Specific von Willebrand factor-cleaving protease in thrombotic microangiopathies: a study of 111 cases

Management and follow-up of pregnancy-onset thrombotic thrombocytopenic purpura: the French experience

ABSTRACT

Pregnancy-onset thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening disease of which diagnosis and management requires experienced multidisciplinary teams. The mechanisms responsible for a deficiency in the disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13 (ADAMTS13) leading to pregnancy-onset TTP may be congenital or acquired, and studying ADAMTS13 conformation could be of interest. The differential diagnosis between TTP and other pregnancy-associated thrombotic microangiopathies (TMA) is often challenging. Our retrospective multicenter study highlights the significance and the challenges associated with pregnancy-onset TTP and childbirth in terms of diagnosis, obstetric management, and follow-up aspects. Among 1174 pregnancy-onset TMA enrolled in the French Registry for TMA from 2000 to 2020, we identified 108 pregnancy-onset TTP: 52 immune-mediated TTP (iTTP, 48.1%), 27 acquired TTP of unidentified mechanism (uTTP, 25%), and 29 congenital TTP (cTTP, 26.9%). Data show that maternal outcome is good (survival rate: 95%) and fetal outcome is linked to the gestational age at the onset of the disease (survival rate: 75.5%). Three distinct entities with different natural histories emerged: pregnancy-onset iTTP appears similar to idiopathic iTTP, with an open ADAMTS13 conformation, and is marked by a relapse risk independent of subsequent pregnancies; pregnancy-onset uTTP appears to have a different pathophysiology with an unexpected open ADAMTS13 conformation and a very low relapse risk independent of subsequent pregnancies; finally, pregnancy-onset cTTP is characterized by the necessity of pregnancy as a systematic and specific trigger and a need for prophylactic plasmatherapy for subsequent pregnancies. This trial was registered at www.clinicaltrials.gov as #NCT00426686, and at the Health Authority and the French Ministry of Health (P051064/PHRC AOM05012).

Clinical characteristics, treatments, and outcomes of interferon-beta-induced thrombotic microangiopathy: a literature-based retrospective analysis

Background

Thrombotic microangiopathy (TMA) is a rare side effect of interferon-beta (IFN-β) therapy. The clinical characteristics of IFN-β-induced TMA are unknown.

Objectives

To explore the clinical characteristics of IFN-β-induced TMA and provide reference for the prevention of TMA.

Design

Articles on IFN-β-induced TMA were collected by searching the literature in relevant Chinese and English databases from inception to 31 July 2023.

Methods

Data in the articles were extracted and analyzed retrospectively.

Results

Forty-seven patients, with a median age of 41 years (range 22, 66), were included in the analysis. The median time to the diagnosis of IFN-β-induced TMA was 8 years (range 0.1-30) after administration. The main clinical symptoms were neurological symptoms (51.1%), hypertension (78.7%), dyspnea (19.1%), edema (19.1%), asthenia/fatigue (19.1%), and digestive symptoms (17.0%). Most patients presented with hemolytic anemia (76.6%), thrombocytopenia (63.8%), and acute kidney injury (70.2%). All patients stopped IFN-β and received plasma exchange therapy (53.2%), systemic steroids (46.8%), antihypertensive therapy (46.8%), eculizumab (12.8%), and rituximab (12.8%). Kidney damage was not completely reversible; 40.4% of patients achieved renal function and hematology remission, 27.7% developed chronic kidney disease, 25.5% developed end-stage renal disease, and 2.1% died.

Conclusion

IFN-β-induced TMA is a rare but serious complication that can be life-threatening. It may occur after many years of IFN-β therapy, and patients taking IFN-β should be monitored for symptoms such as headache and hypertension.

Cattle-FRETS71, a novel fluorogenic substrate with broad applicability for characterizing ADAMTS13 properties and function

BACKGROUND

Current ADAMTS13 activity assays are important for diagnosing thrombotic thrombocytopenic purpura (TTP) but are unreliable to assay ADAMTS13 activity in animal models. The Cattle-FRETS71 assay is capable of detecting ADAMTS13 activity in plasma from multiple animal species, making it a potentially useful reagent at all stages of clinical research. The performance of Cattle-FRETS71 in TTP diagnosis is not yet known.

OBJECTIVES

We evaluated the performance of the Cattle-FRETS71 substrate against the human FRETS-rVWF71 and the FRETS-VWF73 commercial substrates in human plasma and serum samples to validate its utility in diagnosing TTP in patients.

METHODS

Internal validation was performed using heparinized plasma samples (n = 81). External validation was a blinded study using serum samples from the Oklahoma TTP Registry (n = 118, collected 2004-2014) that had been initially assayed by FRETS-VWF73 within 1 year of collection. Additional validation was performed with citrated plasma samples with variable ADAMTS13 activities (n = 32) that were analyzed by FRETS-VWF73.

RESULTS

There was an excellent correlation (r = 0.94) between Cattle-FRETS71 and FRETS-rVWF71 for assayed heparinized plasma samples (n = 81). Assay results between Cattle-FRETS71 and FRETS-VWF73 of Oklahoma TTP Registry serum samples (n = 118) and citrated plasma samples (n = 32) were comparably good (r = 0.81 and r = 0.85, respectively).

CONCLUSION

The Cattle-FRETS71 assay is comparable with other assays in quantifying ADAMTS13 activity in human plasma collected from patients with documented or suspected TTP. The versatility of Cattle-FRETS71, combined with its specificity and sensitivity, makes it a useful tool for the standardization of ADAMTS13 activity across basic and clinical research paradigms.

ADAMTS13 and Non-ADAMTS13 Biomarkers in Immune-Mediated Thrombotic Thrombocytopenic Purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare medical emergency for which a correct and early diagnosis is essential. As a severe deficiency in A Disintegrin And Metalloproteinase with ThromboSpondin type 1 repeats, member 13 (ADAMTS13) is the underlying pathophysiology, diagnostic strategies require timely monitoring of ADAMTS13 parameters to differentiate TTP from alternative thrombotic microangiopathies (TMAs) and to guide initial patient management. Assays for conventional ADAMTS13 testing focus on the enzyme activity and presence of (inhibitory) anti-ADAMTS13 antibodies to discriminate immune-mediated TTP (iTTP) from congenital TTP and guide patient management. However, diagnosis of iTTP remains challenging when patients present borderline ADAMTS13 activity. Therefore, additional biomarkers would be helpful to support correct clinical judgment. Over the last few years, the evaluation of ADAMTS13 conformation has proven to be a valuable tool to confirm the diagnosis of acute iTTP when ADAMST13 activity is between 10 and 20%. Screening of ADAMTS13 conformation during long-term patient follow-up suggests it is a surrogate marker for undetectable antibodies. Moreover, some non-ADAMTS13 parameters gained notable interest in predicting disease outcome, proposing meticulous follow-up of iTTP patients. This review summarizes non-ADAMTS13 biomarkers for which inclusion in routine clinical testing could largely benefit differential diagnosis and follow-up of iTTP patients.

