Alemtuzumab-induced immune-mediated thrombotic thrombocytopenic purpura: A newly described drug-related autoimmune disease.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening disease that may result from drug exposure. We report a case of iTTP occurring in a 39-year-old patient, 45 months following introduction of the anti-CD52 lymphoid cell depleting monoclonal antibody alemtuzumab, to treat a relapsing-remitting multiple sclerosis. Treatment consisted in plasma exchange, corticosteroids and caplacizumab, allowing clinical remission 3 months after the diagnosis, attested by the absence of thrombocytopenia and recovery of ADAMTS-13 activity. As other autoimmune disorders, iTTP may occur following alemtuzumab. This diagnosis should be suspected in patients with features of thrombotic microangiopathy following this treatment.

[Endothelial dysfunction in thrombotic thrombocytopenic purpura: therapeutic perspectives]. / Dysfonction endothéliale au cours du Purpura Thrombotique Thrombocytopénique : un nouvel axe de prise en charge ?

Immune Thrombotic Thrombocytopenic Purpura (iTTP) is a rare but severe disease with a mortality rate of almost 100 % in the absence of adequate treatment. iTTP is caused by a severe deficiency in ADAMTS13 activity due to the production of inhibitory antibodies. Age has been shown to be a major prognostic factor. iTTP patients in the elderly (60yo and over) have more frequent organ involvement, especially heart and kidney failures compared with younger patients. They also have non-specific neurologic symptoms leading to a delayed diagnosis. Factors influencing this impaired survival among older patients remain unknown so far. Alteration of the functional capacity of involved organs could be part of the explanation as could be the consequences of vascular aging. In fact, severe ADAMTS13 deficiency is necessary but likely not sufficient for iTTP physiopathology. A second hit leading to endothelial activation is thought to play a central role in iTTP. Interestingly, the mechanisms involved in endothelial activation may share common features with those involved in vascular aging, potentially leading to endothelial dysfunction. It could thus be interesting to better investigate the causes of mid- and long-term mortality among older iTTP patients to confirm whether inflammation and endothelial activation really impact vascular aging and long-term mortality in those patients, in addition to their presumed role at iTTP acute phase. If so, further insights into the mechanisms involved could lead to new therapeutic targets.

[Acquired angioedema due to C1-inhibitor deficiency: CREAK recommendations for diagnosis and treatment]. / Angiœdèmes par déficit acquis en C1-inhibiteur : recommandations du CREAK pour le diagnostic et la prise en charge.

Acquired angioedema with C1-inhibitor deficiency is a rare and peculiar entity belonging to the spectrum of bradykinin angioedemas. It usually occurs in subjects over 60 years old, and is mostly associated with a B-cell lymphoid hemopathy or a monoclonal gammopathy. The diagnosis relies on at least one angioedema episode, lasting more than 24 h, and on the decrease of functional C1-inhibitor. Low C1q is observed in 90% of patients, and an anti C1-inhibitor antibody is found in 50% of patients. The treatment of severe attacks relies on icatibant or C1-inhibitor perfusions. Long term prophylaxis in patients with frequent attacks requires treatment of the associated hemopathy if so. In case of idiopathic angioedema, tranexamic acid and danazol may be used, provided that there is-no thrombophilia; as well as rituximab as second-line treatment. Inhibitors of kallikrein still need to be evaluated in this therapeutic indication.

[Venous thrombo-embolism during immune-mediated thrombotic thrombocytopenic purpura is prevalent in patients with a prolonged treatment with therapeutic plasma exchange]. / La maladie thrombo-embolique veineuse au cours du purpura thrombotique thrombocytopénique autoimmun est associée à un traitement prolongé par échanges plasmatiques.

