What's new in the diagnosis and pathophysiology of thrombotic thrombocytopenic purpura

Association of thrombotic microangiopathy with interferon therapy for hepatitis B: a case report

BACKGROUND

Thrombotic microangiopathy is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ injury. The pathological features include vascular damage that is manifested by arteriolar and capillary thrombosis with characteristic abnormalities in the endothelium and vessel wall. Thrombocytopenia is one of the common adverse effects of interferon therapy. However, a more serious but rare side effect is thrombotic microangiopathy.

CASE PRESENTATION

We report the case of a 36-year-old Asian male patient with clinical manifestations of hypertension, blurred vision, acute renal failure, thrombocytopenia, and thrombotic microangiopathy. Renal biopsy showed interstitial edema with fibrosis, arteriolar thickening with vitreous changes, and epithelial podocytes segmental fusion. Immunofluorescence microscopy showed C3(+), Ig A(+) deposition in the mesangial region, which was pathologically consistent with thrombotic microangiopathy renal injury and Ig A deposition. The patient had a history of hepatitis B virus infection for more than 5 years. Lamivudine was used in the past, but the injection of long-acting interferon combined with tenofovir alafenamide fumarate was used since 2018. The comprehensive clinical investigation and laboratory examination diagnosed the condition as thrombotic microangiopathy kidney injury caused by interferon. After stopping interferon in his treatment, the patient's renal function partially recovered after three consecutive therapeutic plasma exchange treatments and follow-up treatment without immunosuppressant. The renal function of the patient remained stable.

CONCLUSIONS

This report indicates that interferon can induce thrombotic microangiopathy with acute renal injury, which can progress to chronic renal insufficiency.

Risk factors of death or chronic renal replacement therapy requirements in patients with thrombotic microangiopathies without ADAMTS-13 deficiency

Thrombotic microangiopathy (TMA), characterized by microangiopathic hemolytic anemia, thrombocytopenia, and multisystem organ dysfunction, is a life-threatening disease. Patients with TMA who do not exhibit a severe ADAMTS-13 deficiency (defined as a disintegrin-like and metalloprotease with thrombospondin type 1 motif no. 13 activity ≥10%: TMA-13n) continue to experience elevated mortality rates. This study explores the prognostic indicators for augmented mortality risk or necessitating chronic renal replacement therapy (composite outcome: CO) in TMA-13n patients. We included 42 TMA-13n patients from January 2008 to May 2018. Median age of 41 years and 60% were female. At presentation, 62% required dialysis, and 57% warranted intensive care unit admission. CO was observed in 45% of patients, including a 9-patient mortality subset. Multivariate logistic regression revealed three independent prognostic factors for CO: early administration of eculizumab (median time from hospitalization to eculizumab initiation: 5 days, range 0-19 days; odds ratio [OR], 0.14; 95% confidence interval [CI], 0.02-0.94), presence of neuroradiological lesions (OR, 6.67; 95% CI, 1.12-39.80), and a PLASMIC score ≤4 (OR, 7.39; 95% CI, 1.18-46.11). In conclusion, TMA-13n patients exhibit a heightened risk of CO in the presence of low PLASMIC scores and neuroradiological lesions, while early eculizumab therapy was the only protective factor.

Immune Thrombotic Thrombocytopenic Purpura: Pathophysiology, Diagnosis, Therapy and Open Issues