A novel von Willebrand factor multimer ratio as marker of disease activity in thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP), an autoantibody-mediated severe ADAMTS13 deficiency, is caused by insufficient proteolytic processing of von Willebrand factor (VWF) multimers (MMs) and microvascular thrombi. Recurrence of acute iTTP is associated with persistence or reappearance of ADAMTS13 deficiency. Some patients remain in remission despite recurring or persisting severe ADAMTS13 deficiency. In a prospective 2-year observational study, we investigated VWF MM patterns and ADAMTS13 in patients with iTTP in remission and at acute episodes. Of the 83 patients with iTTP, 16 suffered 22 acute episodes whereas 67 remained in clinical remission during follow-up, including 13 with ADAMTS13 <10% and 54 with ADAMTS13 ≥10%. High -molecular weight to low-molecular weight VWF MM ratio based on sodium dodecyl sulfate-agarose gel electrophoresis was compared with ADAMTS13 activity. VWF MM ratio was significantly higher in patients in remission with <10% compared with ≥10% ADAMTS13 activity. Fourteen samples obtained from 13 to 50 days (interquartile range; median, 39) before acute iTTP onset (ADAMTS13 <10% in 9 patients and 10%-26% in 5) showed VWF MM ratios significantly higher than those from 13 patients remaining in remission with ADAMTS13 <10%. At acute iTTP onset, VWF MM ratio decreased significantly and was low in all patients despite <10% ADAMTS13. The VWF MM ratio does not depend exclusively on ADAMTS13 activity. The disappearance of high molecular weight VWF MMs resulting in low VWF MM ratio at iTTP onset may be explained by consumption of larger VWF MMs in the microcirculation. The very high VWF MM ratio preceding acute iTTP recurrence suggests that VWF processing is hampered more than in patients remaining in remission.

Anti-ADAMTS13 Autoantibodies: From Pathophysiology to Prognostic Impact-A Review for Clinicians

Thrombotic thrombocytopenic purpura (TTP) is a fatal disease in which platelet-rich microthrombi cause end-organ ischemia and damage. TTP is caused by markedly reduced ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity. ADAMTS13 autoantibodies (autoAbs) are the major cause of immune TTP (iTTP), determining ADAMTS13 deficiency. The pathophysiology of such autoAbs as well as their prognostic role are continuous objects of scientific studies in iTTP fields. This review aims to provide clinicians with the basic information and updates on autoAbs' structure and function, how they are typically detected in the laboratory and their prognostic implications. This information could be useful in clinical practice and contribute to future research implementations on this specific topic.

Molecular Diagnosis Is Vital to the Accurate Classification and Management of Thrombotic Thrombocytopenic Purpura in Children

Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially life-threatening hematologic disease, presenting a myriad of diagnostic and management challenges in children. Here, we provide a review of this disorder and discuss 2 exemplary cases of TTP occurring in adolescents, emphasizing the need for consideration of late-onset congenital TTP (cTTP). We demonstrate the importance of early confirmation of ADAMTS13 enzyme deficiency and the presence or absence of ADAMTS13 inhibitor in order to rapidly initiate the appropriate life-saving therapies. Ultimately, molecular testing is paramount to distinguishing between congenital and acquired immune-mediated TTP.

Bioprosthetic Total Artificial Heart in Autoregulated Mode Is Biologically Hemocompatible: Insights for Multimers of von Willebrand Factor

BACKGROUND

Carmat bioprosthetic total artificial heart (Aeson; A-TAH) is a pulsatile and autoregulated device. The aim of this study is to evaluate level of hemolysis potential acquired von Willebrand syndrome after A-TAH implantation.

METHODS

We examined the presence of hemolysis and acquired von Willebrand syndrome in adult patients receiving A-TAH support (n=10) during their whole clinical follow-up in comparison with control subjects and adult patients receiving Heartmate II or Heartmate III support. We also performed a fluid structure interaction model coupled with computational fluid dynamics simulation to evaluate the A-TAH resulting shear stress and its distribution in the blood volume.

RESULTS

The cumulative duration of A-TAH support was 2087 days. A-TAH implantation did not affect plasma free hemoglobin over time, and there was no association between plasma free hemoglobin and cardiac output or beat rate. For VWF (von Willebrand factor) evaluation, A-TAH implantation did not modify multimers profile of VWF in contrast to Heartmate II and Heartmate III. Furthermore, fluid structure interaction coupled with computational fluid dynamics showed a gradually increase of blood damage according to increase of cardiac output (P<0.01), however, the blood volume fraction that endured significant shear stresses was always inferior to 0.03% of the volume for both ventricles in all regimens tested. An inverse association between cardiac output, beat rate, and high-molecular weight multimers ratio was found.

CONCLUSIONS

We demonstrated that A-TAH does not cause hemolysis or AWVS. However, relationship between HMWM and cardiac output depending flow confirms relevance of VWF as a biological sensor of blood flow, even in normal range.

Severe Thrombotic Thrombocytopenic Purpura (TTP) with Organ Failure in Critically Ill Patients

Thrombotic thrombocytopenic purpura (TTP) is a multiorgan disorder. Organ dysfunction occurs as a consequence of widespread microvascular thrombosis, especially in the heart, brain and kidney, causing transient or partial occlusion of vessels, resulting in organ ischemia. Intensive care unit (ICU) admission varies between 40% and 100% of patients with TTP, either because of severe organ failure or in order to initiate emergency plasma exchange (PEx). Severe neurologic manifestations and cardiac involvement have been associated with higher mortality. Acute kidney injury, although usually less severe than that in hemolytic and uremic syndrome, is common during TTP. Initial management in the ICU should always be considered in TTP patients. The current treatment of TTP in the acute phase is based on urgent PEx, combined with corticosteroid therapy, B-cell-targeted immunotherapy, rituximab and inhibition of the interaction between ultra-large Von Willebrand factor multimers and platelets, using caplacizumab, a monoclonal antibody. ICU management permits close monitoring and the rapid introduction of life-sustaining therapies. This review details the epidemiology of TTP in the ICU, organ failures of critically ill patients with TTP, and the initial management of TTP patients in the ICU.