INTRODUCTION: Thrombotic thrombocytopenic purpura (TTP) is a devastating disease characterized by disseminated microvascular thrombosis. Despite pro-thrombotic predisposing conditions, the prevalence of macrovascular venous thrombosis event (VTE) in immune-mediated TTP (iTTP) has rarely been assessed. METHODS: We reviewed data of all iTTP patients of the French reference Center for thrombotic microangiopathies registry prospectively enrolled through a 10-year period, between 2008 and 2018. Venous thrombosis included either thrombosis of central venous catheter, symptomatic deep venous thrombosis of the limbs or pulmonary embolism. RESULTS: Forty-eight (12.7%) VTE were diagnosed. VTE was diagnosed after a median time of 7 [IQR, 3-16] days following the first therapeutic plasma exchange (TPE) and consisted mainly in catheter-related thrombosis (73%), and to a lesser extend symptomatic deep venous thrombosis (16%), proximal pulmonary embolism (8%) and splanchnic vein thrombosis (2%). Cases with VTE (VTE+ cases), required more TPE to achieve remission (P < 0.01), and the total volume of plasma required to achieve remission was larger (P < 0.01) than for VTE- cases. There was also a trend for more rituximab use in the VTE+ cases as compared to the VTE- cases (47% vs 33%; respectively; P = 0.07). Curative anticoagulation was started in 38 cases (79%), while 6 VTE cases did not receive any antithrombotic agents, and catheter was systematically removed when catheter-related thrombosis was diagnosed. VTE+ cases had a higher number of inserted central venous catheters than VTE- cases (P < 0.05). CONCLUSION: VTE is a frequent condition occurring during iTTP management and is observed when patients require a prolonged treatment with daily TPE and multiple catheter insertions. Therapeutic strategies aimed at reducing the duration of TPE treatment in iTTP should substantially reduce this complication.

Prognosis of Lymphoma in Patients With Known Inflammatory Bowel Disease: A French Multicentre Cohort Study.

BACKGROUND AND AIMS: The prognosis of lymphoma that occurs in patients with inflammatory bowel disease [IBD] is poorly known. METHODS: A multicentre retrospective cohort analysis was done in seven French tertiary centres from 1999 to 2019. Only lymphoma occurring in patients with previous established diagnosis of IBD were analysed. The primary outcome was progression-free survival at 3 years. RESULTS: A total of 52 patients [male 65%, Crohn's disease 79%, median age 48.3 years, median duration of IBD 10.1 years] were included, of whom 37 had been previously exposed to immunosuppressants and/or biologics for at least 3 months and 20 had primary intestinal lymphomas. The lymphoma histological types were: diffuse large B cell lymphomas [N = 17], Hodgkin lymphomas [N = 17], indolent B cell lymphomas [N = 12], and others including T cell lymphomas, mantle cell lymphomas, and unclassifiable B cell lymphoma [N = 6]. The median follow-up after lymphoma was 5.1 years (interquartile range [IQR] 4-7.8). Progression-free survival at 3 years was 85% in the overall population (95% confidence interval [CI] 75%-96%) with no significant difference between the exposed and unexposed group, 79% for patients exposed to immunosuppressants and/or biologics [95% CI 67%-94%], and 83% for patients diagnosed with primary intestinal lymphoma [95% CI 67%-100%]. No relapse of IBD has been observed during chemotherapy. The IBD relapse rate at the end of the last chemotherapy cycle was 23% at 3 years [95% CI 11%-39%] in the overall population. CONCLUSIONS: In this large cohort, the prognosis for lymphomas occurring in IBD appears to be good and similar to what is expected, irrespective of the exposure to biologics and/or immunosuppressants.

Factors associated with tuberculosis-associated haemophagocytic syndrome: a multicentre case-control study.

SETTING: Tuberculosis (TB) is a potential trigger of haemophagocytic syndrome (HS) but little is known about the features of TB-associated HS.OBJECTIVE: To assess the risk factors associated with HS in patients with TB.DESIGN: We performed a multicentre case-control study assessing the medical records of adult patients diagnosed with proven TB with (TB/HS+) or without (TB/HS-) associated HS.RESULTS: Twenty-one patients with TB/HS+ (24% women, median age, 37 years [IQR 30-48]) were included in the study. Eleven patients (52%) were infected with human immunodeficiency virus and seven patients (33%) were immunocompromised due to other reasons. TB was disseminated in 17 patients (81%). Compared with 50 control TB patients (TB/HS-), patients with TB/HS+ were more likely to be immunocompromised (86% vs. 18%; P < 0.001) and to present with disseminated TB (80% vs. 12%; P < 0.001). The outcome was poorer in patients with TB/HS+, with a higher admission rate to intensive care (71% vs. 0%; P < 0.001) and a higher risk of death (38% vs. 7%; P = 0.005).CONCLUSION: TB/HS+ occurred more likely in immunocompromised patients and severely impaired the prognosis of TB. Further studies are needed to devise therapeutic strategies for patients with TB/HS+.

