Rituximab therapy for thrombotic thrombocytopenic purpura: a proposed study of the Transfusion Medicine/Hemostasis Clinical Trials Network with a systematic review of rituximab therapy for immune-mediated disorders

Therapeutic modalities in thrombotic thrombocytopenic purpura management among Jehovah's Witness patients: A review of reported cases

INTRODUCTION

Devout members of the Jehovah's Witness faith flatly refuse transfusions of white blood cells, red blood cells, platelets, and plasma. The latter agent is a mainstay in the treatment of thrombotic thrombocytopenic purpura (TTP). Alternative treatment options for Jehovah's Witness patients are needed and reviewed herein.

METHODS

Cases of TTP treatment among Jehovah's Witnesses were obtained from the published literature. Key baseline and clinical data were extracted and summarized.

RESULTS

A total of 13 reports spanning a 23-year period and 15 TTP episodes were identified. Median (IQR) age was 45.5 (29.0-57.5) and 12/13 (93%) patients were female. Neurologic symptoms were present in 7/15 (47%) episodes at presentation. Disease confirmation with ADAMTS13 testing was present in 11/15 (73%) of episodes. Corticosteroids and rituximab were employed in 13/15 (87%) and 12/15 (80%) of cases, respectively, with apheresis-based therapy employed in 9/15 (60%) episodes. For eligible cases, caplacizumab was used in 4/5 (80%) episodes; average time to platelet response was shortest in these cases. Sources of exogenous ADAMTS13 accepted by patients in this series included cryo-poor plasma, FVIII concentrate, and cryoprecipitate.

CONCLUSIONS

Successful management of TTP within the boundaries of the Jehovah's Witness faith is possible.

Recurrent stroke in an African female with idiopathic thrombotic thrombocytopenic purpura: A case report

We report on a young Ghanaian female who was diagnosed with thrombotic thrombocytopenic purpura (TTP) but had an ischemic stroke as the initial presentation. She was successfully treated with therapeutic plasma exchange. This case illustrates how TTP can masquerade as ischemic stroke and the application of PLASMIC score without ADAMTS-13 assay in risk prediction.

Case report of Salmonella derby septicemia complicated with co-occurrence of disseminated intravascular coagulation and thrombotic microangiopathy

BACKGROUND

Both disseminated intravascular coagulation and thrombotic microangiopathy are complications of sepsis as Salmonella septicemia, respectively. They are related and have similar clinical characteristics as thrombopenia and organ dysfunctions. They rarely co-occur in some specific cases, which requires a clear distinction.

CASE PRESENTATION

A 22-year-old woman had just undergone intracranial surgery and suffered from Salmonella derby septicemia with multiorgan involvement in the hospital. Laboratory workup demonstrated coagulation disorder, hemolytic anemia, thrombocytopenia, and acute kidney injury, leading to the co-occurrence of disseminated intravascular coagulation and secondary thrombotic microangiopathy. She received antibiotics, plasma exchange therapy, dialysis, mechanical ventilation, fluids, and vasopressors and gained full recovery without complications.

CONCLUSION

Disseminated intravascular coagulation and secondary thrombotic microangiopathy can co-occur in Salmonella derby septicemia. They should be treated cautiously in diagnosis and differential diagnosis. Thrombotic microangiopathy should not be missed just because of the diagnosis of disseminated intravascular coagulation. Proper and timely identification of thrombotic microangiopathy with a diagnostic algorithm is essential for appropriate treatment and better outcomes.

Molecular Pathogenesis of Endotheliopathy and Endotheliopathic Syndromes, Leading to Inflammation and Microthrombosis, and Various Hemostatic Clinical Phenotypes Based on "Two-Activation Theory of the Endothelium" and "Two-Path Unifying Theory" of Hemostasis

Endotheliopathy, according to the “two-activation theory of the endothelium”, can be triggered by the activated complement system in critical illnesses, such as sepsis and polytrauma, leading to two distinctly different molecular dysfunctions: (1) the activation of the inflammatory pathway due to the release of inflammatory cytokines, such as interleukin 6 and tumor necrosis factor-α, and (2) the activation of the microthrombotic pathway due to the exocytosis of hemostatic factors, such as ultra-large von Willebrand factor (ULVWF) multimers and FVIII. The former promotes inflammation, including inflammatory organ syndrome (e.g., myocarditis and encephalitis) and multisystem inflammatory syndrome (e.g., cytokine storm), and the latter provokes endotheliopathy-associated vascular microthrombotic disease (VMTD), orchestrating thrombotic thrombocytopenic purpura (TTP)-like syndrome in arterial endotheliopathy, and immune thrombocytopenic purpura (ITP)-like syndrome in venous endotheliopathy, as well as multiorgan dysfunction syndrome (MODS). Because the endothelium is widely distributed in the entire vascular system, the phenotype manifestations of endotheliopathy are variable depending on the extent and location of the endothelial injury, the cause of the underlying pathology, as well as the genetic factor of the individual. To date, because the terms of many human diseases have been defined based on pathological changes in the organ and/or physiological dysfunction, endotheliopathy has not been denoted as a disease entity. In addition to inflammation, endotheliopathy is characterized by the increased activity of FVIII, overexpressed ULVWF/VWF antigen, and insufficient ADAMTS13 activity, which activates the ULVWF path of hemostasis, leading to consumptive thrombocytopenia and microthrombosis. Endothelial molecular pathogenesis produces the complex syndromes of inflammation, VMTD, and autoimmunity, provoking various endotheliopathic syndromes. The novel conceptual discovery of in vivo hemostasis has opened the door to the understanding of the pathogeneses of many endotheliopathy-associated human diseases. Reviewed are the hemostatic mechanisms, pathogenesis, and diagnostic criteria of endotheliopathy, and identified are some of the endotheliopathic syndromes that are encountered in clinical medicine.