Renal diseases and the role of complement: Linking complement to immune effector pathways and therapeutics

The complement system is an ancient and phylogenetically conserved key danger sensing system that is critical for host defense against pathogens. Activation of the complement system is a vital component of innate immunity required for the detection and removal of pathogens. It is also a central orchestrator of adaptive immune responses and a constituent of normal tissue homeostasis. Once complement activation occurs, this system deposits indiscriminately on any cell surface in the vicinity and has the potential to cause unwanted and excessive tissue injury. Deposition of complement components is recognized as a hallmark of a variety of kidney diseases, where it is indeed associated with damage to the self. The provenance and the pathophysiological role(s) played by complement in each kidney disease is not fully understood. However, in recent years there has been a renaissance in the study of complement, with greater appreciation of its intracellular roles as a cell-intrinsic system and its interplay with immune effector pathways. This has been paired with a profusion of novel therapeutic agents antagonizing complement components, including approved inhibitors against complement components (C)1, C3, C5 and C5aR1. A number of clinical trials have investigated the use of these more targeted approaches for the management of kidney diseases. In this review we present and summarize the evidence for the roles of complement in kidney diseases and discuss the available clinical evidence for complement inhibition.

Outcomes in 1096 patients with severe thrombotic thrombocytopenic purpura before the Caplacizumab era

INTRODUCTION

Thrombotic thrombocytopenic purpura (TTP) is a diagnostic and therapeutic emergency. Therapeutic plasma exchange (TPE) combined with immunosuppression has been the cornerstone of the initial management. To produce optimal benefits, emerging treatments must be used against a background of best standard of care. Clarifying current uncertainties is therefore crucial.

METHODS

The objective of this study was to analyze a large high-quality database (Marketscan) of TTP patients managed between 2005 and 2014, in the pre-caplacizumab era, in order to assess the impact of time to first TPE and use of first-line rituximab on mortality, and whether mortality declines over time.

RESULTS

Among the 1096 included patients (median age 46 [IQR 35-55], 70% female), 28.8% received TPE before day 2 in the ICU. Hospital mortality was 7.6% (83 deaths). Mortality was independently associated with older age (hazard ratio [HR], 1.024/year; 95% confidence interval [95%CI], [1.009-1.040]), diagnosis of sepsis (HR, 2.360; 95%CI [1.552-3.588]), and the need for mechanical ventilation (HR, 4.103; 95%CI, [2.749-6.126]). Factors independently associated with lower mortality were TPE at ICU admission (HR, 0.284; 95%CI, [0.112-0.717]), TPE within one day after ICU admission (HR, 0.449; 95%CI, [0.275-0.907]), and early rituximab therapy (HR, 0.229; 95% CI, [0.111-0.471]). Delayed TPE was associated with significantly higher costs.

CONCLUSIONS

Immediate TPE and early rituximab are associated with improved survival in TTP patients. Improved treatments have led to a decline in mortality over time, and alternate outcome variables such as the use of hospital resources or longer term outcomes therefore need to be considered.

Pattern of Brain Injury in Patients With Thrombotic Thrombocytopenic Purpura in the Precaplacizumab Era

OBJECTIVES

To describe short- and long-term neurologic prognosis of patients with thrombotic thrombocytopenic purpura and to identify clusters associated with evolution.

DESIGN

Prospective French cohort.

SETTING

ICU in a reference center.

PATIENTS

All consecutive patients with newly diagnosed thrombocytopenic purpura.

INTERVENTION

Comprehensive clinical, biological, and radiological evaluation at admission. Neurocognitive recovery was assessed using Glasgow Outcome Scale (range 1-5, with 1 representing death and 5 representing no or minimal neurologic deficit).

MEASUREMENTS AND MAIN RESULTS

Among the 130 newly diagnosed patients with thrombocytopenic purpura, 108 (83%; age 43 [30-52]; 73% women) presented with neurologic signs, including headaches (51%), limb weakness, paresthesia, and/or aphasia (49%), pyramidal syndrome (30%), decreased consciousness (20%), seizure (19%), cognitive impairment (34%), cerebellar syndrome (18%), and visual symptoms (20%). A hierarchical cluster analysis identified three distinct groups of patients. Cluster 1 included younger patients (37 [27-48], 41 [32-52], and 48 [35-54], in clusters 1, 2 and 3, respectively; p = 0.045), with a predominance of headaches (75%, 27%, and 36%; p < 0.0001). Cluster 2 patients had ataxic gait and cerebellar syndrome (77%, 0%, and 0%; p < 0.0001) and dizziness (50%, 0%, and 0%; p < 0.0001). Cluster 3 included patients with delirium (36%, 0%, and 9%; p < 0.0001), obtundation (58%, 0%, and 24%; p < 0.0001), and seizure (36%, 0%, and 14%; p < 0.0001). Acute kidney injury was 32%, 68%, and 77%, in clusters 1, 2, and 3, respectively (p < 0.0001). The three clusters did not differ for other biological or brain imaging. After a median follow-up of 34 months (12-71 mo), 100 patients (93%) were alive with full neurocognitive recovery (i.e., Glasgow Outcome Scale score 5) in 89 patients (89%). Patients from cluster 1 more frequently exhibited full recovery (Glasgow Outcome Scale score of 5) compared with clusters 2 and 3, (44 [98%], 13 [65%], and 21 [60%] at 3 mo; p < 0.0001), (44 [100%], 15 [68%], and 23 [69%] at 6 mo; p < 0.0001), and (40 [100%], 15 [79%], and 20 [57%] at 1 yr; p < 0.0001).

CONCLUSIONS

Initial clinical neurologic evaluation in thrombocytopenic purpura patients distinguishes three groups of patients with different clinical and functional outcomes.

