Splenectomy done during hematologic remission to prevent relapse in patients with thrombotic thrombocytopenic purpura

Thrombotic Thrombocytopenia Masquerading As COVID-19 Infection

Thrombotic thrombocytopenic purpura (TTP) is a rare and challenging diagnosis that consists of thrombotic microangiopathy due to complete or severe deficiency of ADAMTS13 protease that can present at any age. It is very important to have a suspicion concerning this disease as mortality can be very high if it goes unnoticed. This case describes a patient that presented with gastrointestinal symptoms and hematuria and was found to have COVID-19 and TTP. 

We present a case of a 40-year-old female with no past medical history who presented to the Emergency Department with complaints of abdominal pain, nausea, vomiting, and dark urine. The patient workup revealed a platelet count of 4000. The patient was also noted to be COVID-19 positive. Upon further workup, the TTP diagnosis was confirmed. She responded appropriately to plasmapheresis and steroids.

COVID-19 seems to be linked to a wide range of hematologic conditions including but not limited to TTP. In view that TTP can have significant mortality if untreated, we must be suspicious about this condition in COVID-19 cases. The aim of this case report is to highlight the importance of having a low threshold for making a diagnosis of TTP if labs are significant for hemolytic anemia. Our aim is also to emphasize that the treatment should be initiated if schistocytes are seen on the peripheral smear without awaiting laboratory results confirming low levels of ADAMTS13, given the fatal nature of the condition if left untreated.

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.

Predictors of relapse and preventative strategies in immune thrombotic thrombocytopenic purpura

INTRODUCTION

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune blood disorder, which presents with microangiopathic hemolytic anemia, thrombocytopenia, and microvascular thrombosis and is caused by severe deficiency of ADAMTS13. iTTP may result in both acute and chronic complications and is rapidly fatal without expedient treatment. Life-time risk of relapse is approximately 40%.

AREAS COVERED

A number of predictors of relapse has been described in the literature. The most well-studied predictor of relapse is persistent ADAMTS13 deficiency; however, it is not a perfect marker. Relapse can be prevented by treatment with immunosuppressive medications, with rituximab being the most studied.

EXPERT OPINION

Patients who recover from iTTP should be regularly assessed, including with ADAMTS13 activity testing. The optimal frequency of assessments has not been established, but every 3 months is recommended. Considering the potential for significant organ damage and mortality associated with iTTP relapse, patients in remission and with persistent ADAMTS13 activity of 10-20% should be prophylactically treated with immunosuppression. Additional markers to precisely identify patients at higher risk of relapse are needed.

A case for consideration by apheresis practitioners: Melanoma and PD-1 inhibitor treatment in a patient with multiple relapses of immune thrombotic thrombocytopenic purpura

Thrombotic Thrombocytopenic Purpura (TTP) is a rare life-threatening disease caused by ADAMTS-13 deficiency. Up to forty percent of patients with TTP relapse, and most relapse within eight years of their first presentation. This case report describes a patient with an aggressive course of TTP who subsequently developed metastatic melanoma while receiving prophylactic rituximab. Limited data exists regarding the potential for malignancy in patients receiving Rituximab for benign conditions. This is the first published case of melanoma in a TTP patient treated with rituximab. Melanoma treatment with PD-1 inhibitors is also associated with worsening of pre-existing autoimmune conditions. In this case, a splenectomy resulted in a durable remission despite treatment with PD-1 inhibitor.

Beyond plasma exchange: novel therapies for thrombotic thrombocytopenic purpura

The advent of plasma exchange has dramatically changed the prognosis of acute thrombotic thrombocytopenic purpura (TTP). Recent insights into TTP pathogenesis have led to the development of novel therapies targeting pathogenic anti-ADAMTS13 antibody production, von Willebrand factor (VWF)-platelet interactions, and ADAMTS13 replacement. Retrospective and prospective studies have established the efficacy of rituximab as an adjunct to plasma exchange for patients with acute TTP, either upfront or for refractory disease. Relapse prevention is a major concern for survivors of acute TTP, and emerging data support the prophylactic use of rituximab in patients with persistent or recurrent ADAMTS13 deficiency in clinical remission. Capalcizumab, a nanobody directed against domain A1 of VWF that prevents the formation of VWF-platelet aggregates, recently completed phase 2 (TITAN) and 3 (HERCULES) trials with encouraging results. Compared with placebo, caplacizumab shortened the time to platelet recovery and may protect against microthrombotic tissue injury in the acute phase of TTP, though it does not modify the underlying immune response. Other promising therapies including plasma cell inhibitors (bortezomib), recombinant ADAMTS13, N-acetyl cysteine, and inhibitors of the VWF-glycoprotein Ib/IX interaction (anfibatide) are in development, and several of these agents are in prospective clinical studies to evaluate their efficacy and role in TTP. In the coming years, we are optimistic that novel therapies and international collaborative efforts will usher in even more effective, evidence-based approaches to address refractory acute TTP and relapse prevention.

