Evaluation and Management of Patients With Thrombotic Thrombocytopenic Purpura

Deletion of platelet CLEC-2 decreases GPIbα-mediated integrin αIIbβ3 activation and decreases thrombosis in TTP

Microvascular thrombosis in patients with thrombotic thrombocytopenic purpura (TTP) is initiated by GPIbα-mediated platelet binding to von Willebrand factor (VWF). Binding of VWF to GPIbα causes activation of the platelet surface integrin αIIbβ3. However, the mechanism of GPIbα-initiated activation of αIIbβ3 and its clinical importance for microvascular thrombosis remain elusive. Deletion of platelet C-type lectin-like receptor 2 (CLEC-2) did not prevent VWF binding to platelets but specifically inhibited platelet aggregation induced by VWF binding in mice. Deletion of platelet CLEC-2 also inhibited αIIbβ3 activation induced by the binding of VWF to GPIbα. Using a mouse model of TTP, which was created by infusion of anti-mouse ADAMTS13 monoclonal antibodies followed by infusion of VWF, we found that deletion of platelet CLEC-2 decreased pulmonary arterial thrombosis and the severity of thrombocytopenia. Importantly, prophylactic oral administration of aspirin, an inhibitor of platelet activation, and therapeutic treatment of the TTP mice with eptifibatide, an integrin αIIbβ3 antagonist, reduced pulmonary arterial thrombosis in the TTP mouse model. Our observations demonstrate that GPIbα-mediated activation of integrin αIIbβ3 plays an important role in the formation of thrombosis in TTP. These observations suggest that prevention of platelet activation with aspirin may reduce the risk for thrombosis in patients with TTP.

A critical evaluation of caplacizumab for the treatment of acquired thrombotic thrombocytopenic purpura

Introduction: Acquired thrombotic thrombocytopenic purpura (aTTP) is a thrombotic microangiopathy caused by inhibitory autoantibodies against ADAMTS13 protein. Until recently, the combination of plasma exchange (PEX) and immunosuppression has been the standard front-line treatment in this disorder. However, aTTP-related mortality, refractoriness, and relapse are still a matter of concern. Areas covered: The better understanding of the pathophysiological mechanisms of aTTP has allowed substantial improvements in the diagnosis and treatment of this disease. Recently, the novel anti-VWF nanobody caplacizumab has been approved for acute episodes of aTTP. Caplacizumab is capable to block the adhesion of platelets to VWF, therefore inhibiting microthrombi formation in the ADAMTS13-deficient circulation. In this review, the characteristics of caplacizumab together with the available data of its efficacy and safety in the clinical setting will be analyzed. Besides, the current scenario of aTTP treatment will be provided, including the role of other innovative drugs. Expert opinion: With no doubt, caplacizumab is going to change the way we treat aTTP. In combination with standard treatment, caplacizumab can help to significantly reduce aTTP-related mortality and morbidity and could spare potential long-term consequences by minimizing the risk of exacerbation.

Nonsteroidal Anti-inflammatory Drug Induced Thrombotic Thrombocytopenic Purpura

A 21-year-old male presented to the emergency department after a 5-day history of recurrent vomiting and decreased urine output. History revealed ingestion of ibuprofen. During the diagnostic workup, the following was identified: white blood cell count 13.4 (×10(3)/mcL), hemoglobin 11.9 (×10(6)/mcL) with an MCV of 73 fL, hematocrit 34% and platelets were 31,000/mcL, sodium of 130 mmol/L, potassium of 5.1 mmol/L, chloride of 83 mmol/L, bicarbonate of 21 mmol/L, blood urea nitrogen of 184 mg/dL and creatinine of 19.1 mg/dL. He was later diagnosed with thrombotic thrombocytopenic purpura (TTP) based on the fact that he presented with most components of the TTP pentad (except for fever), which included altered mental status, acute kidney injury, thrombocytopenia, and evidence of red cell fragmentation and his ADAMTS13 level was found to be less than 10% prior to therapy. The patient then received plasma exchange, oral corticosteroids, and hemodialysis, which led to a full recovery of platelet count and renal function.

Fever and neurologic conditions

Neurologic conditions are categorized as either those that cause a change in mental status or those that create a focal finding on physical examination. Neurologic abnormality associated with fever can be caused by a primary neurologic condition or one that does not originate in the central nervous system. Optimal management of such conditions requires high clinical suspicion and a broad differential diagnosis, which facilitates rapid recognition and effective treatment. A thorough history and physical examination are key determinants in accurately diagnosing neurologic conditions associated with fever, often requiring acquisition of collateral information from persons other than the patient.