Immune thrombotic thrombocytopenic purpura (iTTP) is a life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia, and ischemic end-organ injury due to microvascular platelet-rich thrombi. iTTP pathophysiology is based on a severe ADAMTS13 deficiency, the specific von Willebrand factor (vWF)-cleaving protease, due to anti-ADAMTS13 autoantibodies. Early diagnosis and treatment reduce the mortality. Frontline therapy includes daily plasma exchange (PEX) with fresh frozen plasma replacement and immunosuppression with corticosteroids. Caplacizumab has recently been added to frontline therapy. Caplacizumab is a nanobody that binds to the A1 domain of vWF, blocking the interaction of ultra-large vWF multimers with the platelet and thereby preventing the formation of platelet-rich thrombi. Caplacizumab reduces mortality due to ischemic events, refractoriness, and exacerbations after PEX discontinuation. Until now, the criteria for response to treatment mainly took into account the normalization of platelet count and discontinuation of PEX; with the use of caplacizumab leading to rapid normalization of platelet count, it has been necessary to redefine the response criteria, taking into account also the underlying autoimmune disease. Monitoring of ADAMTS13 activity is important to identify cases with a low value of activity (<10IU/L), requiring the optimization of immunosuppressive therapy with the addition of Rituximab. Rituximab is effective in patients with refractory disease or relapsing disease. Currently, the use of Rituximab has expanded, both in frontline treatment and during follow-up, as a pre-emptive approach. Some patients do not achieve ADAMTS13 remission following the acute phase despite steroids and rituximab treatment, requiring an individualized immunosuppressive approach to prevent clinical relapse. In iTTP, there is an increased risk of venous thrombotic events (VTEs) as well as arterial thrombotic events, and most occur after platelet normalization. Until now, there has been no consensus on the use of pharmacological thromboprophylaxis in patients on caplacizumab because the drug is known to increase bleeding risk.

Cost-effectiveness of rapid vs in-house vs send-out ADAMTS13 testing for immune thrombotic thrombocytopenic purpura

ABSTRACT

While awaiting confirmatory results, empiric therapy for patients suspected to have immune thrombotic thrombocytopenic purpura (iTTP) provides benefits and also accrues risks and costs. Rapid assays for ADAMTS13 may be able to avoid the cost and risk exposure associated with empiric treatment. We conducted, to our knowledge, the first cost-effectiveness evaluation of testing strategies with rapid vs traditional ADAMTS13 assays in patients with intermediate- to high-risk PLASMIC scores, with and without caplacizumab use. We built a Markov cohort simulation with 4 clinical base-case analyses: (1) intermediate-risk PLASMIC score with caplacizumab; (2) intermediate-risk PLASMIC score without caplacizumab; (3) high-risk PLASMIC score with caplacizumab; and (4) high-risk PLASMIC score without caplacizumab. Each of these evaluated 3 testing strategies: (1) rapid assay (<1-hour turnaround); (2) in-house fluorescence resonance energy transfer (FRET)-based assay (24-hour turnaround); and (3) send-out FRET-based assay (72-hour turnaround). The primary outcome was the incremental net monetary benefit reported over a 3-day time horizon and across accepted willingness-to-pay thresholds in US dollars per quality-adjusted life-year (QALY). While accruing the same amount of QALYs, the rapid assay strategy saved up to $46 820 (95% CI, $41 961-$52 486) per patient tested. No parameter variation changed the outcome. In probabilistic sensitivity analyses, the rapid assay strategy was favored in 100% (3 base cases and scenario analyses) and 99% (1 base-case and scenario analysis) across 100 000 Monte Carlo iterations within each. Rapid ADAMTS13 testing for patients with intermediate- or high-risk PLASMIC scores yields significant per patient cost savings, achieved by reducing the costs associated with unnecessary therapeutic plasma exchange and caplacizumab therapy in patients without iTTP.

Adult-onset Still's disease with concurrent thrombotic microangiopathy: Observations from pooled analysis for an uncommon finding

BACKGROUND

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder that is characterized by quotidian fevers, arthritis, and an evanescent rash. Occurrence of concurrent thrombotic microangiopathy (TMA) in AOSD is rare. The treatment aspects of TMA in AOSD are actively being debated.

METHODS

Medline search using MeSH terms and snowballing yielded a total of 29 articles with co-occurrence of AOSD and thrombotic thrombocytopenic purpura (TTP) including our own. Pooled data were synthesized for descriptive analysis.

RESULTS

Median age was 35 years with a majority of females (68.96%). A majority of these studies/patients were either Asian (34.48%) or Caucasian (31.03%). Concurrent TMA at the time of AOSD diagnosis was seen in 65.51% patients. Only 3/29 patients had ADAMTS13 level less than 10%, consistent with TTP and 3/29 were diagnosed with hemolytic uremic syndrome (HUS). The remainder were diagnosed clinically. Complication rate was high, and 15/29 (51.72%) patients died or had permanent neurological/renal/vision/gangrenous complications. Median and mean ferritin peak was observed to be higher (7458 and 12 349, respectively) in patients who either died/had partial remission, compared to those who had complete response (3257 and 10 899, respectively), p = .829.