Two potentially lethal conditions of probable immune origin occurring in a pregnant woman: a case report

Background

Thrombotic thrombocytopenic purpura and peripartum cardiomyopathy are potentially lethal complications of pregnancy. We describe a case in which both of these developed in the same patient. The etiologies of both conditions remain uncertain, but they share immune hyperreactivity as a possible cause.

Case presentation

A 33-year-old Lankan primigravida gave birth at 38 weeks of gestation by cesarean section when she presented with right-sided abdominal pain and a provisional diagnosis of appendicitis. Her pain persisted postoperatively, and on the second postoperative day, she physicaly collapsed suddenly with abdominal distention. Immediate laparotomy revealed generalized oozing from the peritoneum resulting in hemoperitoneum and intestinal hemorrhage. Her laboratory reports showed microangiopathic hemolytic anemia and thrombocytopenia. She also had elevated liver enzyme, lactate dehydrogenase, and creatinine concentrations. A diagnosis of thrombotic thrombocytopenic purpura was made. After a steady recovery, she was discharged from the hospital on the 16th postoperative day, but 12 hours later, she was readmitted with acute-onset progressively worsening shortness of breath. Echocardiography confirmed peripartum cardiomyopathy. She was treated with a bromocriptine and heart failure regimen. At 6 weeks postpartum, her laboratory test results and cardiac function had improved.

Conclusions

A possible autoimmune association might have caused both conditions in our patient. This case report serves as a warning message that pregnant women with one possible condition with autoimmune association could go on to develop other similar conditions.

Approach to management of thrombotic thrombocytopenic purpura at university of cincinnati

Thrombotic Thrombocytopenic Purpura (TTP) is a rare hematologic emergency, congenital or acquired, characterized by ischemic damage of various organs because of platelet aggregation. It is the common name for adults with microangiopathic hemolytic anemia, thrombocytopenia, with or without neurologic or renal abnormalities, and without another etiology; children without renal failure are also described as TTP. Plasma exchange (PE) is the main stay of treatment in combination with steroids and immunosuppressive therapies. The monoclonal antibody against CD20 Rituximab decreases the production of antibodies from B lymphocytes and it is used for antibodies-mediated diseases including TTP. We present our data on retrospective analysis of rituximab in treatment of TTP at University of Cincinnati in a series of 22 patients from 1997 to 2009. Our results showed that PE with immunosuppressive therapy resulted in decreased duration of PE, relapse rate, and increased duration of remission in patients with TTP.

Long term outcome and sequelae in patients after acute thrombotic thrombocytopenic purpura episodes

We report on 21 patients with idiopathic thrombotic thrombocytopenic purpura (TTP) whose courses of disease have been followed from the respective diagnosis until now. They had a documented ADAMTS13 activity below 5%, a high autoantibody titer and detectable ultralarge von Willebrand factor (VWF) multimers during their episodes. The initial diagnosis was based on clinical symptoms and on laboratory parameters: thrombocytopenia, haemolytic anaemia, schistocytes and an increased LDH level. 103 acute clinical episodes of 21 TTP-patients during a time period of 30 years are described. Case histories, comorbidities and sequelae were retrospectively documented.

RESULTS, CONCLUSION

Although patients are consistently in a prothrombotic status, clinical acute manifestations only occur after triggering. Most common trigger factors are gastrointestinal infections and pregnancy. The relapse risk per month is 0.026; men have a higher risk for relapses (0.044) than women (0.021). Patients recover physically well, except for renal insufficiency in four cases. Nevertheless, major portion of patients suffers persistently from depression, anxiety disorders and persistent neurocognitive impairments.

Cyclosporin A therapy on idiopathic thrombotic thrombocytopenic purpura in the relapse setting: two case reports and a review of the literature

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease, characterized by microangiopathic hemolytic anemia, thrombocytopenia, fever, neurologic disturbances, and renal failure. Plasma therapy has dramatically improved prognosis of TTP, whereas recurrent acute episodes still occur in approximately 40% of patients. Moreover, patients with acquired ADAMTS13 deficiency, which is a significant factor for relapse, may require additional immunosuppressive treatment to get a durable remission.

STUDY DESIGN AND METHODS

We hereby report two patients with a history of relapsed idiopathic TTP, who both received cyclosporin A (CSA) as a prophylactic manner after the remission was achieved. We also discuss the efficacy of CSA in patients with relapsed idiopathic TTP with a review of the published literature.

RESULTS

Under CSA therapy, both patients maintained their clinical remission state, and the ADAMTS13 levels were normalized.

CONCLUSION

To conclude, CSA therapy may be useful for the prevention of relapsed idiopathic TTP in patients with a history of frequent relapses.

[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.