Coexistence of thrombotic thrombocytopenic purpura and adult-onset Still's disease

The association of Thrombotic thrombocytopenic purpura (TTP) and adult‐onset Still's disease (AOSD) is very uncommon. Hereby, we present a case of TTP occurring in patient with a known AOSD and the successful outcome after plasma exchanges.

Evaluation of Tooth Sensitivity of In-office Bleaching with Different Light Activation Sources: A Systematic Review and a Network Meta-analysis

OBJECTIVES

A systematic review and network meta-analysis were performed to answer the following research question: Are there differences in the risk and the intensity of tooth sensitivity (TS) among eight light activation systems for in-office bleaching in adults?

METHODS

Randomized controlled trials (RCTs) that compared at least two different in-office bleaching light activations were included. The risk of bias (RoB) was evaluated with the RoB tool version 1.0 from the Cochrane Collaboration tool. A random-effects Bayesian mixed treatment comparison (MTC) model was used independently for high- and low-concentration hydrogen peroxide. The certainty of the evidence was evaluated using the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. A comprehensive search was performed in PubMed, Bridge Base Online (BBO), Latin American and Caribbean Health Sciences Literature database (LILACS), Cochrane Library, Scopus, Web of Science, and grey literature without date and language restrictions on April 23, 2017 (updated on September 26, 2019). Dissertations and theses, unpublished and ongoing trials registries, and IADR (International Association for Dental Research) abstracts (2001-2019) were also searched.

RESULTS

After title and abstract screening and the removal of duplicates, 32 studies remained. Six were considered to be at low RoB, three had high RoB, and the remaining had an unclear RoB. The MTC analysis showed no significant differences among the treatments in each network. In general, the certainty of the evidence was graded as low due to unclear RoB and imprecision.

CONCLUSION

There is no evidence that the risk and intensity of TS are affected by light activation during in-office bleaching.

[Treatment of thrombotic thrombocytopenic purpura]

The review discusses approaches to treatment of acquired thrombotic thrombocytopenic purpuгa (aTTP). In patients with aTTP plasma exchanges, glucocorticosteroids allow to stop an acute attack of TTP, and use of rituximab allows to achieve remission. In recent years, caplacizumab has been used. Treatment options such as cyclosporin A, bortezomib, splenectomy, N-acetylcysteine, recombinant ADAMTS13 are also described. Separately discussed issues of management of patients with TTP during pregnancy, and pediatric patients with TTP.

Thrombotic Thrombocytopenic Purpura: When Basic Science Meets Clinical Research

The therapeutic landscape of thrombotic thrombocytopenic purpura (TTP) is rapidly changing with the recent availability of new targeted therapies. This progressive shift from empiricism to pathophysiology-based treatments reflects an intensive interaction between the continuous findings in the field of basic science and an efficient collaborative clinical research and represents a convincing example of the strength of translational medicine. Despite the rarity of TTP, national and international efforts could circumvent this limitation and shed light on the epidemiology, clinical presentation, prognosis, and long-term outcome of this disease. Importantly, they also provided high-quality results and practice changing studies for the benefit of patients. We report here the most recent therapeutic findings that allowed progressively improving the prognostic of TTP, both at the acute phase and through long-term outcome.

When targeted therapies alleviate the burden of TPE: The example of immune-mediated TTP

Thrombotic thrombocytopenic purpura is a rare and severe disease that manifests as a thrombotic microangiopathy with severe thrombocytopenia and variable multiorgan failure. The disease relies on a severe deficiency in a disintegrin and metalloprotease with thrombospondin type-1 repeats, 13^th member (ADAMTS13), the von Willebrand factor (vWF) cleaving protease which can be either inherited (congenital TTP) or immune-mediated (iTTP). In iTTP, the therapeutic strategy has long relied on therapeutic plasma exchange alone which still represents the only way to deliver large amounts of ADAMTS13 without risking fluid overload. Yet, several therapeutic strategies have been developed in recent years and are about to transform the standard of care of iTTP. The immunosuppressive regimen now increasingly encompasses the administration of frontline rituximab to all patients. Moreover, the impressive results of the anti-vWF nanobody caplacizumab in phase 2 and 3 studies have recently prompted its approval by health authorities for the initial treatment of the disease. The increasing use of these highly effective targeted therapies should translate in a reduced need for therapeutic plasma exchange and an improvement in the prognosis of the disease. Nevertheless, and until the development of a recombinant ADAMTS13, this cornerstone therapy remains irreplaceable.

Differences and similarities between disseminated intravascular coagulation and thrombotic microangiopathy

Introduction

Both disseminated intravascular coagulation (DIC) and thrombotic microangiopathy (TMA) cause microvascular thrombosis associated with thrombocytopenia, bleeding tendency and organ failure.

Reports and discussion

The frequency of DIC is higher than that of thrombotic thrombocytopenic purpura (TTP). Many patients with TMA are diagnosed with DIC, but only about 15% of DIC patients are diagnosed with TMA. Hyperfibrinolysis is observed in most patients with DIC, and microangiopathic hemolytic anemia is observed in most patients with TMA. Markedly decreased ADAMTS13 activity, the presence of Shiga-toxin-producing Escherichia coli (STEC) and abnormality of the complement system are useful for the diagnosis of TTP, STEC-hemolytic uremic syndrome (HUS)and atypical HUS, respectively. However, there are no specific biomarkers for the diagnosis of DIC.