CONCLUSIONS

A majority of patients with AOSD-associated TMA either died or had permanent complications. TMA was diagnosed alongside AOSD in 65% patients, while the rest developed TMA during the course of their disease. Blurred vision may precede TMA and could help risk-stratify high-risk AOSD patients clinically. Glycosylated ferritin remains low several weeks to months after disease remission and may be used to monitor severity of disease process. Further studies are necessary to confirm the existing vascular endothelial growth factor hypothesis in AOSD-associated TMA.

Caplacizumab for immune thrombotic thrombocytopenic purpura: real-world multicenter data

Given the limited real-world data of caplacizumab, our multicenter real-world study was designed to assess the safety and efficacy of caplacizumab in immune thrombotic thrombocytopenic pupura (iTTP), compared to historic controls. We have studied 70 patients: 23 in the caplacizumab and 47 in the historic control group. Plasma exchange was applied in all episodes except for two patients that denied plasma exchange. Rituximab as first-line treatment was more common in the caplacizumab group compared to historic control. Caplacizumab (10 mg daily) was given at a median on day 7 (1-43) from initial diagnosis for 32 (6-47) dosages. In the caplacizumab group, a median of 12 (8-23) patients required plasma exchange sessions versus 14 (6-32) in the control group. Caplacizumab administration did not produce any grade 3 complications or major hemorrhagic events. After a median of 19.0 (2.6-320) months since the iTTP diagnosis, 5 deaths occurred (4 in the control group and 1 in the caplacizumab group, p = 0.310). Caplacizumab patients achieved early platelet normalization and ADAMTS13 activity normalization at the end of treatment. Relapse was observed only in 2/23 (9%) caplacizumab patients, compared to 29/47 (62%) historic controls (p < 0.001). Overall, caplacizumab is safe and effective in treating iTTP, including cases refractory to plasma exchange, re-administration, and cases without previous plasma exchange treatment. No major hemorrhagic events were observed. Cessation of dosing guided by ADAMTS13 has ensured a low relapse rate.

A validation and modification of PLASMIC score by adjusting the criteria of mean corpuscular volume and international normalized ratio

BACKGROUND

The PLASMIC score was developed for distinguishing thrombotic thrombocytopenic purpura (TTP) from other types of thrombotic microangiopathy. However, two components of the PLASMIC score, mean corpuscular volume (MCV) and international normalized ratio (INR), showed non-significant differences between TTP and non-TTP patients in previous validations. Here, we validate the PLASMIC score and aim to modify it by adjusting the criteria of MCV and INR.

MATERIALS AND METHODS

A retrospective validation of suspected TTP patients was performed by reviewing electronic medical records from two medical centers in Taiwan. The performance of different modified types of the PLASMIC score was carried out.

RESULTS

Among 50 patients included in the final analysis, 12 were diagnosed with TTP based on deficiency of ADAMTS13 activity and clinical judgement. When stratified by high (score ≥ 6) and low-intermediate risk (score < 6), the positive predictive value (PPV) of the PLASMIC score to predict TTP was 0.45 (95% confidence interval [CI]: 0.29-0.61). The area under curve (AUC) was 0.70 (95% CI: 0.56-0.82). When adjusting the criteria of the PLASMIC score from MCV < 90 fL to MCV ≥ 90 fL, the PPV increased to 0.57 (95% CI: 0.37-0.75). The AUC was 0.75 (95% CI: 0.61-0.87). When adjusting the INR from >1.5 to >1.1, the PPV increased to 0.56 (95% CI: 0.39-0.71). The AUC was 0.81 (95% CI: 0.68-0.90).

CONCLUSION

MCV ≥ 90 fL and/or INR > 1.1 might be suitable modifications for PLASMIC score but should be validated in a larger sample size.