Efficacy and safety of rituximab in adult patients with idiopathic relapsing or refractory thrombotic thrombocytopenic purpura: results of a Spanish multicenter study

BACKGROUND

Between 30% and 60% of patients with thrombotic thrombocytopenic purpura (TTP) relapse and mortality remains at 15-20%. Limited clinical data suggest that the administration of anti-CD20 antibody (rituximab) may be useful in preventing acute refractory and chronic relapsing TTP.

DESIGN AND METHODS

We studied the clinical response to rituximab in 24 adult patients (median age 42 years, range 24-72 years) from 15 Spanish centers with an acute refractory (14 patients) or acute relapsing (10 patients) episode of idiopathic TTP. On admission, every patient received daily plasma exchange (PE). Rituximab was administered at a dose of 375 mg/m(2) weekly for a median of 13 days (range 0-57 days) after starting PE for a median of 4 doses (range 1-8 doses).

RESULTS

No severe acute or delayed toxicity was observed in the patients treated with rituximab. Three (12.5%) patients died because of TTP-related causes. The remaining 21 (87.5%) patients achieved complete remission in a median of 21 days (range 2-35 days) after initiating rituximab. After a median follow-up of 30 months (range 7.5-74 months), 18 patients are in remission and 3 patients have relapsed at 7, 29, and 29 months.

CONCLUSIONS

Rituximab appears to be a safe, effective therapy and has a high response rate for the treatment of acute refractory or relapsing idiopathic TTP in adult patients.

Membrane plasma exchange for the treatment of thrombotic thrombocytopenic purpura

The aim of our report is to present our 11-year experience with therapeutic membrane plasma exchange therapy for the treatment of idiopathic thrombotic thrombocytopenic purpura syndrome (TTP). In 56 patients, membrane plasma exchange therapy was initiated immediately and performed once or twice daily until the platelet count normalized. During each plasma exchange procedure, 1-1.5 plasma volumes (3606 +/- 991 mL) were replaced with fresh frozen plasma. In 37 females and 19 males (44 +/- 21 years), 1066 plasma exchange procedures were performed. The average duration of treatment was 23 +/- 17 days. The average number of plasma exchanges was 19 +/- 17 per patient. Renal impairment was detected in 36% of patients. At the initiation of plasma exchange treatment, the average platelet count was 31 +/- 30 x 10(9)/L and reached 199 +/- 95 x 10(9)/L thereafter. Fifty-two of 56 (93%) patients demonstrated an excellent response to plasma exchange therapy, of whom 48 patients (86%) attained complete remission with a platelet count of more than 100 x 10(9)/L. Four patients died soon after the initiation of plasma exchange therapy, when only 1-3 procedures had been performed. During the follow-up period, six patients with complete remission had 1-5 subsequent relapses each year. One of them died of acute hemolytic reaction during the tapering of plasma exchange procedures. Three patients underwent additional splenectomy. Our experience with primary TTP supports the plasma exchange treatment with fresh frozen plasma as a mandatory, up-to-date therapy. Close monitoring during all 1066 procedures showed no serious side-effects.

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.

Intravenous immunoglobulin as an adjunct to plasma exchange for the treatment of chronic thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease. Therapeutic plasma exchange (TPE) is the most effective therapy; however, despite TPE, about one-third of TTP patients will relapse. A subset of patients with TTP has antibodies to ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) and may become resistant to conventional treatments. We describe a patient with TTP and high-titre anti-ADAMTS13 antibodies who developed a chronic, relapsing course of TTP despite frequent TPE. Once adjuvant treatment with intravenous immunoglobulin (IVIG) was added, remission was achieved. Even during remission, anti-ADAMTS13 antibodies remained elevated. We conclude that IVIG may sustain remission in some patients with chronic, relapsing TTP.

Mycophenolate mofetil in a case of relapsed, refractory thrombotic thrombocytopenic purpura

A case of relapsing and refractory thrombotic thrombocytopenic purpura received mycophenolate mofetil (MMF) to attempt to maintain remission. The possible use of MMF in thrombotic thrombocytopenic purpura is discussed.

Journey in reverse: TTP from bedside to blood bank to bench

Thrombotic thrombocytopenic purpura (TTP) is the most extensive and dangerous intravascular platelet clumping disorder. For more than a half-century after its initial recognition, mortality was near 100% and the etiology totally obscure. Then, in the late 1970s to early 1980s, empiric, but successful, therapy by a few clinician/blood bank partnerships was followed by sudden laboratory insight into pathophysiology. The discussion that follows was prepared in conjunction with the 2006 Francis Morrison, M.D., Memorial Lecture at the 27th Annual Meeting of the American Society for Apheresis.