[Breast cancer-related thrombotic microangiopathy: A review]

Thrombotic Microangiopathies (TM) have been described since the 1960s. They are characterized by presence of mechanical haemolytic anemia associated with peripheral thrombocytopenia. TM in cancer can be related to several causes, whose cancer himself: cancer-related microangiopathic haemolytic anaemia (MAHA). Incidence of cancer related MAHA remains unknown. Cancer-related MAHA are mainly observed in mucin-producer adenocarcinomas, such as gastric (half of reported cases) and breast cancer. We conducted a review of all original published cases of TM reported in breast cancer, and we specifically investigated BC-MAHA cases. A Medline search identified 158 MAHA cases including 118 BC-MAHA, and 40 drug-related MAHA. Most of BC-MAHA occur in disseminated cancers, mainly with medullar involvement, and/or bone metastasis. Patients typically suffer from poor general state, bone pain, and/or dyspnea. Laboratory abnormalities such as myelemia or erythromyelemia in peripheral blood are frequently observed. Incidence of coagulation disorders is increased, compared to other MAHA causes. BC-MAHA prognosis is dramatically poor. Treatments classically used in other MAHA causes, such as plasmapheresis or immunoglobulins, are inefficient. Urgent anti-neoplastic therapy may be the only effective treatment, associated to symptomatic therapies (transfusions, blood pressure control).

Performance of Diagnostic Scores in Thrombotic Microangiopathy Patients in the Intensive Care Unit: A Monocentric Study

Early thrombotic thrombocytopenic purpura (TTP) recognition is critical as this disease is almost always lethal if not treated promptly with therapeutic plasma exchanges. Currently, as ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity is not widely available in emergency, scores have been developed to help differentiating TTP from other thrombotic microangiopathies (TMAs). The aim of this work was to study the accuracy of these diagnostic scores in the intensive care unit (ICU) setting. Performance of both Coppo and PLASMIC scores was studied in a cohort of adult TMA patients requiring admission to one university hospital ICU from 2006 to 2017. Receiver operating characteristic (ROC) curves were established, and confidence intervals of the area under the curve (AUC) were determined. Multivariate logistic regression analysis was performed to identify parameters specifically associated with TTP, to compare diagnostic scores and to elaborate more accurate diagnostic models. During the study period, 154 TMA patients required ICU admission, including 99 (64.2%) TTP and 55 (35.7%) non-TTP patients. AUC under the ROC curve in predicting TTP was 0.86 (95% confidence interval [CI]: 0.81-0.92) for the Coppo score, 0.67 (95% CI: 0.58-0.76) for the PLASMIC score, and 0.86 (95% CI: 0.81-0.92) for platelet count alone. Platelet count ≤20 G/L, determined as the best cut-off rate for thrombocytopenia, performed similarly to the Coppo score and better than the PLASMIC score to differentiate TTP from non-TTP patients, both using AUC ROC curve and logistic regression. In a monocentric cohort of TMA patients requiring ICU admission, the PLASMIC score had limited performance for the diagnosis of TTP. The performance of the Coppo score was good but similar to a single highly discriminant item: platelet count ≤20 G/L at admission.

Circulating Von Willebrand factor and high molecular weight multimers as markers of endothelial injury predict COVID-19 in-hospital mortality

Background

Coronavirus disease 2019 (COVID-19) is a respiratory disease associated with endotheliitis and microthrombosis.

Objectives

To correlate endothelial dysfunction to in-hospital mortality in a bi-centric cohort of COVID-19 adult patients.

Methods

Consecutive ambulatory and hospitalized patients with laboratory-confirmed COVID-19 were enrolled. A panel of endothelial biomarkers and von Willebrand factor (VWF) multimers were measured in each patient ≤ 48 h following admission.

Results

Study enrolled 208 COVID-19 patients of whom 23 were mild outpatients and 189 patients hospitalized after admission. Most of endothelial biomarkers tested were found increased in the 89 critical patients transferred to intensive care unit. However, only von Willebrand factor antigen (VWF:Ag) scaled according to clinical severity, with levels significantly higher in critical patients (median 507%, IQR 428–596) compared to non-critical patients (288%, 230–350, p < 0.0001) or COVID-19 outpatients (144%, 133–198, p = 0.007). Moreover, VWF high molecular weight multimers (HMWM) were significantly higher in critical patients (median ratio 1.18, IQR 0.86–1.09) compared to non-critical patients (0.96, 1.04–1.39, p < 0.001). Among all endothelial biomarkers measured, ROC curve analysis identified a VWF:Ag cut-off of 423% as the best predictor for in-hospital mortality. The accuracy of VWF:Ag was further confirmed in a Kaplan–Meier estimator analysis and a Cox proportional Hazard model adjusted on age, BMI, C-reactive protein and d-dimer levels.

Conclusion

VWF:Ag is a relevant predictive factor for in-hospital mortality in COVID-19 patients. More than a biomarker, we hypothesize that VWF, including excess of HMWM forms, drives microthrombosis in COVID-19.

Diagnosis and follow-up of thrombotic thrombocytopenic purpura with an automated chemiluminescent ADAMTS13 activity immunoassay

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy (TMA) caused by a severe functional deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type I repeats-13), the specific von Willebrand factor (VWF) cleaving protease. ADAMTS13 activity is essential to diagnose TTP but remains challenging to assess, as reference ADAMTS13 activity assays are manual and time consuming. Current techniques also lack robustness in low detectable ADAMTS13 activity range, which could prove problematic for therapy-driven monitoring.

OBJECTIVES

The HemosIL AcuStar ADAMTS13 activity assay is a fast, automated chemiluminescent assay, the performance of which remains to be evaluated prospectively on very large cohorts of patients with TMA and in real-life conditions.

PATIENTS AND METHODS

Our study was conducted over two successive sequences: a retrospective evaluation followed by a "real-life" prospective evaluation. Overall, we evaluated the HemosIL AcuStar ADAMTS13 activity assay on 539 citrated plasma samples. We extensively studied linearity, limit of detection, contamination, intra-assay and interassay precisions with a specific focus on levels < 25 IU/dL. Diagnostic performances for the detection of < 10 IU/dL ADAMTS13 activity and overall method comparison were conducted with the fluorescence resonance energy transfer (FRETS)-VWF73 assay as the reference method.

RESULTS

Technical performance proved excellent. Robustness in low detectable ADAMTS13 activity range was good, potentially qualifying this assay for therapy-driven monitoring. Comparison with the FRETS-VWF73 assay was satisfactory (r 2 = .83, P < .0001) as were the diagnostic performances for acute-phase TTP (specificity, 99.7%; positive predictive value, 99.2%).

CONCLUSION

The HemosIL AcuStar ADAMTS13 activity assay is a fast, reliable, automated technique well adapted as a first-line ADAMTS13 activity assay for TTP diagnosis and follow-up.