Conclusion

Although DIC and TMA are similar appearances, all coagulation, fibrinolysis and platelet systems are activated in DIC, and only platelets are markedly activated in TMA.

Therapeutic Apheresis in Hematologic, Autoimmune and Dermatologic Diseases With Immunologic Origin

The process of curing a patient by removing his illness by extracting blood is a very old one. Many years ago, phlebotomy was practiced to cure illness. Now, this old process, placed on a rational basis with therapeutic apheresis (TA), is being followed in clinical practice. Therapeutic plasma exchange (TPE) with hollow fiber modules has been used in different severe diseases for more than 40 years. Based on many years of experience with the extracorporeal circulation in end-stage renal disease, the authors herein give an overview of TA in immunological diseases, especially in hematologic, autoimmune and dermatologic diseases. Updated information on immunology and molecular biology of different immunological diseases is discussed in relation to the rationale for apheresis therapy and its place in combination with other modern therapies. With the introduction of novel and effective biologic agents, TA is indicated only in severe cases, such as in rapid progression despite immunosuppressive therapy and/or biologic agents. In mild forms of autoimmune disease, treatment with immunosuppressive therapies and/or biologic agents seems to be sufficient. The prognosis of autoimmune diseases with varying organ manifestations has improved in recent years, due in part to very aggressive therapy schemes. For the immunological diseases that can be treated with TA, the guidelines of the German Working Group of Clinical Nephrology and of the Apheresis Applications Committee of the American Society for Apheresis are cited. TA has been shown to effectively remove the autoantibodies from blood and lead to rapid clinical improvement.

Evaluation and Management of Patients With Thrombotic Thrombocytopenic Purpura

Thrombotic thrombocytopenic purpura (TTP) describes syndromes with multiple etiologies, some of which are rapidly fatal without plasma exchange treatment. Although there have been advances in understanding the pathogenesis of TTP, evaluation and management remain difficult because there are no specific diagnostic criteria, as TTP can be clinically similar to other acute disorders, such as sepsis, disseminated malignancy, malignant hypertension, and preeclampsia, and because urgent treatment is required. An unexpected observation of anemia and thrombocytopenia should trigger consideration of TTP; evidence that the anemia is due to microangiopathic hemolysis, suggested by the presence of red cell fragmentation on the blood smear, supports the diagnosis. When the diagnostic criteria of microangiopathic hemolytic anemia and thrombocytopenia without an apparent alternative etiology are fulfilled, plasma exchange treatment is appropriate. However, plasma exchange has risks for severe complications and death; therefore, this management decision must be balanced against the confidence in the diagnosis. With plasma exchange treatment, approximately 80% of patients survive, in contrast to only 10% in the era prior to the availability of plasma exchange. The continuing mortality from TTP, the risks of plasma exchange treatment, and the potential for recurrent episodes of TTP are clinical challenges that remain to be solved.

Population pharmacokinetics of rituximab with or without plasmapheresis in kidney patients with antibody-mediated disease

AIMS

Both rituximab and plasmapheresis can be associated in the treatment of immune-mediated kidney diseases. The real impact of plasmapheresis on rituximab pharmacokinetics is unknown. The aim of this study was to compare rituximab pharmacokinetics between patients requiring plasmapheresis and others without plasmapheresis.

METHODS

The study included 20 patients receiving one or several infusions of rituximab. In 10 patients, plasmapheresis sessions were also performed (between two and six sessions per patient). Rituximab concentrations were measured in blood samples in all patients and in discarded plasma obtained by plasmapheresis using an enzyme-linked immunosorbent assay method. Data were analysed according to a population pharmacokinetic approach.

RESULTS

The mean percentage of rituximab removed during the first plasmapheresis session ranged between 47 and 54% when plasmapheresis was performed between 24 and 72 h after rituximab infusion. Rituximab pharmacokinetics was adequately described by a two-compartment model with first-order elimination. Plasmapheresis had a significant impact on rituximab pharmacokinetics, with an increase of rituximab clearance by a factor of 261 (95% confidence interval 146-376), i.e. from 6.64 to 1733 ml h(-1) . Plasmapheresis performed 24 h after rituximab infusion decreased the rituximab area under the curve by 26%.

CONCLUSIONS

Plasmapheresis removed an important amount of rituximab when performed less than 3 days after infusion. The removal of rituximab led to a significant decrease of the area under the curve. This pharmacokinetic observation should be taken into account for rituximab dosing, e.g. an additional third rituximab infusion may be recommended when three plasmapheresis sessions are performed after the first rituximab infusion.

The Oklahoma Thrombotic Thrombocytopenic Purpura-haemolytic Uraemic Syndrome Registry. A model for clinical research, education and patient care

The Oklahoma Thrombotic Thrombocytopenic Purpura-Haemolytic Uraemic Syndrome (TTP-HUS) Registry has a 24 year record of success for collaborative clinical research, education, and patient care. This article tells the story of how the Registry began and it describes the Registry's structure and function. The Registry provides a model for using a cohort of consecutive patients to investigate a rare disorder. Collaboration between Oklahoma, United States and Bern, Switzerland has been the basis for successful interpretation of Registry data. Registry data have provided new insights into the evaluation and management of TTP. Because recovery from acute episodes of TTP has been assumed to be complete, the increased prevalence of hypertension, diabetes, depression, and death documented by long-term follow-up was unexpected. Registry data have provided opportunities for projects for students and trainees, education of physicians and nurses, and also for patients themselves. During our follow-up, patients have also educated Registry investigators about problems that persist after recovery from an acute episode of TTP. Most important, Registry data have resulted in important improvements for patient care.