Outcomes in the treatment of thrombotic thrombocytopenic purpura with splenectomy: a retrospective cohort study

The mainstay of treatment for thrombotic thrombocytopenic purpura (TTP) is plasma exchange (PE), but the role of splenectomy is still undefined. The records of all patients with TTP at a single center over a 20-year period were retrospectively reviewed. Response to plasma exchange was determined. The outcome of patients treated with splenectomy in the setting of TTP was evaluated. Sixty-one patients had been treated for TTP. Thirty-nine patients (64%) achieved complete remission (CR) with PE, nineteen (31%) of these achieving sustained CR and seventeen (28%) with relapsed TTP. Twenty patients (33%) had PE refractory TTP and two patients (3%) had PE dependent TTP. During this time period, 10 patients (16%) underwent splenectomy, four patients (7%) for PE dependent TTP, three (5%) for relapsed TTP, and three (5%) for refractory TTP. All of the patients achieved CR after splenectomy. Two patients who had undergone splenectomy had subsequent relapses, both with previously relapsed TTP. In relapsed patients the relapse rate after splenectomy was 0.27 events per patient year compared to 0.6 events per patient year before splenectomy. Median follow-up after splenectomy was 19 months (range 0.13-90 months). In conclusion, relapses in TTP can be managed successfully with additional PE or with splenectomy. PE dependent or refractory TTP can be successfully treated with splenectomy.

Thrombotic Thrombocytopenic Purpura: aetiology, pathophysiology and treatment

Thrombotic thrombocytopenic purpura (TTP) is a rare disorder whose varied clinical manifestations result from the formation of platelet-rich thrombi within the microvasculature and consequent tissue ischaemia. This review will outline how, in the eighty years since its initial description, scientific discoveries have not only led to a deeper understanding of the fundamental pathophysiology of TTP, but have also contributed to advances in the clinical management of this condition. Current research in this field will hopefully provide the basis for the design and development of novel therapeutic strategies.

Cardiogenic shock complicates successful treatment of refractory thrombotic thrombocytopenia purpura with rituximab

BACKGROUND

Treatment of thrombotic thrombo-cytopenia purpura (TTP) with daily therapeutic plasma exchange (TPE) may be accompanied by a variety of adjunctive interventions including most recently rituximab. Rituximab, a murine and human monoclonal antibody directed against CD20 antigen on B lymphocytes, is primarily used for treatment of non-Hodgkin's lymphomas. Because of severe and fatal infusion reactions including heart failure, rituximab carries a boxed warning.

CASE REPORT

A 20-year-old female presented with TTP. She underwent 17 daily (1 day skipped) TPE. Her platelet (PLT) count reached 150 x 10(9) per L and then gradually declined to 36 x 10(9) per L despite continuing TPE. Because of the refractory behavior of her disease, rituximab was administered. After the rituximab infusion, she developed a nonproductive cough which progressed to a productive cough, acute respiratory failure, chest pain, and hypotension and was moved to intensive care for management of biventricular cardiogenic shock (ejection fraction was 5%-10%). Once stable in the intensive care unit, TPE was resumed. Her PLT count reached 241 x 10(9) per L, and her lactate dehydrogenase decreased to normal after four TPEs. Her heart failure completely resolved and she was discharged. Rituximab was added to her medical record as a drug allergy.

CONCLUSION

Refractory TTP has been reported to respond favorably to rituximab when used as an adjunct. Interventions, however, can also carry significant risk as illustrated by the cardiogenic shock in our patient. Use of rituximab for refractory TTP should follow a careful assessment of benefits.

Splenectomy for the treatment of thrombotic thrombocytopenic purpura

Plasma exchange is the treatment of choice for patients with thrombotic thrombocytopenic purpura (TTP) and results in remission in >80% of the cases. Treatment of patients who are refractory to plasma therapy or have relapsing disease is difficult. Splenectomy has been a therapeutic option in these conditions but its value remains controversial. We report on a series of 33 patients with TTP who were splenectomised because they were plasma refractory (n = 9) or for relapsed disease (n = 24). Splenectomy generated prompt and unmaintained remissions in all except five patients, in whom remission was delayed (n = 4) or who died with progressive disease (n = 1). Four postoperative complications occurred: one pulmonary embolism and three surgical complications. Median follow-up after splenectomy was 109 months (range 28-230 months). The overall postsplenectomy relapse rate was 0.09 relapses/patient-year and the 10-year relapse-free survival (RFS) was 70% (95% CI 50-83%). In the patients with relapsing TTP, relapse rate fell from 0.74 relapses/patient-year before splenectomy to 0.10 after splenectomy (P < 0.00001). Two patients died from first postsplenectomy relapse. Although these results are based on retrospective data and that the relapse rate may spontaneously decrease with time, we conclude that splenectomy, when performed during stable disease, has an acceptable safety profile and should be considered in cases of plasma refractoriness or relapsing TTP to reach durable remissions and to reduce or prevent future relapses.

