Thrombotic thrombocytopenic purpura: a thrombotic disorder caused by ADAMTS13 deficiency

A Successfully Treated COVID-19 Vaccine Induced Immune Thrombocytopenic Purpura

Immune Thrombocytopenic Purpura (ITP) is a life-threatening condition where an accurate initial assessment is essential to be able to offer the proper therapy in a timely matter to improve the outcome of the patient. Here, we present a case of ITP secondary to the coronavirus disease 2019 (COVID-19) vaccine (BioNTech, Pfizer vaccine). A 61-year-old obese African American female presented to the emergency room (ER) from a clinic with a platelet count of 11k/ul 21 days after she received the second dose of the BioNTech, Pfizer vaccine. The patient was immediately started on intravenous immunoglobulin (IVIG) 1g/kg twice daily (bid) and dexamethasone 20 mg IV every 12 hrs (q12h). The next day, the platelet count increased to 63 k/ul, and after the second dose of IVIG, the platelet count improved to 122 k/ul and trended up. The early detection of ITP induced by the mRNA COVID-19 vaccine is determinant to guide the early and proper therapy with immunoglobulins and steroids to improve the outcome of our patients.

A comprehensive evaluation of stable expression "hot spot" in the ScltI gene of Chinese hamster ovary cells

The Chinese hamster ovary (CHO) cell is the most widely used biopharmaceutical expression system, but its long-term expression is unstable. This issue can be effectively addressed by site-specific integration of exogenous genes into the genome. Therefore, exogenous protein sites with stable expression in the CHO cell genome must be identified. CRISPR/Cas9 technology was used in this study to integrate various exogenous genes into the ScltI site as a "hot spot" at the CHO-K1 cell genome NW_003614095.1, and the stability and adaptability of exogenous genes expressed at the site were investigated. Flow cytometry sorting technology was used to obtain positive monoclonal cell lines that expressed either intracellular protein green fluorescent protein (EGFP) or secretory protein human serum albumin (HSA). For 60 passages, the positive monoclonal cell lines' cell growth cycles and exogenous protein expression were both observed. The results demonstrated that integrating the gene encoding exogenous proteins into the ScltI site had no effect on cell growth. The fluorescence intensity of EGFP was similar after 60 passages, and the expression of HSA increased slightly. Additionally, the super-monomeric protein VWF hydrolase (ADAMTS13) (190 kDa), human coagulation factor VII (FVII) (55 kDa), and interferon α2b (12 kDa) were integrated into the ScltI site for expression. In conclusion, the site located in the first exon of the ScltI gene within the CHO-K1 cell genome NW_003614095.1 is an ideal "hot spot" for the stable expression of various exogenous proteins. KEY POINTS: • The site-specific integration strategy of an exogenous gene in CHO cells was established for the ScltI site. • The genes for EGFP and HSA were site-directed integrated and stably expressed at the ScltI site. • The ScltI site fulfills the expression of exogenous proteins of different molecular weight sizes (15-190 kDa).

Cardiovascular disease is a leading cause of mortality among TTP survivors in clinical remission

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) survivors experience high rates of adverse health sequelae and increased mortality over long-term follow-up. We conducted this multicenter cohort study to evaluate long-term mortality and causes of death in iTTP survivors. Between 2003 and 2020, 222 patients were enrolled in the Ohio State University and Johns Hopkins TTP registries and followed for a median of 4.5 (interquartile range [IQR], 75 0.4-11.5) years. Nine patients died during their first iTTP episode, and 29 patients died during follow-up. Mortality rate was 1.8 times higher than expected from an age-, sex-, and race-adjusted reference population. Cardiovascular disease was a leading primary cause of death (27.6%) tied with relapsed iTTP (27.6%), followed by malignancy (20.7%), infection (13.8%), and other causes (10.3%). Male sex (hazard ratio [HR], 3.74; 95% confidence interval [CI], 1.65-8.48), increasing age (HR, 1.04; 95% CI, 1.01-1.07), and number of iTTP episodes (HR, 1.10; 95% CI, 1.01-1.20) were associated with mortality in a model adjusted for African American race (HR, 0.70; 95% CI, 0.30-1.65), hypertension (HR, 0.47; 95% CI, 0.20-1.08), chronic kidney disease (HR 1.46; 95% CI, 0.65-3.30), and site (HR, 1.46; 95% CI, 0.64-3.30). There was a trend toward shorter survival in patients with lower ADAMTS13 activity during remission (P = .078). Our study highlights the need for survivorship care and investigation focused on cardiovascular disease and early mortality in TTP survivors.

Immunothrombosis and new-onset atrial fibrillation in the general population: the Rotterdam Study

Background

Atrial fibrillation (AF) is the most common age-related cardiac arrhythmia. The etiology underlying AF is still largely unknown. At the intersection of the innate immune system and hemostasis, immunothrombosis may be a possible cause of atrial remodeling, and therefore be an underlying cause of AF.

Methods

From 1990 to 2014, we followed participants aged 55 and over, free from AF at inclusion. Immunothrombosis factors fibrinogen, von Willebrand factor, ADAMTS13, and neutrophil extracellular traps (NETs) levels were measured at baseline. Participants were followed until either onset of AF, loss-to-follow-up, or reaching the end-date of 01-01-2014. Cox proportional hazard modelling was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusted for cardiovascular risk factors.