Thrombotic microangiopathy: current knowledge and outcomes with plasma exchange

The classification of thrombotic microangiopathy has evolved and expanded due to treatment and mechanistic advances. The two basic clinical forms of thrombotic microangiopathy (excluding disseminated intravascular coagulation [DIC]), thrombotic thrombocytopenic purpura (TTP), and hemolytic uremic syndrome (HUS) encompass a wide range of primary and secondary forms. The advent of plasma therapy and the identification of an inhibitor to ADAMTS13 in the idiopathic or acute forms of TTP and its absence in diarrheal HUS have had a major impact on our current classification of thrombotic microangiopathy. In adults, the difficulty of differentiating TTP, which is much more common than HUS and the need for a speedy diagnosis to provide life-saving plasma therapy has resulted in the term TTP/HUS for adult forms of thrombotic microangiopathy that present with unexplained thrombocytopenia and microangiopathic hemolytic anemia without a DIC. In this adult population a primary idiopathic and hereditary form as well as eight known secondary categories or clinical forms of TTP/HUS have been identified. HUS also embraces a primary (atypical HUS) and secondary forms (majority, diarrheal HUS secondary to Escherichia coli 0157:H7). In children, who present with HUS with no preceding history of diarrhea, plasma therapy is also offered on an urgent basis and studies are carried out to determine if they are suffering an abnormality in complement activation that may require eculizumab therapy. The advent of plasma therapy in the treatment of thrombotic microangiopathy has led to a clearer understanding of the role of ADAMTS13, both short- and long-term outcomes and the need for future surveillance and intervention.

Attending rounds: microangiopathic hemolytic anemia with renal insufficiency

The classification of thrombotic microangiopathy has evolved and expanded due to treatment and advances in understanding of the diseases associated with this clinical presentation. The three clinical forms of thrombotic microangiopathy-thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), and disseminated intravascular coagulation-encompass a wide range of disorders that can be classified as either primary (idiopathic) or secondary to another identifiable disease or clinical context. Identification of an inhibitor to a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) in the idiopathic and acute forms of TTP, recognition of the absence of ADAMTS13 inhibition in diarrheal HUS, identification of complement abnormalities in atypical HUS, and a better understanding of the role of plasma therapy, rituximab, and eculizumab therapy have all had a major effect on current understanding of the thrombotic microangiopathies. In this Attending Rounds, a patient with a thrombotic microangiopathy is presented, along with discussion highlighting the difficulty of differentiating TTP from HUS and disseminated intravascular coagulation, the need for a prompt diagnosis, and the role for plasma therapy in appropriately selected patients. The discussion attempts to provide a simple clinical approach to the diagnosis, treatment options, and future course of adults and children suffering from a thrombotic microangiopathy.

[Thrombophilic states in intensive care medicine]

Thrombophilic states are common in intensive care medicine. Generally, they are complications of serious underlying diseases or adverse effects of treatment measures. The attributive mortality rate for thrombophilic states is high. Early recognition and management are, thus, indispensable. In this review, important diagnostic and therapeutic aspects are briefly summarized. Leading symptoms and the context to the underlying disease or therapy, which result in a thrombophilic state, are the basics for a specific diagnostic workup. Almost all current treatment recommendations are based on expert opinion.

Anti-CD20 monoclonal antibodies and their use in adult autoimmune hematological disorders

Autoimmune hematological disorders encompass a broad group of hematological conditions characterized by the loss of self-tolerance to a variety of antigens. Despite good response to first-line therapy in the majority of patients, relapses are common, necessitating new and safe therapeutic options. The anti-CD20 monoclonal antibody rituximab has led to substantial improvement in the treatment of malignant and immune-mediated disorders involving B cells. Although experience with rituximab in immune-mediated hematological disorders is rarely supported by randomized trials, there is now substantial experience with rituximab suggesting that anti-CD20 therapy is an effective and well-tolerated alternative to immunosuppressive therapy in these disorders. However, caution is needed based on recent reports describing-sometimes severe-rituximab-related complications.

[Thrombotic-thrombocytopenic purpura]

Thrombotic-thrombocytopenic purpura (TTP) is a microangiopathic disorder characterized by multiple von Willebrand-Factor (vWF) rich microthrombi affecting the arterioles and capillary vessels of several organs. Ultra large von Willebrand multimers cause the blood clotting process by linking to platelets due to a lack of a plasma metalloprotease named ADAMTS13. Deficiency of this vWF-cleaving enzyme is caused by an inborn mutation in the gene coding or, more often, by acquired autoantibodies that inhibit ADAMTS13. TTP is a life-threatening disease which requires urgent admission to a hematological centre. Plasmapheresis therapy should be started immediately when diagnosis of primary TTP is likely. Patients typically present with schistozytes, hemolysis, thrombocytopenia and neurological abnormalities such as headache, focal deficits or coma. The monoclonal CD20 antibody rituximab targets ADAMTS13 antibody production and has the potential to be an effective therapy for relapsed TTP or initial treatment to shorten duration of plasma exchange.