Congenital Thrombotic Thrombocytopenic Purpura: A Rare Cause of Recurrent Thrombocytopenia and Anemia

Congenital thrombotic thrombocytopenic purpura (cTTP) is a rare autosomal recessive microangiopathic disorder caused by inherited mutations in the ADAMTS13 gene. cTTP treatment involves infusing ADAMTS13-rich blood products like fresh frozen plasma (FFP) to replenish levels and prevent disease relapses. Alternative therapies like recombinant ADAMTS13, plasma-derived Factor VIII, or caplacizumab may be used for patients unable to tolerate FFP. We present a case of a five-month-old girl who had recurrent episodes of anemia and thrombocytopenia. She was diagnosed with cTTP based on the presence of low ADAMTS13 activity and the identification of a homozygous likely pathogenic variant in the ADAMTS13 gene. After receiving regular transfusions of FFP, our patient improved significantly and has been asymptomatic for 18 months with no transfusion complications.

Global Health Resource Utilization and Cost-Effectiveness of Therapeutics and Diagnostics in Immune Thrombotic Thrombocytopenic Purpura (TTP)

In this review, we examine the current landscape of health resource utilization and cost-effectiveness data in the care of patient populations with immune thrombotic thrombocytopenic purpura. We focus on the therapeutic (therapeutic plasma exchange, glucocorticoids, rituximab, caplacizumab) and diagnostic (ADAMTS13 assay) health technologies employed in the care of patients with this rare disease. Health resource utilization and cost-effectiveness data are limited to the high-income country context. Measurement of TTP-specific utility weights in the high-income country context and collection of health resource utilization data in the low- and middle-income country settings would enable an evaluation of country-specific quality-adjusted life expectancy and cost-effectiveness of these therapeutic and diagnostic health technologies. This quantification of value is one way to mitigate cost concerns where they exist.

Spanish registry of thrombotic thrombocytopenic purpura (REPTT): Data evidence and new developments

Immuno Thrombotic thrombocytopenic purpura (iTTP) is a rare and potentially fatal disorder characterized by systemic microvascular thrombosis because of a severe deficiency of ADAMTS13. It is difficult to generate knowledge about TTP because of its low incidence and the lack of clinical trials. Most of the evidence on diagnosis, treatment, and prognosis has been generated from real-world data registries. In 2004, the Spanish Apheresis Group (GEA) implemented the Spanish registry of TTP (REPTT) with 438 patients suffering 684 acute episodes in 53 hospitals up to January 2022. REPTT has studied several aspects of TTP in Spain. The iTTP incidence in Spain our country is 2.67 (95 % CI 1.90-3.45) and the prevalence is 21.44 (95 % CI % 19.10-23.73) patients per million inhabitants. The refractoriness incidence is 4.8 % and exacerbation incidence was 8.4 %, with a median of follow-up of 131.5 months (IQR: 14-178 months). In a 2018 review, the mortality in the first episode due to TTP was 7.8 %. We have also found that de novo episodes require fewer PEX procedures than relapses. Since June 2023, REPTT will involve Spain and Portugal, with a recommended sampling protocol and new variables to improve the neurological, vascular and quality of life evaluation of these patients. The main strength of this project will be the involvement of a combined population of more than 57 million inhabitants, which implies an annual incidence of close to 180 acute episodes per year. This will allow us to provide better answers to questions like treatment efficacy, associated morbidity and mortality, and the possible neurocognitive and cardiac sequelae.

Thrombotic thrombocytopenic purpura with neurological impairment: A Review

The last 2 decades have witnessed considerable advances in our understanding of thrombotic thrombocytopenic purpura (TTP). However, there is still some ambiguity regarding the precise nature of this disease, especially with respect to nervous system involvement and the correct nomenclature. This article seeks to summarize the clinical manifestations of TTP and the associated diseases. We describe TTP complicated with cerebrovascular disease, spinal cord injury, posterior reversible encephalopathy syndrome (PRES), anxious-depressive symptoms, and cognitive decline. TTP with spinal cord injury is rarely reported. For better clarity, we discuss the case of a 57-year-old woman who was diagnosed with neuromyelitis optica spectrum disease (NMOSD) with atypical TTP. The concurrent occurrence of NMOSD and TTP in this patient is consistent with the characteristics of acquired autoimmunity. We highlight the importance of early recognition of TTP in patients with atypical presentation who may not have the expected clinical or laboratory findings. This is particularly important in TTP patients with other concomitant autoimmune diseases or age-related comorbid conditions.