Results

We followed 6174 participants (mean age 69.1 years, 57% women) for a median follow-up time of 12.8 years. 364 men (13.7%, incidence rate 13.0/1000 person-years) and 365 women (10.4%, incidence rate 8.9/1000 person-years) developed AF. We found no significant association between markers of immunothrombosis and new-onset AF after adjusting for cardiovascular risk factors [HR 1.00 (95% CI 0.93–1.08) for fibrinogen, 1.04 (0.97–1.12) for von Willebrand factor, 1.00 (1.00–1.01) for ADAMTS13, and 1.01 (0.94–1.09) for NETs]. In addition, we found no differences in associations between men and women.

Conclusion

We found no associations between markers of immunothrombosis and new-onset AF in the general population. Inflammation and immunothrombosis may be associated with AF through other cardiovascular risk factors or predisposing conditions of AF. Our findings challenge the added value of biomarkers in AF risk prediction.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01938-4.

Von Willebrand factor, ADAMTS13 and mortality in dialysis patients

BACKGROUND

Von Willebrand Factor (VWF) multimers are cleaved into smaller and less coagulant forms by the metalloprotease ADAMTS13. The aim of this study was to investigate the association between VWF and ADAMTS13 and mortality in dialysis patients.

METHODS

We prospectively followed 956 dialysis patients. VWF levels and ADAMTS13 activity were measured. Cox proportional hazard analyses were used to calculate hazard ratios (HRs) with 95 % confidence intervals (CIs) to investigate the association between quartiles of VWF levels and ADAMTS13 activity and all-cause mortality. HRs were adjusted for age, sex, body mass index, cardiovascular disease, dialysis modality, primary kidney disease, use of antithrombotic medication, systolic blood pressure, albumin, C-reactive protein and residual GFR.

RESULTS

Of the 956 dialysis patients, 288 dialysis patients died within three years (mortality rate 151 per 1000 person-years). The highest quartile of VWF as compared with lower levels of VWF was associated with a 1.4-fold (95 %CI 1.1-1.8) increased mortality risk after adjustment. The lowest quartile of ADAMTS13 activity as compared with other quartiles was associated with a 1.3-fold (95 %CI 1.0-1.7) increased mortality risk after adjustment. The combination of the highest VWF quartile and lowest ADAMTS13 quartile was associated with a 2.0-fold (95 %CI 1.3-3.0) increased mortality risk as compared with the combination of the lowest VWF quartile and highest ADAMTS13 quartile.

CONCLUSIONS

High VWF levels and low ADAMTS13 activity were associated with increased mortality risks in dialysis patients.

Cerebral Microangiopathy in Two Dogs with Cutaneous and Renal Glomerular Vasculopathy

Cutaneous and renal glomerular vasculopathy (CRGV) is an emerging disease in the UK, but its aetiology remains unclear. It is considered a thrombotic microangiopathy (TMA) in which the kidney and skin are the most commonly affected organs. We now document two cases of CRGV with brain lesions, which may have accounted for neurological signs displayed by these animals. The histopathological brain lesions were similar to TMA lesions in humans with thrombotic thrombocytopaenic purpura (TTP) and complement-mediated haemolytic uraemic syndrome (CM-HUS), in which the neurological signs are more associated with TMA than with any systemic disease or electrolyte imbalance. Fibrinoid necrosis in brain arterioles and associated lesions in these dogs were similar to those in human CM-HUS, indicating that the alternative complement pathway may play an important role in the pathophysiology of CRGV.

How I treat thrombotic thrombocytopenic purpura in pregnancy

Thrombotic thrombocytopenic purpura (TTP) is an acute, life-threatening thrombotic microangiopathy (TMA) caused by acquired or congenital severe deficiency of ADAMTS13. Pregnancy is a recognized risk factor for precipitating acute (first or recurrent) episodes of TTP. Differential diagnosis with other TMAs is particularly difficult when the first TTP event occurs during pregnancy; a high index of suspicion and prompt recognition of TTP are essential for achieving a good maternal and fetal outcome. An accurate distinction between congenital and acquired cases of pregnancy-related TTP is mandatory for safe subsequent pregnancy planning. In this article, we summarize the current knowledge on pregnancy-associated TTP and describe how we manage TTP during pregnancy in our clinical practice.

Atypical Presentation of Thrombotic Thrombocytopenic Purpura without Hematological Features

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease, usually diagnosed with high index of suspicion. The pathophysiology of TTP is due to severe deficiency of von Willebrand factor cleaving protease, known as ADAMTS 13. Early diagnosis is crucial as without treatment TTP is associated with high mortality rate. Plasma exchange is currently the mainstay of treatment. Nonetheless, the classical pentad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, neurological dysfunction, kidney dysfunction and fever are seen only in 40 percent of the patients. MAHA and thrombocytopenia are the common presenting features. Presentation with thrombotic complication without hematological features (MAHA and thrombocytopenia) is rare and makes the diagnosis difficult. Herein, we report an unusual presentation of a 53-year-old male, who was initially presented in 2014 with classical features of TTP, however had an atypical presentation of TTP in 2016 with only neurological features without hematological features.

Thrombotic Thrombocytopenic Purpura Associated with Myelodysplastic Syndrome

Myelodysplasia and thrombotic thrombocytopenic purpura (TTP) are both rare diseases. TTP is a blood abnormality in which blood clots form in blood vessels leading to fatal outcomes. Myelodysplastic syndrome is a group of disorders caused by poorly formed blood cells or ones that do not work properly. We are hereby presenting the case of a 69-year-old female who presented with anemia, thrombocytopenia, changes in mental status and reduced kidney function, and further investigations revealed that the patient had underlying myelodysplasia.