Thrombotic microangiopathy in haematopoietic cell transplantation: an update

Allogeneic hematopoietic cell transplantation (HCT) represents a vital procedure for patients with various hematologic conditions. Despite advances in the field, HCT carries significant morbidity and mortality. A rare but potentially devastating complication is transplantation-associated thrombotic microangiopathy (TA-TMA). In contrast to idiopathic TTP, whose etiology is attributed to deficient activity of ADAMTS13, (a member of the A Disintegrin And Metalloprotease with Thrombospondin 1 repeats family of metalloproteases), patients with TA-TMA have > 5% ADAMTS13 activity. Pathophysiologic mechanisms associated with TA-TMA, include loss of endothelial cell integrity induced by intensive conditioning regimens, immunosuppressive therapy, irradiation, infections and graft-versus-host (GVHD) disease. The reported incidence of TA-TMA ranges from 0.5% to 75%, reflecting the difficulty of accurate diagnosis in these patients. Two different groups have proposed consensus definitions for TA-TMA, yet they fail to distinguish the primary syndrome from secondary causes such as infections or medication exposure. Despite treatment, mortality rate in TA-TMA ranges between 60% to 90%. The treatment strategies for TA-TMA remain challenging. Calcineurin inhibitors should be discontinued and replaced with alternative immunosuppressive agents. Daclizumab, a humanized monoclonal anti-CD25 antibody, has shown promising results in the treatment of TA-TMA. Rituximab or the addition of defibrotide, have been reported to induce remission in this patient population. In general, plasma exchange is not recommended.

Long-term follow-up of idiopathic thrombotic thrombocytopenic purpura treated with rituximab

Rituximab may be used to treat patients with thrombotic thrombocytopenic purpura (TTP) refractory to plasma exchange or recurrent disease. While initial response rates are reported to be high, long-term follow-up data of patients treated with rituximab are not available to date, however important to estimate the safety and benefit of this treatment. Twelve patients with non-familial idiopathic TTP refractory to plasma exchange or with recurrent disease treated with rituximab between 2000 and 2008 were reexamined. The median follow-up was 49.6 months, ranging from 11 to 97 months. All patients achieved initial complete remission after application of rituximab. During follow-up, nine patients remained disease-free and three patients suffered from recurrent disease. All patients with recurrent disease responded to subsequent rituximab therapy. No long-term side effects were noted during the follow-up period. In conclusion, rituximab represents an effective second-line treatment option in relapsing or refractory TTP. Still, patients need to be closely monitored for relapses with extended follow-up.

Survival and relapse in patients with thrombotic thrombocytopenic purpura

Survival of patients with thrombotic thrombocytopenic purpura (TTP) improved dramatically with plasma exchange treatment, revealing risk for relapse. The Oklahoma TTP Registry is a population-based inception cohort of all 376 consecutive patients with an initial episode of clinically diagnosed TTP (defined as microangiopathic hemolytic anemia and thrombocytopenia with or without signs and symptoms of ischemic organ dysfunctions) for whom plasma exchange was requested, 1989 to 2008. Survival was not different between the first and second 10-year periods for all patients (68% and 69%, P = .83) and for patients with idiopathic TTP (83% and 77%, P = .33). ADAMTS13 activity was measured in 261 (93%) of 282 patients since 1995. Survival was not different between patients with ADAMTS13 activity < 10% (47 of 60, 78%) and patients with 10% or more (136 of 201, 68%, P = .11). Among patients with ADAMTS13 activity < 10%, an inhibitor titer of 2 or more Bethesda units/mL was associated with lower survival (P = .05). Relapse rate was greater among survivors with ADAMTS13 activity < 10% (16 of 47, 34%; estimated risk for relapse at 7.5 years, 41%) than among survivors with ADAMTS13 activity of 10% or more (5 of 136, 4%; P < .001). In 41 (93%) of 44 survivors, ADAMTS13 deficiency during remission was not clearly related to subsequent relapse.

Rituximab was effective on refractory thrombotic thrombocytopenic purpura but induced a flare of hemophagocytic syndrome in a patient with systemic lupus erythematosus

We report the case of a patient with systemic lupus erythematosus (SLE) who first revealed hemophagocytic syndrome (HPS), which was treated successfully with glucocorticoid and intravenous cyclophosphamide. The patient then demonstrated refractory thrombotic thrombocytopenic purpura (TTP) with normal a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-13 activity that responded well to rituximab. After rituximab treatment, the patient showed a flare of HPS that was controlled by additional intravenous cyclophosphamide treatment. This case showed that TTP with normal ADAMTS-13 activity is B-cell dependent and indicated that B-cell depletion might exacerbate some autoimmune conditions in SLE.

New treatments for idiopathic thrombocytopenic purpura: rethinking old hypotheses

BACKGROUND

The efficacy of thrombopoietin (TPO) mimetics in patients with idiopathic thrombocytopenic purpura (ITP) reaffirms that impaired platelet production is an important mechanism. New strategies to reduce platelet destruction, like rituximab, are also effective.

OBJECTIVES

To describe the efficacy and safety of rituximab and the TPO mimetics, romiplostim and eltrombopag, and how they relate to ITP pathogenesis.

METHODS

Narrative review summarizing full publications and meeting abstracts.

RESULTS/CONCLUSIONS

A 4-week course of rituximab is associated with a platelet count response in 60% of patients with ITP, and durable responses have been observed. Subtle increases in infection have been reported. Romiplostim and eltrombopag are each associated with a 60 - 85% response while on treatment. Transient bone marrow reticulin with romiplostim and elevated liver enzymes with eltrombopag are rare side effects. The application of these agents in non-splenectomized patients requires further study.