Recurrent thrombotic thrombocytopenic purpura-like syndrome as a paraneoplastic phenomenon in malignant peritoneal mesothelioma: a case report and review of the literature

We report the case of an African American male with no significant past medical history presenting with recurrent, rapidly relapsing episodes of thrombotic thrombocytopenic purpura (TTP) despite aggressive treatment with several lines of treatment. Incidentally, these episodes were associated with severe abdominal pain which eventually developed into acute abdomen and prompted exploratory laparotomy, revealing diffuse carcinomatosis with a tumor located on the left pelvis that was encasing the distal sigmoid colon. Pathology made a final diagnosis of peritoneal mesothelioma. TTP-like syndrome (TTP-LS) has been described as a paraneoplastic phenomenon in several malignancies but never before in the setting of malignant mesothelioma. Paraneoplastic TTP-like syndrome has historically been associated with a dismal prognosis and particular clinical and laboratory abnormalities described in this paper. It is of utmost importance to make a prompt determination whether TTP is idiopathic or secondary to an underlying condition because of significant differences in their prognosis, treatment, and response. This paper also reviews the current literature regarding this challenging condition.

Evaluation of efficacy and safety of the anti-VWF Nanobody ALX-0681 in a preclinical baboon model of acquired thrombotic thrombocytopenic purpura

ALX-0681 is a therapeutic Nanobody targeting the A1-domain of VWF. It inhibits the interaction between ultra-large VWF and platelet GpIb-IX-V, which plays a crucial role in the pathogenesis of thrombotic thrombocytopenic purpura (TTP). In the present study, we report the efficacy and safety profile of ALX-0681 in a baboon model of acquired TTP. In this model, acute episodes of TTP are induced by administration of an ADAMTS13-inhibiting mAb. ALX-0681 completely prevented the rapid onset of severe thrombocytopenia and schistocytic hemolytic anemia. After induction of TTP, platelet counts also rapidly recovered on administration of ALX-0681. This effect was corroborated by the full neutralization of VWF activity. The schistocytic hemolytic anemia was also halted and partially reversed by ALX-0681 treatment. Brain CT scans and post mortem analysis did not reveal any sign of bleeding, suggesting that complete neutralization of VWF by ALX-0681 under conditions of thrombocytopenia was not linked with an excessive bleeding risk. The results obtained in this study demonstrate that ALX-0681 can successfully treat and prevent the most important hallmarks of acquired TTP without evidence of a severe bleeding risk. Therefore, ALX-0681 offers an attractive new therapeutic option for acquired TTP in the clinical setting.

The TITAN trial--assessing the efficacy and safety of an anti-von Willebrand factor Nanobody in patients with acquired thrombotic thrombocytopenic purpura

The Phase II TITAN trial is designed to assess the efficacy and safety of an anti-von Willebrand factor (vWF) Nanobody in patients with acquired thrombotic thrombocytopenic purpura (TTP). Nanobodies are a novel class of therapeutic proteins and are based on the smallest functional fragments of single-chain antibodies that occur naturally in the Camelidae family (Nanobody® and Nanobodies® are registered trademarks of Ablynx NV). With vWF implicated in the thrombotic process underlying TTP, an anti-vWF Nanobody may hold significant promise as adjunctive therapy to plasma exchange. Recruitment is currently ongoing, and aims to include a total of 110 patients from countries in Europe, the Middle East, Australia and Northern America.

Thrombotic thrombocytopenic purpura at the Johns Hopkins Hospital from 1992 to 2008: clinical outcomes and risk factors for relapse

BACKGROUND

Plasma exchange, the standard treatment for thrombotic thrombocytopenic purpura (TTP), has significantly decreased disease mortality. However, TTP recurs in 20% to 50% of patients who survive the initial episode. We aimed to describe the clinical spectrum of TTP, to determine the valid endpoint for plasma exchange cessation, and to explore the risk factors for disease relapse.

STUDY DESIGN AND METHODS

Using the ICD-9 diagnosis code, we identified patients treated for TTP at the Johns Hopkins Hospital between 1992 and 2008. Complete demographic, clinical, laboratory, treatment, and outcome data were collected from the medical records.

RESULTS

A total of 72 patients were treated for 134 episodes of TTP at the Johns Hopkins Hospital during the study period. With standardized combined immunosuppression and plasma exchange treatment, the all-cause mortality rate was 4%. Lactate dehydrogenase (LDH) normalization lagged behind platelet (PLT) recovery by an average of 9 days and did not predict response. Relapse occurred in 36% of patients during a median follow-up of 30 months with most (76%) occurring in the first 24 months. African American ethnicity was associated with increased risk of relapse (odds ratio = 4.8, p = 0.03).

CONCLUSIONS

Excellent outcomes in patients with TTP are achievable with multimodality therapy. LDH normalization lags behind PLT recovery and might not be an informative endpoint for plasma exchange cessation. Prospective studies are warranted to confirm the influence of race on relapse and identify additional risk factors for adverse outcomes that could be targeted to improve therapeutic outcomes for patients with TTP.

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.

Coagulation disorders in the ICU

Disorders of hemostasis and thrombosis are frequently encountered in the ICU setting. Understanding the relevance of laboratory findings is essential in providing appropriate therapy. Various blood products and hemostatic agents are available to assist in the control of bleeding, and several different classes of anticoagulants are now available for use. Appropriate use of these agents maximizes therapeutic effect while minimizing complications. Use of fresh frozen plasma, cryoprecipitate, and other hemostatic agents should generally be reserved for those who have active bleeding, those undergoing invasive procedures, and those at high risk for bleeding because of their underlying diagnoses or because of associated hematologic derangements.

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.