Formation and Resolution of Pial Microvascular Thrombosis in a Mouse Model of Thrombotic Thrombocytopenic Purpura

OBJECTIVE

Microvascular thrombosis is the hallmark pathology of thrombotic thrombocytopenic purpura (TTP), a rare life-threatening disease. Neurological dysfunction is present in over 90% of patients with TTP, and TTP can cause long-lasting neurological damage or death. However, the pathophysiology of microvascular thrombosis in the brain is not well studied to date. Here, we investigate the formation and resolution of thrombosis in pial microvessels. Approach and Results: Using a cranial intravital microscopy in well-established mouse models of congenital TTP induced by infusion of recombinant VWF (von Willebrand factor), we found that soluble VWF, at high concentration, adheres to the endothelium of the vessel wall, self-associates, and initiates platelet adhesion resulting in the formation of pial microvascular thrombosis in ADAMTS13^-/- (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) mice. Importantly, VWF-mediated pial microvascular thrombosis occurred without vascular injury to the brain, and thrombi consisted of resting platelets adhered onto ultra-large VWF without fibrin in the brain in rVWF (recombinant VWF) challenged ADAMTS13^-/- mice. Prophylactic treatment with recombinant ADAMTS13 (BAX930) effectively prevented the onset of the VWF-mediated microvascular thrombosis and therapeutic treatment with BAX930 acutely resolved the preexisting or growing thrombi in the brain of ADAMTS13^-/- mice after rVWF challenge. The absence of platelet activation and fibrin formation within VWF-mediated thrombi and efficacy of BAX930 was confirmed with an endothelial-driven VWF-mediated microvascular thrombosis model in mice.

CONCLUSIONS

Our results provide important insight into the initiation and development of microvascular thrombi in mouse models that mimics TTP and indicate that rADAMTS13 could be an effective interventional therapy for microvascular thrombosis, the hallmark pathology in TTP.

Domain-specific mechanical modulation of VWF-ADAMTS13 interaction

Hemodynamic forces activate the Von Willebrand factor (VWF) and facilitate its cleavage by a disintegrin and metalloprotease with thrombospondin motifs-13 (ADAMTS13), reducing the adhesive activity of VWF. Biochemical assays have mapped the binding sites on both molecules. However, these assays require incubation of two molecules for a period beyond the time allowed in flowing blood. We used a single-molecule technique to examine these rapid, transient, and mechanically modulated molecular interactions in short times under forces to mimic what happens in circulation. Wild-type ADAMTS13 and two truncation variants that either lacked the C-terminal thrombospondin motif-7 to the CUB domain (MP-TSP6) or contained only the two CUB domains (CUB) were characterized for interactions with coiled VWF, flow-elongated VWF, and a VWF A1A2A3 tridomain. These interactions exhibited distinctive patterns of calcium dependency, binding affinity, and force-regulated lifetime. The results suggest that 1) ADAMTS13 binds coiled VWF primarily through CUB in a calcium-dependent manner via a site(s) outside A1A2A3, 2) ADAMTS13 binds flow-extended VWF predominantly through MP-TSP6 via a site(s) different from the one(s) at A1A2A3; and 3) ADAMTS13 binds A1A2A3 through MP-TSP6 in a Ca²⁺-dependent manner to autoinhibit another Ca²⁺-independent binding site on CUB. These data reveal that multiple sites on both molecules are involved in mechanically modulated VWF–ADAMTS13 interaction.

von Willebrand factor/ADAMTS-13 interactions at birth: implications for thrombosis in the neonatal period

von Willebrand factor (VWF) and its cleaving protease ADAMTS-13 (A Disintegrin and Metalloproteinase with Thrombospondin type 1 motif, member 13) are essential components to hemostasis. These plasma proteins have also been implicated in a number of disease states, including those affecting children. The best described abnormality is the congenital form of thrombotic thrombocytopenic purpura (TTP) resulting from germline mutations in the ADAMTS-13 gene. The VWF/ADAMTS-13 interaction has more recently emerged as a causative risk factor in the pathogenesis of pediatric stroke and secondary microangiopathies. There is now increasing interest and need to measure these coagulation factors during the neonatal period and throughout childhood. Methods adopted from a multitude of technically diverging studies have been used to understand their role during this period. To date, studies of VWF/ADAMTS-13 in this group of patients have reported conflicting results, which makes interpreting values in the clinical setting especially challenging. In this review we describe the historical evolution of the methodology used to measure VWF/ADAMTS-13 and how it may influence the results obtained during the first days of life. We review the individual assays used to analyze VWF/ADAMTS-13 as well as published reference values. Finally, we bring attention to the potential pathophysiologic role of VWF/ADAMTS-13 in neonatal thrombosis. This has significant implications because the pathologic processes that explain thrombosis in neonates remain poorly characterized and thromboembolism remains a significant source of morbidity and mortality, particularly in sick children.

Thrombocytopenia in Intensive Care Unit

How to cite this article: Aluru N, Samavedam S. Thrombocytopenia in Intensive Care Unit. Indian J Crit Care Med 2019;23(Suppl 3):S185–S188.

Thrombotic thrombocytopenic purpura as the first presentation in systemic lupus erythematosus

Thrombotic thrombocytopenic purpura (TTP) is an uncommon, life-threatening disease characterized by severe thrombocytopenia, microangiopathic haemolytic anaemia, neurologic abnormalities, renal insufficiency, and fever commonly associated with infections, malignancy, drugs, and autoimmune diseases. Coexistence of TTP with systemic lupus erythematosus (SLE) is extremely rare, and the emergence of the full manifestation of SLE starting with TTP is even rarer. Black people due to genetic risk factors are at increased risk of TTP. In the present article the authors describe the case of a Nigerian woman who developed classical features of TTP as the first manifestation of SLE. The patient's condition was stabilized after treatment with intravenous pulses of methylprednisolone and subsequently on oral prednisolone and hydroxychloroquine treatment.