Thrombotic thrombocytopenic purpura

This overview summarizes the history of thrombotic thrombocytopenic purpura (TTP) from its initial recognition in 1924 as a most often fatal disease to the discovery in 1997 of ADAMTS-13 deficiency as a major risk factor for acute disease manifestation. The cloning of the metalloprotease, ADAMTS-13, an essential regulator of the extremely adhesive unusually large von Willebrand factor (VWF) multimers secreted by endothelial cells, as well as ADAMTS-13 structure and function are reviewed. The complex, initially devised assays for ADAMTS-13 activity and the possible limitations of static in vitro assays are described. A new, simple assay using a recombinant 73-amino acid VWF peptide as substrate will hopefully be useful. Hereditary TTP caused by homozygous or double heterozygous ADAMTS-13 mutations and the nature of the mutations so far identified are discussed. Recognition of this condition by clinicians is of utmost importance, because it can be easily treated and--if untreated--frequently results in death. Acquired TTP is often but not always associated with severe, autoantibody-mediated ADAMTS-13 deficiency. The pathogenesis of cases without severe deficiency of the VWF-cleaving protease remains unknown, affected patients cannot be distinguished clinically from those with severely decreased ADAMTS-13 activity. Survivors of acute TTP, especially those with autoantibody-induced ADAMTS-13 deficiency, are at a high risk for relapse, as are patients with hereditary TTP. Patients with thrombotic microangiopathies (TMA) associated with hematopoietic stem cell transplantation, neo-plasia and several drugs, usually have normal or only moderately reduced ADAMTS-13 activity, with the exception of ticlopidine-induced TMA. Diarrhea-positive-hemolytic uremic syndrome (D+ HUS), mainly occurring in children is due to enterohemorrhagic Escherichia coli infection, and cases with atypical, D- HUS may be associated with factor H abnormalities. Treatment of acquired idiopathic TTP involves plasma exchange with fresh frozen plasma (FFP), and probably immunosuppression with corticosteroids is indicated. We believe that, at present, patients without severe acquired ADAMTS-13 deficiency should be treated with plasma exchange as well, until better strategies become available. Constitutional TTP can be treated by simple FFP infusion that rapidly reverses acute disease and--given prophylactically every 2-3 weeks--prevents relapses. There remains a large research agenda to improve diagnosis of TMA, gain further insight into the pathophysiology of the various TMA and to improve and possibly tailor the management of affected patients.

Dissociation between the level of von Willebrand factor-cleaving protease activity and disease in a patient with congenital thrombotic thrombocytopenic purpura

Decreased von Willebrand factor (VWF)-cleaving protease activity (<5%) has been implicated in patients with congenital thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (Upshaw-Schulman syndrome) and associated with mutations within the ADAMTS13 gene. In this report, we describe longitudinal studies in a patient with congenital TTP who ultimately developed end-stage renal failure and required plasma therapy from infancy. The patient was deficient in plasma high molecular weight (HMW)-VWF multimers during acute disease but had increased amounts of the HMW-VWF multimers during periods of remission. DNA analysis of this patient detected homozygosity for the R692C mutation on exon 17 of the ADAMTS13 gene, previously linked to congenital TTP. The level of VWF-cleaving protease activity in the patient was remarkably low (<5%) throughout her disease, even after she entered complete remission. However, despite no improvement in the level of VWF-cleaving protease activity, this patient had complete resolution of disease following splenectomy and commencing hemodialysis, without need for ongoing plasma therapy. The patient has remained in remission for over 4 years. These observations suggest that there are other factors in conjunction with severe deficiency of VWF protease activity that participate in the platelet-mediated thrombotic complications and other disease manifestations of congenital TTP. In addition, it is possible that splenectomy could be an effective treatment option for some patients with severe, congenital TTP.

Rituximab for treatment of refractory/relapsing thrombotic thrombocytopenic purpura (TTP)

Plasma exchange is the standard treatment for thrombotic thrombocytopenic purpura (TTP). For patients refractory to plasma exchange, treatment options are limited and often unsuccessful. The platelet thrombi that form in acquired TTP are believed to result from the presence of procoagulant ultralarge multimers of von Willebrand factor (VWF) in the circulation due to autoantibody inhibition of VWF cleaving protease (ADAMTS-13), the enzyme that normally cleaves the ultralarge multimers. Rituximab, a chimeric monoclonal antibody against CD20, has been recognized as a useful therapy for antibody-mediated autoimmune disease. We therefore treated four patients with recurrent TTP with 2 or 4 weekly doses of rituximab in addition to corticosteroids, vincristine, plasma, or continuing plasma exchange. Three patients responded with prompt improvement in microangiopathic hemolytic anemia and thrombocytopenia, which allowed plasma exchange to be discontinued or avoided and prednisone to be rapidly discontinued. Two of the 3 responders have remained in unmaintained complete remission for 13+ months. The third patient relapsed at 13 months; a second course of rituximab and prednisone resulted in an unmaintained remission for 6+ months. All four patients were tested for ADAMTS-13 activity and its inhibitor at a point in their course when samples were available. Low ADAMTS-13 activity was noted in 3 patients tested at relapse, and the inhibitor activity was detectable in 2 patients. ADAMTS-13 activity increased during remission in one of these 2 patients although the patient had a persistence of the inhibitor. One patient tested only during remission had a normal ADAMTS-13 level. We conclude that rituximab may have a role and deserves further study in the treatment of patients with relapsing TTP.