Systemic lupus erythematosus presenting as thrombotic thrombocytopaenic purpura in a child: a diagnostic challenge

Thrombotic thrombocytopaenic purpura (TTP) is a life-threatening thrombotic microangiopathy characterised by microangiopathic haemolytic anaemia, thrombocytopaenia and organ ischaemia. TTP is caused by a severe functional deficiency of ADAMTS13 activity. We describe a 10-year-old girl presenting anaemia and thrombocytopaenia with schistocytes. Urine protein to creatinine ratio was within nephrotic range. ADAMTS13 activity was 0%, and no anti-ADAMTS13 antibodies were found. A renal biopsy showed deposits of IgG, C3 and C1q in the capillary membrane, compatible with class V lupus nephritis. Therapeutic plasma exchange (TPE) was performed in conjunction with therapy consisting of steroids and mycophenolate mofetil. After 11 months of follow-up, the patient remains in remission with normal ADAMTS13 activity. Although acquired TTP is a rare finding in children, differential diagnosis of thrombotic microangiopathy should include ADAMTS13 and the assay should be performed early. TTP treatment is based on TPE, although the underlying disease must be ruled out to optimise treatment and prevent relapse.

Reference range for ADAMTS13 antigen, activity and anti-ADAMTS13 antibody in the healthy adult Singapore population

INTRODUCTION

ADAMTS13 (A disintegrin-like and metalloproteinase with a thrombospondin type 1 motif, member 13) plays a fundamental role in the regulation of haemostasis and thrombosis. Its deficiency leads to an accumulation of ultra-large von Willebrand multimers, inducing spontaneous platelet aggregation, thrombosis in the microvasculature and thrombotic thrombocytopenic purpura (TTP), a condition with 90% mortality when left untreated. Promptly quantifying ADAMTS13 antigen, activity and autoantibody has a crucial role in the diagnosis and management of TTP and can help differentiate from other thrombotic microangiopathies (TMAs). Reference ranges for ADAMTS13 are generally derived from Caucasian patients. Given that polymorphism in the ADAMTS13 gene can be associated with variable ADAMTS13 levels, we aimed to establish the first reference range in Singapore and provide a crucial laboratory test for institutions here and elsewhere.

METHODS

150 healthy voluntary donors (75 men, 75 women), aged 21-60 years, with an ethnic mix mirroring Singapore's population profile, were recruited. ADAMTS13 antigen, activity and autoantibody levels were measured using the fluorescent resonance energy transfer-vWF73 and enzyme-linked immunosorbent assay methodologies.

RESULTS

Levels (activity, 0.65-1.79 IU/mL; antigen, 0.36-1.17 IU/mL; autoantibody, 1.4-12.5 U/mL) were not statistically different between the genders and various age groups.

CONCLUSION

TTP and TMAs are encountered in a wide range of specialties. The availability of new assays in Singapore will aid clinicians in the timely management of these conditions. Standardising reference ranges established for Singapore, against World Health Organization standards, allows the harmonisation of measurements between laboratories and for future research collaborations.

Changing epidemiology of acute kidney injury in pregnancy: A journey of four decades from a developing country

The incidence of acute kidney injury in pregnancy (P-AKI) has markedly decreased over the last three decades in India, particularly due to decreased incidence of postabortion AKI. However, P-AKI still accounts for 3%-5% of cases of total AKI. Postabortion sepsis has decreased to between 0.9% and 1.5% in 2014 from 9.4% in 1980-1990 in the new millennium. Currently, in India, majority of P-AKI (70%-90%) occurs in the postpartum period and in late 3^rd trimester similar to the developed countries, but causes are different. We observed that preeclampsia/eclampsia is the most common cause of P-AKI in the late 3^rd trimester and postpartum period followed by puerperal sepsis and postpartum hemorrhage (PPH). Both puerperal sepsis and PPH are treatable and preventable etiologies of P-AKI. Timely and aggressive management of antepartum hemorrhage (APH/PPH) and puerperal sepsis are required to reduce the burden of P-AKI in developing countries. Specific-pregnancy disorders such as P-aHUS/thrombotic thrombocytopenic purpura, pregnancy-associated thrombotic microangiopathy, and acute fatty liver of pregnancy are the uncommon/rare causes of P-AKI in India and possibly also because of the lack of awareness toward diagnosis. Despite decreasing incidence of P-AKI, fetal mortality remained high and unchanged. However, maternal mortality has decreased to 5% from initial high mortality of 20%-25%. The incidence and severity of renal cortical necrosis have significantly decreased at our center.

An Autopsy Case of Mixed Connective Tissue Disease Complicated by Thrombotic Thrombocytopenic Purpura

We herein report a patient with mixed connective tissue disease (MCTD) who had been stable for years but suddenly developed thrombotic thrombocytopenic purpura (TTP). The patient showed a clinical pentad of signs of TTP, low activity of ADAMTS13, and positivity of anti-ADAMTS13 antibodies. She did not respond to plasma exchange or steroid therapy and died five days after admission. An autopsy revealed microthrombi in the brain, heart, kidney, adrenal glands, esophageal submucosa, and bone marrow as well as diffuse alveolar hemorrhaging. Physicians should bear in mind that TTP can occur in MCTD patients regardless of disease activity.

Expert statement on the ICU management of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is fatal in 90% of patients if left untreated and must be diagnosed early to optimize patient outcomes. However, the very low incidence of TTP is an obstacle to the development of evidence-based clinical practice recommendations, and the very wide variability in survival rates across centers may be partly ascribable to differences in management strategies due to insufficient guidance. We therefore developed an expert statement to provide trustworthy guidance about the management of critically ill patients with TTP. As strong evidence was difficult to find in the literature, consensus building among experts could not be reported for most of the items. This expert statement is timely given the recent advances in the treatment of TTP, such as the use of rituximab and of the recently licensed drug caplacizumab, whose benefits will be maximized if the other components of the management strategy follow a standardized pattern. Finally, unanswered questions are identified as topics of future research on TTP.

Plasmic score applicability for the diagnosis of thrombotic microangiopathy associated with ADAMTS13-acquired deficiency in a developing country

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal disease that requires early diagnosis and treatment that can be made possible by applying the PLASMIC score. This study aims to evaluate this score applicability for patients with suspected TTP in a developing country.

METHODS

This was a retrospective study performed at a tertiary hospital in the northeastern region of Brazil. Patients were analyzed in two groups: ADAMTS13 activity <10% and activity >10%. Patients were stratified according to the PLASMIC score, and the level of agreement between the PLASMIC score and the ADAMTS13 activity was evaluated.