Caplacizumab to treat immune-mediated thrombotic thrombocytopenic purpura.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and multiorgan failure, resulting from autoantibody-mediated severe A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) deficiency. In spite of treatment with plasma exchange and immunosuppression, patients remain at risk of exacerbations, refractoriness and death. Caplacizumab (Cablivi; Ablynx, a Sanofi company), a nanobody targeting von Willebrand factor (vWF), has been recently approved in the E.U. and the U.S. as the first therapeutic specifically indicated for the treatment of adults experiencing an episode of iTTP. Caplacizumab blocks the interaction of all multimers with platelets and, therefore, has an immediate effect on platelet aggregation and the ensuing formation and accumulation of platelet-rich microthrombi. This immediate effect of caplacizumab has the potential to protect the patient from tissue ischemia and organ dysfunction while the underlying disease process resolves. We detail here the preclinical and clinical data on caplacizumab for iTTP, including the recent studies that led to approval by the U.S. Food and Drug Administration (FDA) in 2019.

Plasma for direct therapeutic use, for today and tomorrow: A short critical overview.

Plasma for direct therapeutic use is a fast-evolving blood component in terms of its production and presentation. More than a dozen forms are available worldwide, which is often overlooked since most countries apply policies making only one or very few forms available for treating patients in need. It is most often reserved for the same three clinical indications, i.e. overall clotting-factor deficiency, reversal of vitamin K antagonists in the context of active bleeding or prior to urgent surgery, and therapeutic plasma exchange. The level of evidence is often less robust than generally acknowledged for such major indications while novel indications are tending to emerge in medical and trauma settings. This short review explores classical views and new prospects opened up by novel presentations and statuses for therapeutic plasma.

An open conformation of ADAMTS-13 is a hallmark of acute acquired thrombotic thrombocytopenic purpura.

Essentials Conformational changes in ADAMTS-13 are part of its mode-of-action. The murine anti-ADAMTS-13 antibody 1C4 discriminates between folded and open ADAMTS-13. ADAMTS-13 conformation is open in acute acquired thrombotic thrombocytopenic purpura (TTP). Our study forms an important basis to fully elucidate the pathophysiology of TTP. SUMMARY: Background Acquired thrombotic thrombocytopenic purpura (aTTP) is an autoimmune disorder characterized by absent ADAMTS-13 activity and the presence of anti-ADAMTS-13 autoantibodies. Recently, it was shown that ADAMTS-13 adopts a folded or an open conformation. Objectives As conformational changes in self-antigens play a role in the pathophysiology of different autoimmune diseases, we hypothesized that the conformation of ADAMTS-13 changes during acute aTTP. Methods Antibodies recognizing cryptic epitopes in the spacer domain were generated. Next, the conformation of ADAMTS-13 in 40 healthy donors (HDs), 99 aTTP patients (63 in the acute phase versus 36 in remission), 12 hemolytic-uremic syndrome (HUS) patients and 63 sepsis patients was determined with ELISA. Results The antibody 1C4 recognizes a cryptic epitope in ADAMTS-13. Therefore, we were able to discriminate between a folded and an open ADAMTS-13 conformation. We showed that ADAMTS-13 in HDs does not bind to 1C4, indicating that ADAMTS-13 circulates in a folded conformation. Similar results were obtained for HUS and sepsis patients. In contrast, ADAMTS-13 of acute aTTP patients bound to 1C4 in 92% of the cases, whereas, in most cases, this binding was abolished during remission, showing that the conformation of ADAMTS-13 is open during an acute aTTP episode. Conclusions Our study shows that, besides absent ADAMTS-13 activity and the presence of anti-ADAMTS-13 autoantibodies, an open ADAMTS-13 conformation is also a hallmark of acute aTTP. Demonstrating this altered ADAMTS-13 conformation in acute aTTP will help to further unravel the pathophysiology of aTTP and lead to improved therapy and diagnosis.

Amotosalen-inactivated plasma is as equally well tolerated as quarantine plasma in patients undergoing large volume therapeutic plasma exchange.

A retrospective - single center - survey compared tolerance of individual donor therapeutic plasma in a series of 88 patients principally presenting with thrombotic microangiopathy; all patients underwent therapeutic plasma exchange (TPE) performed with more than 90% of either of two types of plasma preparations. One plasma type used in TPE was prepared with pathogen reduction by amotosalen addition and UVA illumination, and the other one was non-manipulated (quarantine plasma). Both types of plasma were single donor. Occurrences of adverse reactions were equally low in either arm (amotosalen: 9 in 4689 bags of ∼200mL [0.019] versus quarantine: 2 in 828 bags [0.024]), confirming the safe use of amotosalen inactivated therapeutic plasma for TPE.