Rituximab therapy in two children with autoimmune thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare disease among pediatric patients, in whom it may be mistaken for hemolytic uremic syndrome (HUS) and idiopathic thrombocytopenic purpura (ITP). Familial forms are caused by mutations in the ADAMTS13 gene, whereas acquired forms may result from an inhibitory antibody directed against ADAMTS13, a metalloprotease that cleaves very large multimers of Von Willebrand factor (VWF), thereby preventing platelet aggregation in blood vessels. We report two cases of TTP. The first was a 15-year-old girl with her first episode of TTP that failed to respond after 10 days of plasmapheresis and was treated with rituximab; she has remained in remission at 12 months of follow-up. The second was a 6-year-old boy with acquired relapsing TTP previously managed with plasmapheresis and prednisolone, who presented with a third relapse that was treated with plasmapheresis and rituximab; he remains in remission 17 months after treatment. Rituximab has been used by pediatricians for treating B cell malignancy, autoimmune diseases and antibody-mediated diseases, such as the Factor VIII inhibitors in hemophilia A, and may also have a promising role in children with acute refractory or chronic relapsing TTP.

Sustained response with rituximab in patients with thrombotic thrombocytopenic purpura: a report of 13 cases and review of the literature

Idiopathic thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease mediated by autoantibodies directed against ADAMTS-13. A number of small series and case reports have shown promising results with rituximab in refractory or relapsed TTP. In this report, we present 13 patients with TTP treated with rituximab. Twelve of the 13 patients (92%) achieved complete response; no subsequent relapses occurred with median follow-up of 24 months (range, 13-84 months). The addition of rituximab to standard therapy appears to be effective in sustaining long-term remission in TTP. However, the optimal dosing and timing of rituximab warrant further investigation. Am. J. Hematol., 2009. (c) 2009 Wiley-Liss, Inc.

Thrombotic thrombocytopenic purpura and adult onset Still's disease

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) has a high mortality rate if undiagnosed and untreated. Although recent literature supports the role of ADAMTS13 (a disintegrin-like metalloproteinase with thrombospondin type 1 repeats), the von Willebrand factor cleaving protease, in the pathogenesis of the disease, many aspects of the disease remain a mystery. Various drugs and autoimmune conditions, such as systemic lupus erythematosus and the antiphospholipid syndrome, have been observed in association with TTP. Adult onset Still's disease (AOSD) has been reported less frequently in association with TTP.

PRESENTATION

We report the case of a 43-year-old African American man who initially presented with fever and joint pain and was later diagnosed with TTP. He responded initially to plasma exchange, but never achieved complete remission. He eventually required splenectomy for complete resolution of symptoms of TTP, but the arthritis never resolved, resulting in several admissions for joint pain. The arthritis was eventually diagnosed as AOSD.

DISCUSSION

Literature review shows that the autoimmune diseases usually associated with TTP include systemic lupus erythematosus and the antiphospholipid syndrome. Eight reports of AOSD with TTP have been reported, but our case is unique in several aspects. Previous case reports have described TTP occurring in patients with known AOSD; here, we describe TTP preceding or coinciding with the onset of AOSD. Interestingly, the patient's AOSD-associated arthritis responded to plasma exchange, but did not resolve after splenectomy. The coincident onset of AOSD and TTP in this patient lead us to suspect a common pathophysiologic pathway in the pathogenesis for both of these diseases.

Thrombotic microangiopathy in haematopoietic stem cell transplantation: diagnosis and treatment

Each year in the US, more than 10 000 patients benefit from allogeneic haematopoietic stem cell transplantation (HSCT), a modality that offers an excellent chance of eradicating malignancy but confers a higher risk of treatment-related mortality. An uncommon but devastating consequence of HSCT is transplantation-associated thrombotic microangiopathy (TA-TMA). The incidence of TA-TMA ranges from 0.5% to 76%, with a mortality rate of 60-90% despite treatment. Although there appears to be a consistent treatment approach to idiopathic thrombotic thrombocytopenic purpura (TTP) using plasma exchange, corticosteroids and rituximab, the treatment strategies for TA-TMA are perplexing, in part, because the literature regarding this complex condition does not provide true consensus for incidence, aetiology, diagnostic criteria, classification and optimal therapy. The classic definition of idiopathic TTP includes schistocytes on the peripheral blood smear, thrombocytopenia and increased serum lactate dehydrogenase. Classic idiopathic TTP has been attributed to deficient activity of the metalloproteinase responsible for cleaving ultra-large von Willebrand factor multimers. This protease is a member of the 'a disintegrin and metalloprotease with thrombospondin type 1 motif' family and is subsequently named ADAMTS-13. Severely deficient ADAMTS-13 activity (<5% of normal) is associated with idiopathic TTP in 33-100% of patients. In constrast to the pathophysiology of idiopathic TTP, patients with TA-TMA have >5% ADAMTS-13 serum activity. These data may explain why plasma exchange, a standard treatment modality for idiopathic TTP that restores ADAMTS-13 activity, is not effective in TA-TMA. TA-TMA has a multifactorial aetiology of endothelial damage induced by intensive conditioning therapy, irradiation, immunosuppressants, infection and graft-versus-host disease. Treatment consists of substituting calcineurin inhibitors with an alternative immunosuppressive agent that possesses another mode of action. One candidate may be daclizumab, especially in those with mild to moderate TMA. Rituximab therapy or the addition of defibrotide may also be beneficial. In general, plasma exchange is not recommended.