Refractory Thrombotic Thrombocytopenic Purpura to Therapeutic Plasma Exchange

Thrombotic thrombocytopenic purpura (TTP) is a rare, potentially fatal hematologic disorder characterized by microangiopathic hemolytic anemia, thrombocytopenia, and varying signs of visceral ischemia secondary to microvascular thrombosis. TTP is caused by a severe deficiency of ADAMTS13, a protease enzyme responsible for cleaving von Willebrand-factor (vWF) multimers. First-line therapy with plasmapheresis has increased survival rates immensely; however, there are few reported cases that are refractory to standardized treatment. We describe two cases of refractory TTP successfully managed with the addition of caplacizumab, an anti-von Willebrand factor immunoglobulin fragment that inhibits the interaction of vWF multimers with platelets.

A Case of Paediatric Anti-Glomerular Basement Membrane Disease Associated with Thrombotic Thrombocytopenic Purpura

Anti-GBM disease is a rare vasculitis that causes rapid progressive glomerulonephritis and pulmonary haemorrhage. It is usually an adult diagnosis with isolated paediatric cases reported. Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy mainly affecting adults that causes multiorgan ischaemia, microangiopathic haemolytic anaemia, and thrombocytopenia. We present the first paediatric case of concurrent anti-GBM disease and TTP. A 14-year-old boy presented with acute kidney failure and severe pulmonary haemorrhage due to anti-GBM disease, confirmed on auto-antibody testing. There was thrombocytopenia and moderately low ADAMTS13 activity suggestive of TTP. The renal prognosis was poor with a need for dialysis. He was severely unwell with pulmonary haemorrhages requiring the use of extracorporeal membrane oxygenation (ECMO). His disease was treated with corticosteroids, plasma exchange (PEX), rituximab, and cyclophosphamide, resulting in remission. Anti-GBM disease is rare in children but should be considered in those presenting with acute kidney injury, particularly where there has been exposure to pulmonary irritants. An aggressive presentation warrants aggressive treatment with methylprednisolone, PEX, and cyclophosphamide. Rituximab may benefit patients that have concurrent TTP. TTP may exacerbate pulmonary disease, but complete respiratory recovery is possible. Disease relapse is rare in the paediatric age group, and these patients are candidates for kidney transplantation.

Risk factors of trauma-induced thrombotic microangiopathy-like syndrome: A retrospective analysis

Patients with trauma may develop thrombocytopenia. We encountered cases wherein patients experienced symptoms resembling thrombotic microangiopathies (TMAs) following severe trauma. As the condition of these patients did not meet the diagnostic criteria of thrombotic thrombocytopenic purpura and there was no mention of trauma among the several causes of TMAs, it was termed as "trauma-induced thrombotic microangiopathy-like syndrome" (t-TMAS). In this study, we aimed to analyze the risk factors that may affect the incidence of t-TMAS in patients with severe trauma. This retrospective study was conducted in the trauma intensive care unit at the Kyungpook National University Hospital between January 2018 and December 2019. The medical records of 1164 of the 1392 enrolled participants were analyzed. To assess the risk factors of t-TMAS, we analyzed age, sex, mechanism of trauma, abbreviated injury scale (AIS) score, injury severity score (ISS), hematological examination, and red blood cell volume transfused in 24 hours. Among the 1164 patients, 20 (1.7%) were diagnosed with t-TMAS. The univariate analysis revealed higher age, ISS, and myoglobin, lactate, creatine kinase-myocardial band (on admission), creatine phosphokinase, lactate dehydrogenase (LDH), and lactate (day 2) levels in the t-TMAS group than in the non-t-TMAS group. The red blood cell volume transfused in 24 hours was higher in the t-TMAS group than in the non-t-TMAS group. t-TMAS was more common in patients with injuries in the chest, abdomen, and pelvis (AIS score ≥3) than in those with head injuries (AIS score ≥3) alone. The higher the sum of AIS scores of the chest, abdomen, and pelvis injuries, the higher the incidence of t-TMAS. Multivariate analysis revealed age, ISS, and LDH level (day 2) to be independent predictors of t-TMAS. Trauma surgeons should consider the possibility of t-TMAS if thrombocytopenia persists without any evidence of bleeding, particularly among older patients with multiple severe torso injuries who have high LDH levels on day 2. Early diagnosis and treatment of t-TMAS could improve patients' prognosis.