Thrombotic Thrombocytopenic Purpura Associated with Dermatomyositis

Dermatomyositis and thrombotic thrombocytopenic purpura (TTP) are both rare diseases. TTP is a blood abnormality in which blood clots form in blood vessels leading to fatal outcomes. Dermatomyositis is an inflammatory myopathy which causes a distinctive skin rash and muscle weakness. We are hereby presenting the case of a 27-year-old female who presented with characteristic skin findings on the face pathognomic of dermatomyositis and further investigation revealed that she had underlying TTP.

Acute kidney injury in a patient with hemolytic anemia and thrombocytopenia

Atypical hemolytic uremic syndrome (HUS) is clinically difficult to distinguish from HUS and thrombotic thrombocytopenic purpura. Atypical HUS results from dysregulation of complement activation causing thrombotic microangiopathy affecting multiple organ systems. Atypical HUS is associated with high morbidity and mortality, making early recognition and appropriate therapy necessary to improve patient outcomes.

Differentially regulated ADAMTS1, 8, 9, and 18 in pancreas adenocarcinoma

Introduction

Despite recent diagnostic and therapeutic improvements, pancreas cancer remains one of the highly lethal cancers. The extracellular matrix (ECM) is a physiological barrier that limits the spread of cancer cells into surrounding tissues and distant organs. Disintegrin and metalloprotease with thrombospondin motifs (ADAMTS) is a family of 19 proteases, which is involved in various biological processes such as ECM remodelling and anti-angiogenesis.

Aim

To investigate the expression of ADAMTS1, 8, 9, and 18 proteinases in pancreas adenocarcinoma and its nodal metastasis.

Material and methods

The immunostaining status of ADAMTS1, 8, 9, and 18 were investigated in formalin-fixed paraffin-embedded samples of 25 patients who underwent pancreaticoduodenectomy for an adenocarcinoma located at the head of the pancreas.

Results

In semi-quantitive grading pathologically, ADAMTS1, 8, 9, and 18 were found to be highly stained in all cancerous pancreas samples compared with normal pancreas. In addition, the immune positivity of ADAMTS1, 9, and 18 was found to be higher in metastatic lymph nodes than in non-metastatic lymph tissue. Tumour size was correlated with ADAMTS9 and 18 expressions in cancerous pancreas.

Conclusions

According to the data obtained from the study, we suggest that these four ADAMTSs may have significant roles in the tumorigenesis and nodal spread of pancreas adenocarcinoma.

Thrombotic thrombocytopenic purpura related to ADAMTS13 deficiency, and successful treatment in a chimpanzee (Pan troglodytes verus)

A 27-year-old male chimpanzee (Pan troglodytes verus) developed signs of thrombotic thrombocytopenic purpura (TTP). ADAMTS13 deficiency appeared to be the cause of disease. After treatment with high-dose prednisone, haematological values and clinical signs recovered. This is the first description of spontaneous TTP associated with ADAMTS13 deficiency in a non-human primate.

Von Willebrand Factor, ADAMTS13, and the Risk of Mortality

Objective—

Von Willebrand Factor (VWF) is a plasma protein that plays a major role in platelet adhesion and aggregation. Large VWF multimers are cleaved into smaller, less coagulant forms by the metalloprotease ADAMTS13 (A Disintegrin And Metalloprotease with ThromboSpondin motif repeats 13). Previous studies have shown that high VWF and low ADAMTS13 levels are associated with cardiovascular disease, but whether these factors are associated with mortality is unclear. Our aim is to establish the association between VWF antigen (VWF:Ag) levels, ADAMTS13 activity, and mortality.

Approach and Results—

We included 6130 participants of the Rotterdam study, a population-based cohort study among individuals aged ≥55 years. We determined the association between ADAMTS13 activity, VWF:Ag levels, and all-cause and cardiovascular mortality by Cox proportional hazard regression analysis. During a median follow-up time of 11.3 years and a total of 90 635 person years, 1868 of the 6130 individuals died (30.5%), of whom 442 (23.7%) died because of cardiovascular disease. In individuals with low ADAMTS13 activity, the risk of cardiovascular mortality (hazard ratio, 1.46; 95% confidence interval, 1.09–1.96) was higher than that in individuals with high ADAMTS13 activity. The risk of cardiovascular mortality (hazard ratio, 1.29; 95% confidence interval 0.98–1.70) was higher in individuals with the highest VWF:Ag levels than in those with the lowest levels. In individuals with both low ADAMTS13 activity and high VWF:Ag levels, the risk of cardiovascular mortality was even higher (hazard ratio, 1.73 95% confidence interval, 1.28–2.35).

Conclusions—

In this large prospective cohort study, ADAMTS13 activity and VWF:Ag levels are both associated with an increased risk of all-cause and cardiovascular mortality.

Blood biomarkers associated with neurological deterioration in patients with acute penetrating artery territory infarction: A multicenter prospective observational study

Background and purpose

Neurological deterioration in acute penetrating artery territory infarction is unpredictable and associated with unfavorable clinical outcomes. The aim of this prospective study was to clarify the cause of neurological worsening and predict clinical outcomes using blood biomarkers.

Methods

Eight Japanese stroke centers participated. Blood samples were obtained within 24 h (the first sampling) and on day 7 in hospital (the second sampling) in patients with penetrating artery territory infarction, arriving within two days of stroke onset. Symptomatic worsening was defined as a minimum increase of one point on the National Institutes of Health Stroke Scale. Poor outcome was defined as a modified Rankin Scale score of ≥3 at 90 days after ictus.