The thrombotic thrombocytopenic purpura and hemolytic uremic syndromes: evaluation, management, and long-term outcomes experience of the Oklahoma TTP-HUS Registry, 1989-2007

The Oklahoma thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) Registry, an inception cohort of 382 consecutive patients with TTP-HUS, provides a complete community perspective of these syndromes. TTP, as defined by thrombocytopenia and microangiopathic hemolytic anemia without an alternative etiology, is the appropriate term for all adults. These limited diagnostic criteria are supported by the presenting features of patients with ADAMTS13 deficiency, in whom both neurologic and renal abnormalities are uncommon. HUS is the appropriate term for children who fulfill these diagnostic criteria and who also have renal failure. These definitions are consistent with current management: plasma exchange is the essential treatment for most adults; supportive care is sufficient for children with HUS. Plasma exchange treatment has decreased the mortality of TTP from 90 to 10%. Patients with acquired autoimmune ADAMTS13 deficiency may also require immunosuppressive treatment to achieve a durable remission. Recovery has revealed previously unrecognized long-term risks. Recurrent acute episodes occur in approximately 40% of patients with acquired ADAMTS13 deficiency; most relapses occur within the first year and most patients have only one relapse. Adults with TTP of any etiology have a high risk for persistent minor cognitive abnormalities.

Mechanisms of microvascular thrombosis in thrombotic thrombocytopenic purpura

Recent studies have demonstrated that thrombotic thrombocytopenic purpura (TTP), a serious thrombotic disorder affecting the arterioles and capillaries of multiple organs, is caused by a profound deficiency in the von Willebrand factor cleaving metalloprotease, ADAMTS13. ADAMTS13, a 190-kD plasma protease originating primarily in hepatic stellate cells, prevents microvascular thrombosis by cleaving von Willebrand factor when the substrate is conformationally unfolded by high levels of shear stress in the circulation. Deficiency of ADAMTS13, due to genetic mutations or inhibitory autoantibodies, leads to accumulation of superactive forms of vWF, resulting in vWF-platelet aggregation and microvascular thrombosis. Analysis of ADAMTS13 has led to the recognition of subclinical TTP and atypical TTP presenting with thrombocytopenia or acute focal neurological deficits without concurrent microangiopathic hemolysis. Infusion of plasma replenishes the missing ADAMTS13 and ameliorates the complications of hereditary TTP. The patients are at risk of both acute and chronic renal failure if they receive inadequate plasma therapy. The more frequent, autoimmune type of TTP requires plasma exchange therapy and perhaps immunomodulatory measures. Current studies focus on the factors affecting the phenotypic severity of TTP and newer approaches to improving the therapies for the patients.

A comparison of thrombotic thrombocytopenic purpura in an inception cohort of patients with and without systemic lupus erythematosus

OBJECTIVES

To compare the clinical presentation, response to therapy and outcome of thrombotic thrombocytopenic purpura (TTP) in an inception cohort of patients with and without SLE.

METHODS

Medical records of patients diagnosed with TTP at Singapore General Hospital between January 2003 and December 2007 were reviewed.

RESULTS

Ten idiopathic TTP (iTTP) and eight SLE-associated TTP (sTTP) patients were identified, with iTTP patients being older (mean 50.4 vs 34.5 yrs). Five iTTP patients were ANA positive but did not have any features of SLE. All sTTP patients had active SLE at TTP diagnosis and had more renal involvement than iTTP (87.5% vs 50%). The mean duration from the first symptom suggestive of TTP to diagnosis was 7.7 days and 19.5 days in iTTP and sTTP patients. All patients received high-dose corticosteroids. Cytotoxic and immunosuppressive drugs were used more commonly (87.5% vs 50%) and earlier (Day 2/3 vs after Day 7) in sTTP patients. Vincristine was the drug of choice in iTTP and cyclophosphamide in sTTP. Three SLE patients received rituximab. Mortality for iTTP and sTTP was 50% (95% CI 19%, 81%) and 62.5% (95% CI 29%, 96%), respectively. The mean (s.d.) time to complete remission was 31.3 (+/- 26.4) days in sTTP (n = 3) and 16.8 (+/- 6.1) days in iTTP (n = 5).

CONCLUSION

Despite early and more aggressive therapy in sTTP, mortality was higher and the time to complete remission were longer, suggesting that sTTP is more severe. The tempo of development of TTP in SLE patients was slower.

Rituximab as an adjunct to plasma exchange in TTP: a report of 12 cases and review of literature

Idiopathic thrombotic thrombocytopenic purpura (TTP) is caused by the production of autoantibodies against the Von Willebrand factor cleaving enzyme. This provides a rationale for the use of rituximab in this disease. We report a retrospective review of 12 patients treated with rituximab for TTP refractory to plasma exchange. Eleven patients were treated during initial presentation, and one patient was treated for recurrent relapse. Ten patients responded to treatment. Median time to response after first dose of rituximab was 10 days (5-32). Of the 11 patients treated during initial presentation, nine remain free of relapse after a median follow-up of 57+ months (1+-79+). Two patients died during initial treatment. One patient was lost to follow-up 1 month after achieving complete response. The patient treated for recurrent disease during second relapse remained disease free for 2years, relapsed and was treated again with rituximab, and was in remission for 22 months. She relapsed again, was retreated, and has now been in remission for 21+ months. We conclude that rituximab is an useful addition to plasma exchange treatment in TTP, but its exact role and dosing need to be verified in prospective studies.

Interventions for haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura

BACKGROUND

Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are related conditions with similar clinical features of variable severity. Survival of patients with HUS and TTP has improved greatly over the past two decades with improved supportive care for patients with HUS and by the use of plasma exchange (PE) with fresh frozen plasma (FFP) for patients with TTP. Separate pathogenesis of these two disorders has become more evident, but management overlaps.