von Willebrand factor, ADAMTS-13, and thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a severe, occlusive, microvascular "thrombotic microangiopathy" characterized by systemic platelet aggregation, organ ischemia, profound thrombocytopenia, and erythrocyte fragmentation. Failure to degrade "unusually large" (UL) von Willebrand factor (VWF) multimers as they are secreted from endothelial cells probably causes most cases of familial TTP, acquired idiopathic TTP, thienopyridine-related TTP, and pregnancy-associated TTP. The emphasis in this review is the pathophysiology of familial and acquired idiopathic TTP. In each of these entities, there is a severe defect in the function of a plasma enzyme, VWF-cleaving metalloprotease (ADAMTS-13), that normally cleaves hyper-reactive ULVWF multimers into smaller and less adhesive VWF forms. In familial TTP, mutations in the ADAMTS13 gene cause absent or severely reduced plasma VWF-cleaving metalloprotease activity. Acquired idiopathic TTP, in contrast, is the result in many patients of the production of autoantibodies that inhibit the function of ADAMTS-13. Established, evolving, and some of the unresolved issues in TTP pathophysiology will be summarized.

Recent advances in thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is characterized by microangiopathic hemolytic anemia and thrombocytopenia, accompanied by microvascular thrombosis that causes variable degrees of tissue ischemia and infarction. Intravascular coagulation is not a prominent feature of the disorder. Plasma exchange can induce remissions in approximately 80% of patients with idiopathic TTP, but patients have a much worse prognosis when thrombotic microangiopathy is associated with cancer, certain drugs, infections, or tissue transplantation. Recently, acquired autoimmune deficiency of a plasma metalloprotease named ADAMTS13 was shown to cause many cases of idiopathic TTP. This review describes our current understanding of how to use this knowledge clinically. In Section I, Dr. Joel Moake describes the presentation of thrombotic microangiopathy, emphasizing the pathophysiology of idiopathic TTP. Platelets adhere to ultra-large (or "unusually large") von Willebrand factor (ULVWF) multimers that are immobilized in exposed subendothelial connective tissue and secreted into the circulation in long "strings" from stimulated endothelial cells. ADAMTS13 cleaves ULVWF multimers within growing platelet aggregates under flowing conditions, and this normally limits platelet thrombus formation. If ADAMTS13 is absent, either congenitally or due to acquired autoantibodies, platelet-rich microvascular thrombosis proceeds unchecked and TTP ensues. Plasma exchange is effective therapy for idiopathic TTP, probably because it replenishes the deficient ADAMTS13 and removes some of the pathogenic autoantibodies and endothelial-stimulating cytokines. Some patients have a type of thrombotic microangiopathy after transplantation/chemotherapy but do not have severe ADAMTS13 deficiency. The pathogenesis of their disease must differ but remains poorly understood. In Section II, Dr. Toshiyuki Miyata describes recent advances in assay methods that should facilitate routine laboratory testing of ADAMTS13 for patients with thrombotic microangiopathy. ADAMTS13 cleaves a single Tyr-Met bond in domain A2 of the VWF subunit. ADAMTS13 assays based on the cleavage of plasma VWF multimers have been used extensively but require considerable time and expertise to perform. A recombinant substrate containing 73 amino acid residues of VWF domain A2 has been devised that allows short incubation times and rapid product detection by gel electrophoresis or immunoassay. These results should encourage the development of even simpler assays that can be performed in most clinical laboratories. In Section III, Dr. James George provides an update on the long-term prospective study of thrombotic microangiopathy in the Oklahoma TTP-HUS Registry. At presentation, the clinical distinction between idiopathic TTP, various forms of secondary thrombotic microangiopathy, and even Shiga toxin-associated hemolytic uremic syndrome (HUS) can be problematic because the symptoms and laboratory findings often overlap. Consequently, plasma exchange usually is administered to any patient with thrombotic microangiopathy if there is doubt about the cause. The role of ADAMTS13 testing in choosing therapy remains uncertain, but the results do appear to have prognostic significance. Severe ADAMTS13 deficiency is specific for idiopathic TTP and identifies a subgroup with a high likelihood of response to plasma exchange, and high-titer ADAMTS13 inhibitors correlate strongly with a high risk of relapsing disease. Patients with normal ADAMTS13 activity have a much worse prognosis, although many factors probably contribute to this difference. Longitudinal study of these patients will continue to clarify the relationship of ADAMTS13 deficiency to the clinical course of thrombotic microangiopathy.

