropenia with lymphoid cells exhibiting hairy projections, while the histological findings of the cervical lymph node (LN) suggested hairy cell leukemia (HCL). In addition, th...