RESULTS

Eight patients with thrombotic microangiopathy were included. Four patients had ADAMTS13 activity <10%, all with a PLASMIC score =6. The other four had ADAMTS13 activity >10%, all with a score <6. Based on a score =6 for presumptive diagnosis of TTP, we attained a 100% diagnostic accuracy in our sample. The PLASMIC score was also able to accurately predict response to plasma exchange and the risk of long-term unfavorable outcomes.

CONCLUSIONS

The reproducibility of the PLASMIC score was quite satisfactory in our sample. It accurately discriminates between patients who had ADAMTS13 deficiency and those with normal enzyme activity, precluding the need for specific laboratory evaluation, which is not always available. This score can be useful for an early diagnosis and indicates which patients will benefit from the treatment in developing countries.

Thrombotic thrombocytopenic purpura: Toward targeted therapy and precision medicine

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy characterized by severe congenital or immune-mediated deficiency in ADAMTS13, the enzyme that cleaves von Willebrand factor multimers. This rare condition leads invariably and rapidly to a fatal outcome in the absence of treatment, and therefore raises multiple diagnostic and therapeutic challenges. The novel concepts and mechanisms identified in the laboratory for this disease have been rapidly and successfully translated into the clinic for the benefit of patients, making TTP an archetypal disease that has benefited from targeted therapies. After decades of empirical treatment with plasma exchange, identification of ADAMTS13 as the key enzyme involved in TTP pathophysiology provided an explanation for the remarkable efficacy of plasma administration, in which the missing enzyme is replenished, and paved the way for development of a recombinant form of the enzyme. Similarly, the demonstration of a major role of anti-ADAMTS13 antibodies through models of passive transfer of autoimmunity spurred development of immunomodulatory strategies based on B-cell depletion. More recently, an inhibitor of the platelet-von Willebrand factor interaction demonstrated efficacy in large clinical trials through prevention of formation of further microthrombi and protection of organs from ischemia. These translational breakthroughs in TTP are described in our review.

The role of ADAMTS13 testing in the diagnosis and management of thrombotic microangiopathies and thrombosis

ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, 13) is a metalloprotease responsible for cleavage of ultra-large von Willebrand factor (VWF) multimers. Severely deficient activity of the protease can trigger an acute episode of thrombotic thrombocytopenic purpura (TTP). Our understanding of the pathophysiology of TTP has allowed us to grasp the important role of ADAMTS13 in other thrombotic microangiopathies (TMAs) and thrombotic disorders, such as ischemic stroke and coronary artery disease. Through its action on VWF, ADAMTS13 can have prothrombotic and proinflammatory properties, not only when its activity is severely deficient, but also when it is only moderately low. Here, we will discuss the biology of ADAMTS13 and the different assays developed to evaluate its function in the context of TTP, in the acute setting and during follow-up. We will also discuss the latest evidence regarding the role of ADAMTS13 in other TMAs, stroke, and cardiovascular disease. This information will be useful for clinicians not only when evaluating patients who present with microangiopathic hemolytic anemia and thrombocytopenia, but also when making clinical decisions regarding the follow-up of patients with TTP.

Ticagrelor-induced thrombotic thrombocytopenic purpura: A case report and review of the literature

RATIONALE

Ticagrelor, a new type of P2Y12 receptor antagonist, has been highly recommended to be used in acute coronary syndrome by the latest guideline, but its side effects are not well-known. We seek to illustrate a potential fatal condition, thrombotic thrombocytopenic purpura (TTP), caused by ticagrelor.

PATIENT CONCERNS

An 87-year-old man who had been prescribed with ticagrelor for 2 months after ST-elevation myocardial infarction (STEMI), presented with severe thrombocytopenia, anemia, renal and liver dysfunction, heart failure and fever.

DIAGNOSES

Peripheral blood smear showed schistocytosis, and a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) activity is low, with normal initial coagulation tests, which were compatible with a diagnosis of TTP.

INTERVENTIONS

After cessation of ticagrelor and initiation of therapeutic plasma exchange, our patient recovered.

OUTCOMES

Re-administration of ticagrelor aggravated TTP and led the patient to death.

LESSONS

Clinicians should be aware of the possibility of ticagrelor-induced TTP in patients with a history of recent myocardial infarction; It is of crucial significance to discontinue and never reuse ticagrelor as long as it is suspected to be implicated in TTP.

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.

Clinical features and outcomes in patients with thrombotic microangiopathy not associated with severe ADAMTS13 deficiency

BACKGROUND

The a disintegrin and metalloprotease with thrombospondin type 1 motifs, member 13 (ADAMTS13) activity assay has become important in distinguishing autoimmune thrombotic thrombocytopenic purpura from other forms of thrombotic microangiopathy (TMA). Although the significance of severe deficiency in ADAMTS13 (activity levels 10% or less) has been well defined, little data are available on the clinical importance of mild to moderate deficiency (activity levels 11%-70%) among patients with TMA.

STUDY DESIGN AND METHODS

We conducted a retrospective study using the Harvard TMA Research Collaborative Registry. Among 254 patients who met the inclusion criteria for TMA, 186 patients with ADAMTS13 activity levels greater than 10% were divided into moderate-deficiency (11%-40%), mild-deficiency (41%-70%), and no-deficiency (greater than 70%).

RESULTS

Compared with mild or no deficiency, moderate ADAMTS13 deficiency correlated with older age; higher bilirubin and international normalized ratio; and increased frequency of sepsis, shock, or multiorgan failure. Platelet counts, lactate dehydrogenase levels, and the presence of renal or neurologic dysfunction did not vary across the three patient cohorts. While moderate ADAMTS13 deficiency was associated with increased 90-day mortality in univariate analysis, this association was no longer significant in multivariate analysis. Variables that independetly predicted 90-day mortality in this cohort of patients included Charlson comorbidity index, alanine aminotransferase level, platelet count, creatinine, and the presence of sepsis, shock, or multiorgan failure.

CONCLUSION

Moderately deficient ADAMTS13 activity identifies a cohort of patients with TMA who are at increased risk for 90-day mortality. The ADAMTS13 activity level in this group is not an independent predictor of poor outcomes but instead appears to be a marker of disease acuity.

Thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, severe thrombocytopenia, and organ ischemia linked to disseminated microvascular platelet rich-thrombi. TTP is specifically related to a severe deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13), the specific von Willebrand factor-cleaving protease. ADAMTS13 deficiency is most frequently acquired via ADAMTS13 autoantibodies, but rarely, it is inherited via mutations of the ADAMTS13 gene. The first acute episode of TTP usually occurs during adulthood, with a predominant anti-ADAMTS13 autoimmune etiology. In rare cases, however, TTP begins as soon as childhood, with frequent inherited forms. TTP is ∼2-fold more frequent in women, and its outcome is characterized by a relapsing tendency. Rapid recognition of TTP is crucial to initiate appropriate treatment. The first-line therapy for acute TTP is based on daily therapeutic plasma exchange supplying deficient ADAMTS13, with or without steroids. Additional immune modulators targeting ADAMTS13 autoantibodies are mainly based on steroids and the humanized anti-CD20 monoclonal antibody rituximab. In refractory or unresponsive TTP, more intensive therapies including twice-daily plasma exchange; pulses of cyclophosphamide, vincristine, or cyclosporine A; or salvage splenectomy are considered. New drugs including N-acetylcysteine, bortezomib, recombinant ADAMTS13, and caplacizumab show promise in the management of TTP. Also, long-term follow-up of patients with TTP is crucial to identify the occurrence of other autoimmune diseases, to control relapses, and to evaluate psychophysical sequelae. Further development of both patients’ registries worldwide and innovative drugs is still needed to improve TTP management.

Acute Kidney Injury in Pregnancy-specific Disorders

The incidence of acute kidney injury in pregnancy (P-AKI) has declined significantly over the last three decades in developing countries. However, it is still associated with significant fetomaternal mortality and morbidity. The diagnosis of P-AKI is based on the serum creatinine increase. The usual formulas for estimating glomerular filtration rate (GFR) are not validated in this population. The incidence of P-AKI with respect to total AKI cases has decreased in the last three decades from 25% in 1980s to 9% in 2000s at our centre. During the first trimester of gestation, AKI develops most often due to septic abortion or hyperemesis gravidarum. Septic abortion related AKI with respect to total AKI decreased from 9% to 5% in our study. Prevention of unwanted pregnancy and avoidance of septic abortion are keys to eliminate abortion associated AKI in early pregnancy. However, we have not seen AKI on account of hyperemesis gravidarum over a period of 33 years at our center. In the third trimester, the differential diagnosis of AKI in association with pregnancy specific conditions namely preeclampsia/HELLP syndrome, acute fatty liver of pregnancy and thrombotic microangiopathies of pregnancy (P-TMA) is more challenging, because these 3 conditions share several clinical features of thrombotic microangiopathy which makes the diagnosis very difficult on clinical grounds. It is imperative to distinguish these conditions to make appropriate therapeutic decisions. Typically, AFLP and HELLP syndrome improve after delivery of the fetus, whereas plasma exchange is the first-line treatment for pregnancy associated thrombotic microangioathies (P-TMA). We observed that preclampsia/eclampsia is the most common cause of AKI in late third trimester and postpartum periods followed by puerperal sepsis and postpartum hemorrhage. Pregnancy-associated thrombotic microangiopathies (aHUS/TTP) and AFLP are rare causes of AKI during pregnancy in developing countries.

Child-onset and adolescent-onset acquired thrombotic thrombocytopenic purpura with severe ADAMTS13 deficiency: a cohort study of the French national registry for thrombotic microangiopathy

BACKGROUND

Thrombotic thrombocytopenic purpura is a rare thrombotic microangiopathy, related to a severe ADAMTS13 deficiency (a disintegrin and metalloprotease with thromboSpondin type 1 repeats, member 13; activity <10% of normal). Childhood-onset thrombotic thrombocytopenic purpura is very rare and initially often misdiagnosed, especially when ADAMTS13 deficiency is acquired (ie, not linked to inherited mutations of the ADAMTS13 gene). We aimed to investigate initial presentation, management, and outcome of acquired thrombotic thrombocytopenic purpura in children.

METHODS

Between Jan 1, 2000, and Dec 31, 2015, we studied a cohort of patients with child-onset and adolescent-onset acquired thrombotic thrombocytopenic purpura included in the French national registry for thrombotic microangiopathies at presentation and during follow up. The inclusion criteria were: first episode before age 18 years; ADAMTS13 activity less than 10% of normal at presentation; positive anti-ADAMTS13 autoantibodies during an episode, or a recovery of ADAMTS13 activity in remission, or both. ADAMTS13 activity and anti-ADAMTS13 autoantibodies were investigated by a central laboratory, and medical records were extensively reviewed to collect clinical and biological features with a standardised form. This study is registered with ClinicalTrials.gov, number NCT00426686.

FINDINGS

We enrolled 973 patients with childhood-onset thrombotic microangiopathy, of whom 74 had a severe ADAMTS13 deficiency (activity <10%) at presentation. 24 patients had an inherited thrombotic thrombocytopenic purpura also known as Upshaw-Schulman syndrome and five did not have follow-up data available, thus 45 children had acquired thrombotic thrombocytopenic purpura and were included in our database at presentation. 25 (56%) patients had idiopathic disease and 20 (44%) had miscellaneous associated clinical conditions. At diagnosis, median age was 13 years (IQR 7-16, range 4 months-17 years), with a sex ratio of 2·5 girls to 1 boy. Anti-ADAMTS13 autoantibodies were positive in 37 (82%) of 45 patients (24 [96%] of 25 idiopathic cases and 13 [65%] of 20 non-idiopathic cases). 39 (87%) of 45 patients were given plasma therapy and 21 (47%) received additional rituximab. Four (9%) children died after the first thrombotic thrombocytopenic purpura episode. Long-term follow up of the 41 survivors showed that ten (24%) patients relapsed and systemic lupus erythematosus occurred in two (5%) patients. Preemptive rituximab was used in seven (17%) of 41 patients with acquired thrombotic thrombocytopenic purpura.

INTERPRETATION

Our study shows that child-onset and adolescent-onset acquired thrombotic thrombocytopenic purpura have specific clinical, biological and therapeutic features. Long-term follow-up is crucial to prevent relapses of the disease, to identify the occurrence of autoimmune disorders, and to evaluate consequences on social life. Child-onset and adolescent-onset acquired thrombotic thrombocytopenic purpura is a crucial diagnosis in the field of paediatric haematologic cytopenias because it is a life-threatening disease requiring a specific management.

FUNDING

Assistance Publique-Hôpitaux de Paris, France.