Role of splenectomy in patients with refractory or relapsed thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) was once uniformly fatal. Therapeutic plasma exchange in combination with immunosuppressive and anti-platelet agents, however, have resulted in improved survival rates of greater than 80% for patients with TTP. In spite of aggressive plasma exchange and adjuvant therapy, a number of TTP patients are refractory to treatment. In addition, up to 40% of TTP patients who initially respond to therapy eventually relapse. Alternative therapies such as splenectomy have been used with varying degrees of success in refractory and relapsing TTP patients. The usefulness of splenectomy in preventing relapse of TTP or treating those patients who are refractory to plasma exchange remains controversial. We present a single institution's experience with 14 patients who underwent splenectomy for refractory (six patients) or relapsed (eight patients) TTP since 1984. In both patient groups, splenectomy induced stable long-term remissions. Six of six (100%) patients who were refractory to plasma exchange, survived to be discharged from the hospital, apparently free of disease. Four of eight patients (50%) who had a splenectomy for relapsing TTP went into a complete remission and had no further relapses of their disease. Moreover, in relapsing patients who failed to experience long-term remission, the relapse rate after splenectomy was 0.3 events per patient year compared to 1.0 events per patient year prior to splenectomy. We conclude that splenectomy is a reasonable treatment option for TTP patients refractory to standard plasma exchange therapy or who have experienced multiple and/or complicated relapses. We believe this is the first series that demonstrates efficacy of splenectomy in plasma exchange-refractory TTP.

Thrombotic thrombocytopenic purpura: the systemic clumping "plague"

In thrombotic thrombocytopenic purpura (TTP), a multimeric form of von Willebrand factor (vWf) that is larger than ordinarily found in the plasma causes systemic platelet aggregation under the high-shear conditions of the microcirculation. A divalent cation-activated, vWf-cleaving metalloprotease that metabolizes large vWf multimers to smaller forms in normal plasma is severely reduced or absent in most patients with TTP. The vWf-cleaving metalloprotease either is not produced or is defective in children with chronic relapsing TTP. When the enzyme is provided by the infusion of normal plasma, these patients remain free of TTP symptoms for about three weeks. An IgG autoantibody to the vWf-cleaving metalloprotease is found transiently in many adult patients with acute idiopathic, recurrent, and ticlopidine/clopidogrel-associated TTP. These patients require plasma exchange, i.e., concurrent replacement of the inhibited vWf-cleaving metalloprotease by plasma infusion and plasmapheresis. The vWf-cleaving metalloprotease is present in fresh-frozen plasma, in cryoprecipitate-depleted plasma (cryosupernatant), and in plasma that has been treated with solvent and detergent. The pathophysiology of platelet aggregation in bone marrow transplantation/chemotherapy-associated thrombotic microangiopathy, and in the hemolytic-uremic syndrome, is not established. In neither condition is there a severe decrease in plasma vWf-cleaving metalloprotease activity.

Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are multisystemic disorders that are characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic manifestations, resulting from platelet agglutination in the arterial microvasculature. Until the introduction of plasma-based therapy, TTP was associated with a mortality rate greater than 90%. Current outcomes of TTP and HUS have improved dramatically with the use of plasma exchange, which should be initiated promptly at diagnosis. Recent evidence suggests that deficiency of a specific plasma protease responsible for the physiologic degradation of von Willebrand factor plays a pathogenic role in a substantial proportion of familial and acute idiopathic cases of TTP. Although multiple triggers, such as infection, drugs, cancer, chemotherapy, bone marrow transplantation, and pregnancy, are recognized, knowledge of the pathogenesis of TTP and HUS in relationship to these disorders remains incompletely understood and continues to evolve. While uncommon, TTP and HUS are of considerable clinical importance because of their abrupt onset, fulminant clinical course, and high morbidity and mortality in the absence of early recognition and treatment.

New aspects in the pathogenesis and treatment of thrombotic thrombocytopenic purpura and hemolytic uremic syndrome

The thrombotic microangiopathy (TM) syndromes, thrombotic thrombocytopenic purpura and the hemolytic uremic syndrome, are a rare and heterogeneous group of disorders characterized by widespread microvascular thrombosis and end organ injury. Decades of descriptive studies have defined clinical subsets of TM syndromes by clinical and laboratory features. Despite many advances, however, progress towards understanding of the etiology and pathogenesis of TM disorders remains limited. The rarity of occurrence and lack of natural animal models of TM syndromes have hampered progress in experimental and clinical studies. Treatment remains essentially empirical and options are limited. However, recent advances in the genetic and molecular understanding of subsets of TM disorders and the development of relevant animal models offer new resources to explore the pathogenic mechanisms. With these new advances more effective and individualized treatments for TM syndromes can be developed.