Results

Of the 89 patients, 25 (28%) had symptomatic worsening, and 25 (28%) had a poor outcome. Although tumor necrosis factor-alpha, high-sensitivity C-reactive protein levels were significantly increased in both groups at the second sampling, soluble lectin-like oxidized low-density lipoprotein receptor-1, CD40 ligand, and pro-adrenomedullin levels were significantly increased and ADAMTS13 activity was decreased in symptomatic worsening patients ( p < 0.05 for all). After multivariate adjustment, a low number of CD34+ cells at the first sampling was an independent predictor of poor outcome (odds ratio, 0.20; 95% confidence interval, 0.04–0.74, p = 0.011, per 1 cell/µl increase).

Conclusions

Blood biomarkers associated with atherosclerotic processes seem to be an indication for symptomatic worsening, and the number of CD34+ cells may help to predict three-month functional outcome in patients with penetrating artery territory infarction.

Low ADAMTS-13 activity and the risk of coronary heart disease - a prospective cohort study: the Rotterdam Study

Essentials An association between ADAMTS-13 and coronary heart disease (CHD) has been suggested. 5688 participants ≥ 55 years from the Rotterdam Study without a history of CHD were included. Over a median follow-up time of 9.7 years, 456 individuals suffered from CHD. Low ADAMTS-13 activity was associated with an increased CHD risk.

SUMMARY

Background The metalloprotease ADAMTS-13 cleaves high-molecular-weight von Willebrand factor multimers into smaller, less procoagulant forms. Low ADAMTS-13 activity is associated with an increased risk of ischemic stroke but its pathogenic role in coronary heart disease (CHD) is unclear. Objectives We aimed to determine the association between ADAMTS-13 activity and the risk of CHD in a large prospective population-based cohort study. Methods A total of 5688 participants of the Rotterdam Study, a population-based cohort study involving individuals aged ≥ 55 years without a history of CHD, were included. ADAMTS-13 activity was measured by the FRETS-VWF73 assay and VWF:Ag levels by ELISA. We assessed the association between ADAMTS-13 activity, VWF:Ag levels and CHD using Cox proportional hazard regression analysis, adjusting for cardiovascular risk factors. Results Over a median follow-up time of 9.7 years, 456 individuals suffered from CHD. A low ADAMTS-13 activity (quartile 1) was associated with an increased CHD risk (HR 1.42, 95% CI 1.07-1.89) compared with the reference highest quartile. Conclusions Low ADAMTS-13 activity is associated with an increased risk of CHD in the elderly, independently of VWF and established cardiovascular risk factors.

Human neutrophil peptides and complement factor Bb in pathogenesis of acquired thrombotic thrombocytopenic purpura

Acquired thrombotic thrombocytopenic purpura is primarily caused by the deficiency of plasma ADAMTS13 activity resulting from autoantibodies against ADAMTS13. However, ADAMTS13 deficiency alone is often not sufficient to cause acute thrombotic thrombocytopenic purpura. Infections or systemic inflammation may precede acute bursts of the disease, but the underlying mechanisms are not fully understood. Herein, 52 patients with acquired autoimmune thrombotic thrombocytopenic purpura and 30 blood donor controls were recruited for the study. The plasma levels of human neutrophil peptides 1-3 and complement activation fragments (i.e. Bb, iC3b, C4d, and sC5b-9) were determined by enzyme-linked immunosorbent assays. Univariate analyses were performed to determine the correlation between each biomarker and clinical outcomes. We found that the plasma levels of human neutrophil peptides 1-3 and Bb in patients with acute thrombotic thrombocytopenic purpura were significantly higher than those in the control (P<0.0001). The plasma levels of HNP1-3 correlated with the levels of plasma complement fragment Bb (rho=0.48, P=0.0004) and serum lactate dehydrogenase (rho=0.28, P=0.04); in addition, the plasma levels of Bb correlated with iC3b (rho=0.55, P<0.0001), sC5b-9 (rho=0.63, P<0.0001), serum creatinine (rho=0.42, p=0.0011), and lactate dehydrogenase (rho=0.40, P=0.0034), respectively. Moreover, the plasma levels of iC3b and sC5b-9 were correlated (rho=0.72, P<0.0001), despite no statistically significant difference of the two markers between thrombotic thrombocytopenic purpura patients and the control. We conclude that innate immunity, i.e. neutrophil and complement activation via the alternative pathway, may play a role in the pathogenesis of acute autoimmune thrombotic thrombocytopenic purpura, and a therapy targeted at these pathways may be considered in a subset of these patients.

Low ADAMTS13 activity is associated with an increased risk of ischemic stroke

ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin motif repeats 13) has antithrombotic properties because it cleaves von Willebrand factor (VWF) in smaller, less active multimers. The aim of our study was to investigate prospectively the association between ADAMTS13 activity and ischemic stroke. We included 5941 individuals ≥55 years without a history of stroke or transient ischemic attack (TIA) of the Rotterdam Study, a population-based cohort study. ADAMTS13 activity was measured at inclusion with the FRETS-VWF73 assay and VWF antigen (VWF:Ag) levels by enzyme-linked immunosorbent assay. We assessed the association among ADAMTS13 activity, VWF:Ag levels, and ischemic stroke by Cox proportional hazard analysis. The added value of ADAMTS13 activity above the traditional risk factors for ischemic stroke risk prediction was examined by the C-statistic and the net reclassification improvement index (NRI). All individuals were followed for incident stroke or TIA. Over a median follow-up time of 10.7 years (56,403 total person-years), 461 participants had a stroke, 306 of which were ischemic. After adjustment for cardiovascular risk factors, individuals with ADAMTS13 activity in the lowest quartile had a higher risk of ischemic stroke (absolute risk, 7.3%) than did those in the reference highest quartile (absolute risk, 3.8%; hazard ratio, 1.65; 95% confidence interval [CI], 1.16-2.32). Adding ADAMTS13 to the model in prediction of ischemic stroke, increased the C-statistic by 0.013 (P = .003) and provided 0.058 (95% CI, -0.002 to 0.119) NRI. Low ADAMTS13 activity is associated with the risk of ischemic stroke and improves the accuracy of risk predictions for ischemic stroke beyond traditional risk factors.