Clinical Practice Guidelines for the Management of Atypical Hemolytic Uremic Syndrome in Korea

Atypical hemolytic uremic syndrome (aHUS) is a rare syndrome characterized by micro-angiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The major pathogenesis of aHUS involves dysregulation of the complement system. Eculizumab, which blocks complement C5 activation, has recently been proven as an effective agent. Delayed diagnosis and treatment of aHUS can cause death or end-stage renal disease. Therefore, a diagnosis that differentiates aHUS from other forms of thrombotic microangiopathy is very important for appropriate management. These guidelines aim to offer recommendations for the diagnosis and treatment of patients with aHUS in Korea. The guidelines have largely been adopted from the current guidelines due to the lack of evidence concerning the Korean population.

Thrombocytopenia in Critical Care Patients

Thrombocytopenia is a common laboratory finding in the intensive care unit (ICU) patient. Because the causes can range from laboratory artifact to life-threatening processes such as thrombotic thrombocytopenic purpura (TTP), identifying the cause of thrombocytopenia is important. In the evaluation of the thrombocytopenia patient, one should incorporate all clinical clues such as why the patient is in the hospital, medications the patient is on, and other abnormal laboratory findings. One should ensure that the patient does not suffer from heparin-induced thrombocytopenia (HIT) or one of the thrombotic microangiopathies (TMs). HIT can present in any patient on heparin and requires specific testing and antithrombotic therapy. TMs cover a spectrum of disease ranging from TTP to pregnancy complications and can have a variety of presentations. Management of disseminated intravascular coagulation depends on the patient’s condition and complication. Other causes of ICU thrombocytopenia include sepsis, medication side effects, post-transfusion purpura, catastrophic anti phospholipid antibody disease, and immune thrombocytopenia.

[Incomplete thrombotic microangiopathy as a variant of hemolytic-uremic syndrome]

The described case illustrates difficulties in diagnosing atypical hemolytic-uremic syndrome (aHUS) in incomplete thrombotic microangiopathy (TMA) in the absence of thrombocytopenia, one of the signs of the classic triad of aHUS, which has resulted in the delayed verification of its diagnosis and in progressive kidney injury. The paper discusses the need to carry out kidney biopsy and to include sHUS in both the presence of a complete set of symptoms of this disease and in the absence of one of them into a range of diagnostic search.

Acute thrombotic thrombocytopenic purpura after pneumococcal vaccination

We report the case of a 68-year-old woman with acute thrombotic thrombocytopenic purpura (TTP) that developed after pneumococcal vaccination. She was found in a confusional state with high fever 15 days after vaccination. Laboratory data showed hemolytic anemia and thrombocytopenia, and blood smear showed fragmented erythrocytes. TTP was diagnosed based on the clinical presentation, and was subsequently confirmed by the absence of ADAMTS13 activity and the presence of inhibitor against ADAMTS13 in serum. She was successfully treated using plasma exchange and corticosteroids, and no recurrence has been identified. This appears to represent the first report of TTP following pneumococcal vaccination.

von Willebrand factor fibers promote cancer-associated platelet aggregation in malignant melanoma of mice and humans

Tumor-mediated procoagulatory activity leads to venous thromboembolism and supports metastasis in cancer patients. A prerequisite for metastasis formation is the interaction of cancer cells with endothelial cells (ECs) followed by their extravasation. Although it is known that activation of ECs and the release of the procoagulatory protein von Willebrand factor (VWF) is essential for malignancy, the underlying mechanisms remain poorly understood. We hypothesized that VWF fibers in tumor vessels promote tumor-associated thromboembolism and metastasis. Using in vitro settings, mouse models, and human tumor samples, we showed that melanoma cells activate ECs followed by the luminal release of VWF fibers and platelet aggregation in tumor microvessels. Analysis of human blood samples and tumor tissue revealed that a promoted VWF release combined with a local inhibition of proteolytic activity and protein expression of ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type I repeats 13) accounts for this procoagulatory milieu. Blocking endothelial cell activation by the low-molecular-weight heparin tinzaparin was accompanied by a lack of VWF networks and inhibited tumor progression in a transgenic mouse model. Our findings implicate a mechanism wherein tumor-derived vascular endothelial growth factor-A (VEGF-A) promotes tumor progression and angiogenesis. Thus, targeting EC activation envisions new therapeutic strategies attenuating tumor-related angiogenesis and coagulation.

Clinical utility of ADAMTS-13 testing in suspected thrombotic microangiopathy: an audit of ADAMTS-13 activity assay requests in routine practice from a tertiary hospital

AIMS

Differentiation between thrombotic thrombocytopenic purpura (TTP) and other microangiopathic haemolytic anaemia (MAHA) processes can be difficult. Since the documentation of ADAMTS-13 deficiency in TTP, several ADAMTS-13 activity assays have been developed for use in the diagnosis of TTP and/or other microangiopathic disorders. We reviewed the clinical utility of ADAMTS-13 activity testing in suspected TTP, as used in routine clinical practice in a tertiary referral hospital.

METHODS

All requests for ADAMTS-13 activity levels performed at our institution after introduction of the assay were retrospectively audited with respect to clinical diagnosis and results.

RESULTS

In total 57 individual patients were tested, of whom only 46% had a MAHA process. Severe ADAMTS-13 deficiency was present in five TTP patients and in one patient with fulminant hepatic failure.

CONCLUSIONS

Our experience suggests that severely reduced levels are relatively specific for TTP, but may also occur in fulminant hepatic failure. Patients without MAHA may have reduced ADAMTS-13 activity and there is significant overlap in the range of ADAMTS-13 activity seen in non-TTP MAHA diagnoses. This supports the observation that outside the diagnosis and (possible) follow-up of suspected idiopathic TTP, the ADAMTS-13 activity assay has limited clinical utility. Further education about the role of ADAMTS-13 activity testing is needed.

Differing tales of two patients after receiving a kidney transplant from a donor with disseminated intravascular coagulation

In order to decrease the time on the deceased donor kidney wait list and to have more organs available, criteria for acceptable organs for transplant could be made less stringent. There are reports of successful recipient outcomes using kidney donors presenting with disseminated intravascular coagulation (DIC). We report a unique circumstance where two patients received kidneys from the same deceased donor who had DIC; one patient developed thrombotic microangiopathy (TMA) while the other did not. This difference in outcome may indicate that both donor and recipient factors contribute to the development of posttransplant TMA.