Aetiology and pathogenesis of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome: the role of von Willebrand factor-cleaving protease

Thrombotic thrombocytopenic purpura (TTP) and haemolytic uraemic syndrome (HUS) are today often regarded as variants of one syndrome denoted as TTP/HUS, characterized by thrombocytopenia caused by intravascular platelet clumping, microangiopathic haemolytic anaemia, fever, renal abnormalities and neurological disturbances. Unusually large von Willebrand factor multimers have been observed in plasma from patients with chronic relapsing forms of TTP. Their appearance in patients with classic TTP is caused by deficiency of a specific von Willebrand factor-cleaving protease. A constitutional deficiency of this protease has consistently been found in familial cases of TTP, whereas in acquired TTP the protease deficiency is caused by the presence of an inhibiting autoantibody. A normal activity of von Willebrand factor-cleaving protease has been established in patients with HUS. In this chapter, we report 23 cases with severe constitutional protease deficiency: about one half of these patients had their first acute episode as children, whereas the other half had their first TTP event at an adult age, several of them during their first pregnancy. Two of these 23 individuals with congenital protease deficiency, both older than 35 years, have never had an acute TTP event. These results indicate that a deficiency of von Willebrand factor-cleaving protease alone is not sufficient to cause acute TTP. Patients with long-lasting dormant protease deficiency have been found to experience multiple relapses of TTP after having had their first acute episode. In one protease-deficient, plasma-dependent patient with chronic relapsing TTP, we estimated that 5% of normal protease activity is sufficient to remove the most adhesive von Willebrand factor multimers and prevent the formation of platelet microthrombi. The deficiency of von Willebrand factor-cleaving protease is a very strong risk factor for TTP, but the development of an acute bout requires a trigger, possibly causing the activation or apoptosis of endothelial cells in the microcirculation. It is unclear whether anti-endothelial cell antibodies, cytokines or other agents are involved in triggering thrombotic microangiopathy. The release of platelet calpain (and/or other proteases), leading to a degradation of von Willebrand factor and to platelet aggregation, has been reported in patients during their acute TTP episode. It is unknown whether calpain directly triggers an acute event or whether it merely reflects its release during the aggregation of platelets by the unusually large von Willebrand factor multimers. With regard to the heterogeneous aetiology of thrombotic microangiopathies, requiring distinct therapeutic measures, a new classification of thrombotic microangiopathy should replace the current, frequently inappropriate clinical discrimination between TTP and haemolytic uraemic syndrome.

[Idiopathic thrombotic thrombocytopenic purpura or Moschowitz syndrome: current physiopathologic and therapeutic perspectives]

INTRODUCTION

The objective of this work was to review current data about the physiopathology, clinical features, and treatment of thrombotic thrombocytopenic purpura (Moschowitz's syndrome).

CURRENT KNOWLEDGE AND KEY POINTS

Thrombotic thrombocytopenic purpura is a rare disorder characterized by widespread thrombotic injuries of platelets in the microcirculation. Its physiopathology has been elucidated recently. Evidence of a deficiency of Von Willebrand's factor-cleaving protease would be due to either IgG antibodies in the acute form of the disease or constitutional deficiency in the chronic form of the disease.

FUTURE PROSPECTS AND PROJECTS

Plasma exchange is the current reference treatment. However, in the light of recent publications, either infusions of concentrates of purified enzyme or more intensive immunosuppressive therapy would be more specific.

How I treat patients with thrombotic thrombocytopenic purpura–hemolytic uremic syndrome

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are, in adults, clinically and pathologically indistinguishable except for the severity of renal failure. They are best described as a single disorder, TTP-HUS, because the diagnostic evaluation and initial management are the same. Treatment with plasma exchange, available for more than 20 years, has dramatically altered the course of disease in adults with TTP-HUS. Plasma exchange has improved survival rates from 10% to between 75% and 92%, creating urgency for the initiation of treatment. This has resulted in decreased stringency of diagnostic criteria, which in turn has resulted in a broader spectrum of disorders for which the diagnosis of TTP-HUS is considered. Long-term follow-up has revealed increasing frequencies of relapse and of chronic renal failure. Although the increased survival rate is dramatic and recent advances in understanding the pathogenesis of these syndromes are remarkable, clinical decisions remain empirical. Therefore, the management decisions for patients with suspected TTP-HUS rely on individual experience and opinion, resulting in many different practice patterns. Multipractice clinical trials are required to define optimal management.

How I treat patients with thrombotic thrombocytopenic purpura–hemolytic uremic syndrome

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are, in adults, clinically and pathologically indistinguishable except for the severity of renal failure. They are best described as a single disorder, TTP-HUS, because the diagnostic evaluation and initial management are the same. Treatment with plasma exchange, available for more than 20 years, has dramatically altered the course of disease in adults with TTP-HUS. Plasma exchange has improved survival rates from 10% to between 75% and 92%, creating urgency for the initiation of treatment. This has resulted in decreased stringency of diagnostic criteria, which in turn has resulted in a broader spectrum of disorders for which the diagnosis of TTP-HUS is considered. Long-term follow-up has revealed increasing frequencies of relapse and of chronic renal failure. Although the increased survival rate is dramatic and recent advances in understanding the pathogenesis of these syndromes are remarkable, clinical decisions remain empirical. Therefore, the management decisions for patients with suspected TTP-HUS rely on individual experience and opinion, resulting in many different practice patterns. Multipractice clinical trials are required to define optimal management.