OBJECTIVES

To evaluate the benefits and harms of different interventions for HUS and TTP separately, in patients of all ages.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), conference proceedings, reference lists of articles and text books and contact with investigators were used to identify relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating any interventions for HUS or TTP in patients of all ages.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and evaluated study reporting quality using standard Cochrane criteria. Analysis was undertaken using a random effects model and results expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

For TTP, we found six RCTs (331 participants) evaluating PE with FFP as the control. Interventions tested included antiplatelet therapy (APT) plus PE with FFP, FFP transfusion and PE with cryosupernatant plasma (CSP). Two studies compared plasma infusion (PI) to PE with FFP and showed a significant increase in failure of remission at two weeks (RR 1.48, 95% 1.12 to 1.96) and all-cause mortality (RR 1.91, 95% 1.09 to 3.33) in the PI group. Seven RCTs were undertaken in children with HUS. None of the assessed interventions used (FFP transfusion, heparin with or without urokinase or dipyridamole, shiga toxin binding protein and steroids) were superior to supportive therapy alone, for all-cause mortality, neurological/extrarenal events, renal biopsy changes, proteinuria or hypertension at the last follow-up visit. Bleeding was significantly higher in those receiving anticoagulation therapy compared to supportive therapy alone (RR 25.89, 95% CI 3.67 to 182.83).

AUTHORS' CONCLUSIONS

PE with FFP is still the most effective treatment available for TTP. For patients with HUS, supportive therapy including dialysis is still the most effective treatment. All studies in HUS have been conducted in the diarrhoeal form of the disease. There were no RCTs evaluating the effectiveness of any interventions on patients with atypical HUS who have a more chronic and relapsing course.

Thrombotic thrombocytopenic purpura related to severe ADAMTS13 deficiency in children

Thrombotic thrombocytopenic purpura (TTP) related to a severely deficient activity of the von Willebrand factor cleaving protease, ADAMTS (A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats) 13, is a life-threatening event, the onset of which may occur as early as childhood. TTP is either inherited (Upshaw-Schulman syndrome) via ADAMTS13 gene mutations (neonatal onset) or acquired via anti-ADAMTS13 autoantibodies (childhood onset). TTP is due to platelet- and von-Willebrand-factor-rich thrombi of the microvasculature, inducing mechanical hemolytic anemia, consumption thrombocytopenia, and multivisceral ischemia. Clinical course consists of relapsing acute events triggered mostly by infections, associated icterus and hyperbilirubinemia, severe hemolytic anemia with schistocytosis and a negative Coombs test, severe thrombocytopenia, and sometimes symptoms related to visceral ischemia (renal failure, central nervous system vascular events, other organ failure). The recently available ADAMTS13 laboratory investigation combining measurement of ADAMTS13 activity in plasma, search for an ADAMTS13 circulating inhibitor, and anti-ADAMTS13 IgG and ADAMTS13 gene sequencing is a crucial addition to TTP diagnosis. Plasma exchanges are first-line treatment of acquired TTP, combined with steroids and immunosuppressive drugs. Curative treatment of acute events in Upshaw-Schulman syndrome relies on plasma infusions (provider of active ADAMTS13). Guidelines for preventive treatment of relapses are not clearly established but should associate plasmatherapy and caution to triggers of relapses. Therapeutic perspectives are focused on the development of concentrated plasma-derived ADAMTS13 or recombinant ADAMTS13.

Lessons learned from the Oklahoma thrombotic thrombocytopenic purpura-hemolytic uremic syndrome registry

The Oklahoma TTP-HUS Registry provides a complete community perspective of thrombotic thrombocytopenic purpura (TTP). This is possible because plasma exchange is the essential treatment for TTP and the Oklahoma Blood Institute provides all plasma exchange procedures for a region encompassing most of the State, including 58 of Oklahoma's 77 counties. The Registry is an inception cohort of consecutive patients for whom plasma exchange treatment was requested for a diagnosis of either TTP or hemolytic uremic syndrome (HUS). All 382 patients identified from January 1, 1989 to December 31, 2007 have consented to be enrolled. Complete follow-up is available for 380 of 382 patients. Patients are described both by clinical categories, related to their associated conditions and clinically apparent etiologies, and by the presence of severe ADAMTS13 deficiency. ADAMTS13 activity has been measured on 235 (93%) of 254 patients since 1995. Registry data have provided new perspectives on the definition and diagnoses of these syndromes as well as their outcomes. Long-term follow-up has documented that relapse is common among patients with ADAMTS13 deficiency but rarely occurs in patients without ADAMTS13 deficiency. Long-term follow-up has also documented persistent abnormalities of health-related quality-of-life and cognitive function. In addition to providing new perspectives on the natural history of these syndromes, The Oklahoma TTP-HUS Registry provides a support group for our patients, information about evaluation and management for community physicians, and a resource for research and educational programs.

New treatment options for immune-mediated hematological disorders

In recent years, there has been a tremendous increase in the number of clinical studies with monoclonal antibodies and small molecules in the treatment of hematological malignancies. Clinical observations have shown that some of these molecules may also aid in the treatment of immune-mediated hematological disorders. Moreover, immunotherapy has become an important treatment cornerstone in other, non-hematological, auto-immune diseases. This paper reviews the current state of the use of these new molecules in the treatment of the most frequently encountered immune-mediated hematological disorders: auto-immune hemolytic anemia (AIHA), idiopathic thrombocytopenic purpura (ITP), and thrombotic thrombocytopenic purpura (TTP).