Genetic variants in the ADAMTS13 and SUPT3H genes are associated with ADAMTS13 activity

We identify rs41314453 as the strongest genetic predictor of ADAMTS13 activity, associated with a decrease of >20%. We present evidence of further independent associations with a common variant in SUPT3H, as well as 5 variants at the ADAMTS13 locus.

Transfusion of Blood and Blood Products

In transfusion medicine, several blood products can be prepared and used as replacement therapy; however, four of these products are more commonly used in general practice: RBCs, fresh frozen plasma (FFP), platelets and cryoprecipitate. RBC transfusions are mainly administered to improve tissue oxygenation in cases of anaemia or acute blood loss due to trauma or surgery. FFP, platelets and cryoprecipitate are used for the prevention and treatment of bleeding.

Pregnancy complications in acquired thrombotic thrombocytopenic purpura: a case-control study

Background

Pregnant women with a history of acquired thrombotic thrombocytopenic purpura (TTP) are considered at risk for disease recurrence and might be at risk for miscarriage, similar to other autoimmune disorders. However, the exact entity of these risks and their causes are unknown. The aim of this study was to evaluate risk factors associated with adverse pregnancy outcome, in terms of both gravidic TTP and miscarriage, in women affected by previous acquired TTP.

Methods

We conducted a nested case–control study in women with a history of acquired TTP enrolled in the Milan TTP registry from 1994 to October 2012, with strict inclusion criteria to reduce referral and selection bias.

Results

Fifteen out of 254 women with acquired TTP were included, namely four cases with gravidic TTP, five with miscarriage, and six controls with uncomplicated pregnancy. In the cases, ADAMTS13 activity levels in the first trimester were moderately-to-severely reduced (median levels <3% in gravidic TTP and median levels 20% [range 14-40%] in the women with miscarriage) and anti-ADAMTS13 antibodies were invariably present, while in the control group ADAMTS13 activity levels were normal (median 90%, range 40-129%), with absence of detectable anti-ADAMTS13 antibodies. Reduced levels of ADAMTS13 activity (<25%) in the first trimester were associated with an over 2.9-fold increased risk for gravidic TTP and with an over 1.2-fold increased risk for miscarriage (lower boundary of the confidence interval of the odds ratio). In addition, the presence of anti-ADAMTS13 antibodies during pregnancy was associated with an over 6.6-fold increased risk for gravidic TTP and with an over 4.1-fold increased risk for miscarriage.

Conclusions

ADAMTS13 activity evaluation and detection of anti-ADAMTS13 antibody could help to predict the risk of complications in pregnant women with a history of acquired TTP.

Von Willebrand factor-cleaving protease activity in thrombotic microangiopathy: first report from iran

BACKGROUND

Thrombotic microangiopathy (TMA) is a rare but devastating small vessels disorder that is characterized by intravascular platelet thrombi, thrombocytopenia, and various degrees of organ ischemia and anemia, which is due to erythrocyte fragmentation in microcirculation.

OBJECTIVES

The Aim of this study was to determine the von Willebrand factor-cleaving protease (ADAMTS13) activity during the acute phase of TMA. We also investigated inhibiting antibodies against ADAMTS13 in these patients.

PATIENTS AND METHODS

In a collaborative work with Mario-Negro institute of pharmacological research in Bergamo-Italy, we registered the clinical and laboratory data, collected the serum samples, and transferred the samples to the laboratories. Serum samples were taken before the start of plasmapheresis or at least 15 days after the final exchange.

RESULTS

We recruited 40 patients (14 males and 26 females) with the mean age of 46.12 ± 17.26 years. The mean activity of ADAMTS13 was 34.58% ± 21.83%. Two patients had inhibitory antibodies against ADAMTS13 with profound deficiency of ADAMTS13 activity (< 6%). Infectious diseases were the most common underlying condition, followed by systemic lupus erythematous.

CONCLUSIONS

Majority of patients had an underlying condition and had various ADAMTS13 activity. The presence of inhibiting antibodies and accompanied complete deficiency of ADAMTS13 activity is an indicator of severity.

Von Willebrand factor and ADAMTS13 in arterial thrombosis: a systematic review and meta-analysis

Von Willebrand Factor (VWF) plays an important role in hemostasis by mediating platelet adhesion and aggregation. Ultralarge VWF multimers are cleaved by ADAMTS13 in smaller, less procoagulant forms. An association between high VWF levels and cardiovascular disease has frequently been reported, and more recently also an association has been observed between low ADAMTS13 levels and arterial thrombosis. We reviewed the current literature and performed meta-analyses on the relationship between both VWF and ADAMTS13 with arterial thrombosis. Most studies showed an association between high VWF levels and arterial thrombosis. It remains unclear whether ADAMTS13 is a causal independent risk factor because the association between low ADAMTS13 and arterial thrombosis is so far only shown in case-control studies. Prospective studies are awaited. A causal role for ADAMTS13 is supported by mice studies of cerebral infarction where the infusion of recombinant human ADAMTS13 reduced the infarct size.