COVID-19 Vaccines and Autoimmune Hematologic Disorders

Worldwide vaccination against SARS-CoV-2 has allowed the detection of hematologic autoimmune complications. Adverse events (AEs) of this nature had been previously observed in association with other vaccines. The underlying mechanisms are not totally understood, although mimicry between viral and self-antigens plays a relevant role. It is important to remark that, although the incidence of these AEs is extremely low, their evolution may lead to life-threatening scenarios if treatment is not readily initiated. Hematologic autoimmune AEs have been associated with both mRNA and adenoviral vector-based SARS-CoV-2 vaccines. The main reported entities are secondary immune thrombocytopenia, immune thrombotic thrombocytopenic purpura, autoimmune hemolytic anemia, Evans syndrome, and a newly described disorder, so-called vaccine-induced immune thrombotic thrombocytopenia (VITT). The hallmark of VITT is the presence of anti-platelet factor 4 autoantibodies able to trigger platelet activation. Patients with VITT present with thrombocytopenia and may develop thrombosis in unusual locations such as cerebral beds. The management of hematologic autoimmune AEs does not differ significantly from that of these disorders in a non-vaccine context, thus addressing autoantibody production and bleeding/thromboembolic risk. This means that clinicians must be aware of their distinctive signs in order to diagnose them and initiate treatment as soon as possible.

Co-existence of Thrombotic Thrombocytopenic Purpura and Megaloblastic Anaemia: A Case-Based Review

Introduction

Thrombotic thrombocytopenic purpura is a rare and fatal thrombotic microangiopathy characterised by a pentad of microangiopathic haemolytic anaemia, thrombocytopenia, renal abnormalities, neurological abnormalities, and fever. Due to ineffective erythropoiesis, vitamin-B12 deficiency may rarely present as haemolytic anaemia.

Case report

We report a case of a 42-year-old vegetarian female presenting as vitamin B12 deficiency anaemia found to have concomitant TTP, responding to plasmapheresis, corticosteroids, and rituximab therapy.

Discussion

In this case of vitamin B12 deficiency with co-existent TTP, we hypothesise vitamin B12 deficiency as a contributory or precipitating factor for TTP. We reviewed similar cases in the literature to support this hypothesis. Timely detection of TTP and the initiation of treatment is of utmost importance as TTP has a high mortality when left untreated. The possible relationship with Vitamin B12 deficiency needs further exploration.

COVID19 epidemic outbreak: operating rooms scheduling, specialty teams timetabling and emergency patients' assignment using the robust optimization approach

The health care system is characterized by limited resources, including the physical facilities as well as skilled human resources. Due to the extensive fixed cost of medical facilities and the high specialization required by the medical staff, the problem of resource scarcity in a health care supply chain is much more acute than in other industries. In the pandemic of the Coronavirus, where medical services are the most important services in communities, and protective and preventive guidelines impose new restrictions on the system, the issue of resource allocation will be more complicated and significantly affect the efficiency of health care systems. In this paper, the problem of activating the operating rooms in hospitals, assigning active operating rooms to the COVID-19 and non-COVID-19 patients, assigning specialty teams to the operating rooms and assigning the elective and emergency patients to the specialty teams, and scheduling their operations is studied by considering the new constraints of protective and preventive guidelines of the Coronavirus. To address these issues, a mixed-integer mathematical programming model is proposed. Moreover, to consider the uncertainty in the surgery duration of elective and emergency patients, the stochastic robust optimization approach is utilized. The proposed model is applied for the planning of operating rooms in the cardiovascular department of a hospital in Iran, and the results highlight the role of proper management in supplying sufficient medical resources effectively to respond to patients and scheduled surgical team to overcome the pressure on hospital resources and medical staff results from pandemic conditions.