Amplified endogenous plasmin activity resolves acute thrombotic thrombocytopenic purpura in mice.

Essentials Plasmin is able to proteolyse von Willebrand factor. It was unclear if plasmin influences acute thrombotic thrombocytopenic purpura (TTP). Plasmin levels are increased during acute TTP though suppressed via plasmin(ogen) inhibitors. Allowing amplified endogenous plasmin activity in mice results in resolution of TTP signs. SUMMARY: Background Thrombotic thrombocytopenic purpura (TTP) is an acute life-threatening pathology, caused by occlusive von Willebrand factor (VWF)-rich microthrombi that accumulate in the absence of ADAMTS-13. We previously demonstrated that plasmin can cleave VWF and that plasmin is generated in patients during acute TTP. However, the exact role of plasmin in TTP remains unclear. Objectives Investigate if endogenous plasmin-mediated proteolysis of VWF can influence acute TTP episodes. Results In mice with an acquired ADAMTS-13 deficiency, plasmin is generated during TTP as reflected by increased plasmin-α2-antiplasmin (PAP)-complex levels. However, mice still developed TTP, suggesting that this increase is not sufficient to control the pathology. As mice with TTP also had increased plasminogen activator inhibitor 1 (PAI-1) levels, we investigated whether blocking the plasmin(ogen) inhibitors would result in the generation of sufficient plasmin to influence TTP outcome in mice. Interestingly, when amplified plasmin activity was allowed (α2-antiplasmin-/- mice with inhibited PAI-1) in mice with an acquired ADAMTS-13 deficiency, a resolution of TTP signs was observed as a result of an increased proteolysis of VWF. In line with this, in patients with acute TTP, increased PAP-complex and PAI-1 levels were also observed. However, neither PAP-complex levels nor PAI-1 levels were related to TTP signs and outcome. Conclusions In conclusion, endogenous plasmin levels are increased during acute TTP, although limited via suppression through α2-antiplasmin and PAI-1. Only when amplified plasmin activity is allowed, plasmin can function as a back-up for ADAMTS-13 in mice and resolve TTP signs as a result of an increased proteolysis of VWF.

[Hemolytic and uremic syndrome and related thrombotic microangiopathies: Treatment and prognosis]. / Syndromes hémolytiques et urémiques (SHU) et syndromes de microangiopathie thrombotique apparentés : traitement et pronostic.

Major achievements in the understanding of thrombotic microangiopathies (TMA) have not only resulted in a reclassification of TMA but most of all they have culminated in the design of new treatments and have enabled clinicians to better delineate their prognosis. Recent multicenter studies have improved our understanding of the prognosis of atypical hemolytic and uremic syndromes (aHUS). More specifically, they have highlighted the role of genetic testing on predicting the recurrence of aHUS, the risk of chronic kidney disease and the recurrence following kidney transplantation. A major advance consisted of the identification of the alternative complement pathway in the pathogenesis of aHUS, thus paving the way for the use of the C5a inhibitor eculizumab in this indication. Eculizumab has thereafter dramatically improved the management of patients affected with aHUS. During spring 2011, a great epidemic of entero-hemorrhagic Escherichia coli (EHEC) associated HUS occurred in Germany, providing clinicians the opportunity to examine the relevance of antibiotic prophylaxis, plasma exchange and eculizumab in EHEC-associated HUS. In this work, we herein present advances achieved in the setting of therapeutic management and prognosis in HUS and other related TMA syndromes.

[Secondary thrombotic microangiopathies]. / Microangiopathies thrombotiques secondaires.

Thrombotic microangiopathies (TMA) are termed secondary when associated to a specific context favouring their occurrence. They encompass mainly TMA associated with pregnancy, allogeneic hematopoietic stem cell transplantation, cancer, drugs, or HIV infection. Secondary TMA represent a heterogeneous group of diseases which clinical presentation largely depends on the associated context. It is therefore mandatory to recognize these conditions since they have a significant impact in TMA management and prognosis. A successful management still represents a challenge in secondary TMA. Significant progresses have been made in the understanding of pregnancy-associated TMA, allowing an improvement of prognosis; on the opposite, other forms of secondary TMA such as hematopoietic stem cell transplantation-associated TMA or TMA associated with chemotherapy remain of dismal prognosis. A better understanding of pathophysiology in these forms of TMA, in association with a more empirical approach through the use of new therapeutic agents that can also help in the understanding on new mechanisms a posteriori, should improve their prognosis. The preliminary encouraging results reported with complement blockers in this field could represent a convincing example.