Association between reversible cerebral vasoconstriction syndrome and thrombotic thrombocytopenic purpura

BACKGROUND

Reversible cerebrovascular constriction syndrome (RCVS) presents with thunderclap headache and ischemic neurological deficits due to focal vasoconstrictions in major intracranial arteries. Reversibility of focal vasoconstrictions is the hallmark of RCVS. The commonest conditions associated with RCVS are a post-partum state and administration of vasoactive agents.

METHODS

We describe a series of 3 cases of thrombotic thrombocytopenic purpura (TTP) who presented with thunderclap headache and focal neurological deficits.

RESULTS

Vascular imaging revealed focal areas of constrictions in multiple intracranial arteries. All cases were treated with plasmapheresis and serial transcranial Doppler (TCD) and magnetic resonance angiography revealed resolution of cerebral vasoconstriction, accompanied by clinical recovery.

CONCLUSION

RCVS should be considered in patients with TTP who presented with thunderclap headache. TCD is an important tool for monitoring the course of cerebral vasoconstriction in TTP.

Thrombotic thrombocytopenic purpura and the atypical hemolytic uremic syndrome: an update

Since the last review in 2007 of thrombotic thrombocytopenic purpura (TTP) and microangiopathic hemolytic anemia in the Clinics, further understanding of the nature of TTP and atypical hemolytic uremic syndrome (aHUS) has led to increasing use of rituximab in the treatment of TTP and the approval in 2011 of eculizumab for the treatment of aHUS. With this new armamentarium, distinction of aHUS from TTP has become more critical than ever. This article updates the new knowledge, highlights the difference between aHUS and TTP, and presents a scheme for their diagnosis and management.

ADAMTS13 content in plasma-derived factor VIII/von Willebrand factor concentrates

Thrombotic thrombocytopenic purpura (TTP) is a microangiopathy syndrome caused by a congenital or acquired deficiency of ADAMTS13, a plasma metalloprotease that cleaves von Willebrand factor (VWF) and thus prevents the formation of platelet-rich thrombi in the microcirculation. TTP can be fatal if not appropriately and timely treated with the infusion of fresh frozen plasma (FFP) or exchange plasmapheresis, that reverse the process of microangiopathy by removing anti-ADAMTS13 autoantibodies and replacing functional ADAMTS13. The treatment of TTP with FFP is not free from risks and must be administered in hospitals or clinics, owing to the substantial amount of plasma volume infused or exchanged and the frequent need of catheter application. Moreover, most FFPs are not subjected to treatments to remove or inactivate blood-borne infectious agents. A number of recent reports indicate that certain plasma-derived VWF-factor VIII (FVIII) concentrates are clinically effective in the treatment of congenital TTP. In this study, we measured ADAMTS13 levels in various plasma-derived VWF-FVIII concentrates, showing that Koate(®) -DVI (Grifols), contained relatively high amounts of ADAMTS13 and that Alphanate(®) (Grifols) was the closest other product in terms of protease content. Koate(®) -DVI contains, on average (five lots tested), 0.091 ± 0.007 Units of ADAMTS13 activity per IU of FVIII. On the basis of this analysis and other reports of VWF-FVIII concentrate utilization in congenital TTP, potential dosing, and future clinical developments are discussed.

Advantages and limits of ADAMTS13 testing in the prognostic assessment of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare but severe disease characterized by mechanical hemolytic anemia and consumptive thrombocytopenia leading to disseminated microvascular thrombosis that causes signs and symptoms of organ ischemia and functional damage. After the elucidation of the pathophysiology of TTP, thanks to the demonstration of the congenital or acquired (autoimmune) plasma deficiency of the von Willebrand factor cleaving metalloprotease A Disintegrin And Metalloprotease with ThromboSpondin 1 repeats (ADAMTS13), a number of laboratory assays for measuring ADAMTS13 and related autoantibodies have been developed. Current knowledge on the diagnostic and prognostic value of ADAMTS13 and anti-ADAMTS13 assays is summarized in this review.

Local elongation of endothelial cell-anchored von Willebrand factor strings precedes ADAMTS13 protein-mediated proteolysis

Platelet-decorated von Willebrand factor (VWF) strings anchored to the endothelial surface are rapidly cleaved by ADAMTS13. Individual VWF string characteristics such as number, location, and auxiliary features of the ADAMTS13 cleavage sites were explored here using imaging and computing software. By following changes in VWF string length, we demonstrated that VWF strings are cleaved multiple times, successively shortening string length in the function of time and generating fragments ranging in size from 5 to over 100 μm. These are larger than generally observed in normal plasma, indicating that further proteolysis takes place in circulation. Interestingly, in 89% of all cleavage events, VWF strings elongate precisely at the cleavage site before ADAMTS13 proteolysis. These local elongations are a general characteristic of VWF strings, independent of the presence of ADAMTS13. Furthermore, large elongations, ranging in size from 1.4 to 40 μm, occur at different sites in space and time. In conclusion, ADAMTS13-mediated proteolysis of VWF strings under flow is preceded by large elongations of the string at the cleavage site. These elongations may lead to the simultaneous exposure of many exosites, thereby facilitating ADAMTS13-mediated cleavage.