[Hemolytic and uremic syndrome and related thrombotic microangiopathies: Epidemiology, pathophysiology and clinics]. / SHU et syndromes de microangiopathie thrombotique apparentés : épidémiologie, physiopathologie et tableaux cliniques.

Thrombotic microangiopathies (TMA) represent an eclectic group of conditions, which share hemolytic anemia and thrombocytopenia as a common defining basis. Remarkable breakthroughs in the physiopathological setting have allowed for a thorough recomposition of the disparate syndromes, which form the constellation of TMA. In this view, clinicians now discriminate thrombocytopenic thrombotic purpura (TTP) defined by a severe deficiency in ADAMTS13, which is rarely associated with a severe renal involvement and the hemolytic and uremic syndrome (HUS) in which renal impairment is the most prominent clinical feature. HUS can result from toxins stemming from bacterial infections of the digestive tract, alternate complement pathway abnormalities, metabolic or coagulation disorders or, lastly, drug and various toxic compounds. The diverse forms of HUS reflect the insights gained in the understanding of the pathophysiological mechanisms underpinning TMA. In this first part, a broad overview of the epidemiological, physiopathological and clinical aspects of HUS and related TMA syndromes is presented.

Management of thrombotic thrombocytopenic purpura.

Daily therapeutic plasma exchange (TPE) transformed the historically fatal prognosis of acquired, anti-ADAMTS13 antibody-mediated thrombotic thrombocytopenic purpura (TTP), leading to the current overall survival rates of >80%. However, relapses occur in up to 40% of patients and refractory disease with fatal outcomes still occurs, typically within the first days of management. In this context, the introduction of rituximab has been the second major breakthrough in TTP management. Rituximab is now routinely recommended during the acute phase, typically in patients with a suboptimal response to treatment, and increasingly as frontline therapy, with high response rates in the following weeks. In more severe patients, salvage strategies typically include twice daily TPE, pulses of cyclophosphamide, as well as splenectomy in the more desperate cases. In this life-threatening and debilitating disease, relapses can be efficiently prevented in patients with a severe acquired ADAMTS13 deficiency and otherwise in remission with the use of rituximab. In the coming years, the TTP therapeutic landscape should be enriched by original strategies stemming from clinical experience and new agents that are currently being evaluated in large, international, clinical trials. Promising agents under evaluation include caplacizumab (an inhibitor of the glycoprotein-Ib/IX-Von-Willebrand factor axis), N-acetylcysteine, recombinant ADAMTS13, and anti-plasmocyte compounds.

Clinical characteristics and prognostic factors of plasmablastic lymphoma patients: analysis of 135 patients from the LYSA group.

Background: Plasmablastic lymphoma (PBL), initially described in 1997 in the oral cavity of HIV positive patients, is now recognized as a distinct aggressive and rare entity of diffuse large B-cells lymphoma by the World Health Organization (WHO) classification. Since the original description, others cases have been reported. However, these are largely derived from case reports or small series limiting any definitive conclusions on clinical characteristics and outcome. Patients and methods: The clinical, biological, pathological features and outcome of a cohort including 135 patients with PBL, from LYSA centers in France and Belgium, were reported and analyzed. Results: The median age was 58 years, with a male predominance. The cohort was divided into 56 HIV-positive patients, 17 post-transplant patients and 62 HIV-negative/non-transplanted patients. Within HIV-negative/non-transplanted, a relative immunosuppression was found in most cases (systemic inflammatory disease, history of cancer, increased age associated with weakened immune system). We have also described a new subtype, PBL arising in a chronic localized inflammatory site, without any sign of immunosuppression. At presentation, 19% of patients showed oral involvement. Immunophenotype showed CD138 positivity in 88% of cases and CD20 negativity in 90% of cases. Chemotherapy was administered to 80% of patients, with a complete response (CR) rate of 55%. The median overall survival (OS) was 32 months. In univariate analysis, HIV positive status showed better OS when compared with HIV negative status. In multivariate analysis, International Prognostic Index score, chemotherapy and CR were associated with survival benefit. Conclusion(s): This cohort, the largest reported to date, increases the spectrum of knowledge on PBL, rarely described. However, specific guidelines to clarify treatment are lacking, and may improve the poor prognosis of this rare disease.