Microangiopathic disorders in pregnancy

Microangiopathic disorders present with thrombocytopenia, hemolytic anemia, and multiorgan damage. In pregnancy, these disorders present a challenge both diagnostically and therapeutically, with widely overlapping clinical scenarios and disparate treatments. Although rare, a clear understanding of these diseases is important because devastating maternal and fetal outcomes may ensue if there is misdiagnosis and improper treatment. Microangiopathic disorders presenting in pregnancy are thus best assessed and treated by both obstetric and hematology teams. As a better understanding of the pathophysiology underlying each of the disease processes is gained, new diagnostic testing and therapies will be available, which will lead to improved outcomes.

Pathogenesis, diagnosis and management of paraneoplastic glomerulonephritis

Paraneoplastic glomerulonephritis is a rare complication of malignancy that is frequently mistaken for idiopathic glomerulonephritis. Failure to recognize paraneoplastic glomerulonephritis can subject patients to ineffective and potentially harmful therapy. The pathology of paraneoplastic glomerulonephritis varies between different types of malignancies. This Review discusses the association of glomerulonephritis with both solid tumors and hematological malignancies. The pathogenetic mechanisms of many glomerular lesions seem to relate to altered immune responses in the presence of a malignancy. Studies in the Buffalo/Mna rat model of spontaneous thymoma and nephrotic syndrome indicate that polarization of the immune response toward a T-helper-2 (T(H)2) profile has an important role in the development of thymoma-associated glomerular lesions. Furthermore, overexpression of the T(H)2 cytokine interleukin 13 in rats induces minimal change disease. Such findings from experimental studies might facilitate the identification of biomarkers that can distinguish paraneoplastic glomerulonephritis from idiopathic and other secondary glomerulonephritides. This Review describes potential pathogenetic mechanisms for paraneoplastic glomerulonephritides associated with different malignancies and highlights the need for a multidisciplinary approach to the management of patients with paraneoplastic glomerulonephritis.

Thrombotic microangiopathy in systemic lupus erythematosus: a cohort study in North Taiwan

OBJECTIVES

Thrombotic microangiopathy (TMA) co-existing with SLE is rarely reported. This study aimed to investigate the triggering factors, clinical features and outcomes of SLE patients with TMA in Northern Taiwan.

METHODS

Twenty-five TMA cases out of 2461 SLE patients admitted to Taipei Veterans General Hospital, between 2000 and 2010, were enrolled.

RESULTS

When TMA occurred, 16 (64.0%) patients had infection; 22 (88.0%) were in an active disease state with a SLEDAI score >10. Among the infection group, 13 (81.3%) had an increase in the SLEDAI score of ≥ 4. We found that older age (≥ 50 years), low platelets (≤ 20,000/nm(3)), presence of infection, acute renal failure (ARF) or four or more TMA features were independent risk factors for persistent haematological abnormalities (P < 0.05); older age (≥ 50 years) and a high reticulocyte index (>2%) were the risk factors for persistent renal function impairment (P < 0.05). The overall mortality rate was 52.0% (13 out of 25); older age (≥ 40 years), low complement value, presence of infection (P < 0.001), two or more infection sources, ARF and four or more TMA features were the statistically significant factors contributing to a higher mortality rate. Patients receiving plasma exchange seven times or more had a significantly higher rate of improvement in renal function and haematological abnormalities.

CONCLUSIONS

Our study showed that infection was one of the major triggers for the flare-up of SLE disease activity and occurrence of TMA in SLE. Infection is also a strong risk factor for outcome in SLE patients with TMA. Plasma exchange can be considered as an adjuvant treatment modality.

The distal carboxyterminal domains of murine ADAMTS13 influence proteolysis of platelet-decorated VWF strings in vivo

BACKGROUND

The multidomain metalloprotease ADAMTS13 regulates the size of von Willebrand factor (VWF) multimers upon their release from endothelial cells. How the different domains in ADAMTS13 control VWF proteolysis in vivo remains largely unidentified.

METHODS

Seven C-terminally truncated murine ADAMTS13 (mADAMTS13) mutants were constructed and characterized in vitro. Their ability to cleave VWF strings in vivo was studied in the ADAMTS13(-/-) mouse.

RESULTS

Murine MDTCS (devoid of T2-8 and CUB domains) retained full enzyme activity in vitro towards FRETS-VWF73 and the C-terminal T6-8 (del(T6-CUB)) and CUB domains (delCUB) are dispensable under these assay conditions. In addition, mADAMTS13 fragments without the spacer domain (MDT and M) had reduced catalytic efficiencies. Our results hence indicate that similar domains in murine and human ADAMTS13 are required for activity in vitro, supporting the use of mouse models to study ADAMTS13 function in vivo. Interestingly, using intravital microscopy we show that removal of the CUB domains abolishes proteolysis of platelet-decorated VWF strings in vivo. In addition, whereas MDTCS is fully active in vivo, partial (del(T6-CUB)) or complete (delCUB) addition of the T2-8 domains gradually attenuates its activity.

CONCLUSIONS

Our data demonstrate that the ADAMTS13 CUB and T2-8 domains influence proteolysis of platelet-decorated VWF strings in vivo.

Thrombotic thrombocytopenic purpura: A single - Centre experience

We aimed to describe the characteristics, treatment regime, and 6-month all-cause mortality of thrombotic thrombocytopenic purpura (TTP) patients treated with total plasma exchange in the our clinic. Thirteen patients were included in the study. Mortality rates of TTP have improved over the last three decades but they are still too high according to modern therapy expectations. Etiology directed treatment should be added to total plasma exchange in secondary TTP cases. Based on TTPs' immunologic etiology, immune modulator and immune suppressor agents have been applied together with total plasma exchange, but mostly in anecdotal case reports or with questionable responses.