[Autoimmune and inflammatory disorders associated with lymphoid hematological malignancies]. / Manifestations auto-immunes et inflammatoires des hémopathies lymphoïdes.

In this literature review, we reported autoimmune and inflammatory disorders associated with lymphoid hematological malignancies, including non-Hodgkin's lymphoma, Hodgkin's lymphoma and chronic lymphocytic leukemia. The different types of systemic involvement are classified by affected organ. We listed in this review the joint diseases, skin, neurologic, hematologic, renal, and vasculitis. We tried to determine whether there is a correlation between each autoimmune manifestation and a specific type of lymphoma or a particular feature that may support a paraneoplastic origin, if there is an impact on the prognosis of the hematological malignancy, and finally, we identified the different therapeutic strategies used in the literature.

Consensus on the standardization of terminology in thrombotic thrombocytopenic purpura and related thrombotic microangiopathies.

Essentials An international collaboration provides a consensus for clinical definitions. This concerns thrombotic microangiopathies and thrombotic thrombocytopenic purpura (TTP). The consensus defines diagnosis, disease monitoring and response to treatment. Requirements for ADAMTS-13 are given. SUMMARY: Background Thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS) are two important acute conditions to diagnose. Thrombotic microangiopathy (TMA) is a broad pathophysiologic process that leads to microangiopathic hemolytic anemia and thrombocytopenia, and involves capillary and small-vessel platelet aggregates. The most common cause is disseminated intravascular coagulation, which may be differentiated by abnormal coagulation. Clinically, a number of conditions present with microangiopathic hemolytic anemia and thrombocytopenia, including cancer, infection, transplantation, drug use, autoimmune disease, and pre-eclampsia and hemolysis, elevated liver enzymes and low platelet count syndrome in pregnancy. Despite overlapping clinical presentations, TTP and HUS have distinct pathophysiologies and treatment pathways. Objectives To present a consensus document from an International Working Group on TTP and associated thrombotic microangiopathies (TMAs). Methods The International Working Group has proposed definitions and terminology based on published information and consensus-based recommendations. Conclusion The consensus aims to aid clinical decisions, but also future studies and trials, utilizing standardized definitions. It presents a classification of the causes of TMA, and criteria for clinical response, remission and relapse of congenital and immune-mediated TTP.

Assessment of endothelial damage and cardiac injury in a mouse model mimicking thrombotic thrombocytopenic purpura.

Essentials Endothelial injury is thought to be a key event in thrombotic thrombocytopenic purpura (TTP). Endothelial and cardiac damages were assessed in a model of TTP using ADAMTS-13 knockout mice. Damages of cardiac perfusion and function were associated with nitric oxide pathway alteration. Endothelial dysfunction constitutes a critical event in TTP development and cardiac injury. SUMMARY: Background Cardiac alterations represent a major cause of mortality in patients with thrombotic thrombocytopenic purpura (TTP). Endothelial injury remains poorly defined, but seems to be a key initiating event leading to the formation of platelet-rich thrombi in TTP patients. Objectives To assess the changes in endothelial function and the induced cardiac damage in a mouse model of TTP. Patients/methods We used an animal model in which TTP-like symptoms are triggered by injection of 2000 units kg-1 of recombinant von Willebrand factor in ADAMTS-13 knockout mice. Results These mice developed TTP-like symptoms, i.e. severe thrombocytopenia, schistocytosis, and anemia. On day 2, magnetic resonance imaging demonstrated a decrease in left ventricular perfusion associated with alteration of left ventricular ejection fraction, fractional shortening, and cardiac output, suggesting early systolic dysfunction. This was associated with decrease in endothelium-mediated relaxation responses to acetylcholine in mesenteric and coronary arteries, demonstrating severe early endothelial dysfunction. In parallel, we showed decreased cardiac expression of endothelial nitric oxide (NO) synthase and increased expression of antioxidant enzymes, suggesting alteration of the NO pathway. At this time, cardiac immunohistochemistry revealed an increase in the expression of VCAM-1 and E-selectin. Conclusion This study provides evidence that the heart is a sensitive target organ in TTP, and shows, for the first time, strong mesenteric and coronary endothelial dysfunction in an induced-TTP model. The mechanisms incriminated are the occurrence of a pro-oxidant state, and proadhesive and proinflammatory phenotypes. This previously largely unrecognized vascular dysfunction may represent an important contributor to the systemic organ failure occurring in TTP.