Application of PLASMIC Score in Risk Prediction of Thrombotic Thrombocytopenic Purpura: Real-World Experience From a Tertiary Medical Center in Taiwan

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder caused by severe ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) deficiency (activity <10%). Urgent intervention based on the timely evaluation of ADAMTS13 level is crucial to guide optimal therapy. The recently developed PLASMIC score based on seven items allows the rapid identification of patients at high risk for TTP due to severe ADAMTS13 deficiency. This retrospective study included 31 hospitalized patients with suspicious thrombotic microangiopathy in National Cheng Kung University Hospital from December 2016 to July 2021. Data on ADAMTS13 activity and medical and laboratory information were retrieved from medical records. The PLASMIC score could be calculated in 24 of the 31 patients with available data, and the final cohort was stratified according to the 7-point PLASMIC score. All patients with high PLASMIC score (6-7) exhibited severe ADAMTS13 deficiency (activity ≤10%). One patient with a brain tumor and a PLASMIC score of 6 did not have severe ADAMTS13 activity of ≤10%. The patients in the intermediate- and low risk groups (PLASMIC scores of 5 and 0-4, respectively) exhibited ADAMTS13 activities of above 10%. Given the role of prompt diagnosis in the timely delivery of appropriate therapy, these findings confirm and strengthen the predictive value of the PLASMIC score in patients at high risk for TTP due to severe ADAMTS13 deficiency.

Strong association between insufficient plasma exchange and fatal outcomes in Japanese patients with immune-mediated thrombotic thrombocytopenic purpura

Plasma exchange (PEX) using fresh frozen plasma has considerably reduced the mortality rate in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP). However, some patients still do not survive even with treatment, but little information is available regarding which treatment these patients received. This study was conducted to obtain this information in 240 patients who met the current iTTP diagnostic criteria and completed at least 30 days of follow-up except for deceased cases. These patients were divided into three groups: survivors (n = 195), TTP-related deaths (n = 32), and other cause of death (n = 13). In the TTP-related death group, 26 of 32 patients experienced sudden death, mostly following radical hypotension and bradycardia. The median follow-up time after admission was 5.0 days, and the median number of PEX sessions was 2.5. Nine patients underwent autopsy and had cardiac microvascular thrombi in arterioles. Levels of lactate dehydrogenase, total bilirubin, serum creatinine, and D-dimer were significantly higher in the TTP-related death group than in the survivors group. Frequent PEX (> 20 sessions) was not associated with TTP-related death. In the acute phase of iTTP, patients with substantial organ damage caused by microthrombi have a greater mortality risk, even after just a few PEX sessions.

Making the Correct Diagnosis in Thrombotic Microangiopathy: A Narrative Review

Purpose of review:

Thrombotic microangiopathy (TMA) is suspected in patients presenting with thrombocytopenia and evidence of a microangiopathic hemolytic anemia. Patients with TMA can be critically ill, so rapid and accurate identification of the underlying etiology is essential. Due to better insights into pathophysiology and causes of TMA, we can now categorize TMAs as thrombotic thrombocytopenic purpura, postinfectious (mainly Shiga toxin-producing Escherichia coli–induced) hemolytic uremic syndrome (HUS), TMA associated with a coexisting condition, or atypical HUS (aHUS). We recognized an unmet need in the medical community to guide the timely and accurate identification of TMA, the selection of tests to clarify its etiology, and the sequence of steps to initiate treatment.

Sources of information:

Key published studies relevant to the identification, classification, and treatment of TMAs in children or adults. These studies were obtained through literature searches conducted with PubMed or based on the prior knowledge of the authors.

Methods:

This review is the result of a consultation process that reflects the consensus of experts from Canada, the United States, and the United Arab Emirates. The members represent individuals who are clinicians, researchers, and teachers in pediatric and adult medicine from the fields of hematology, nephrology, and laboratory medicine. Authors, through an iterative review process identified and synthesized information from relevant published studies.

Key findings:

Thrombotic thrombocytopenic purpura occurs in the setting of insufficient activity of the von Willebrand factor protease known as ADAMTS13. Shiga toxin-producing Escherichia coli–induced hemolytic uremic syndrome, also known as “typical” HUS, is caused by gastrointestinal infections with bacteria that produce Shiga toxin (initially called verocytotoxin). A variety of clinical conditions or drug exposures can trigger TMA. Finally, aHUS occurs in the setting of inherited or acquired abnormalities in the alternative complement pathway leading to dysregulated complement activation, often following a triggering event such as an infection. It is possible to break the process of etiological diagnosis of TMA into 2 distinct steps. The first covers the initial presentation and diagnostic workup, including the processes of identifying the presence of TMA, appropriate initial tests and referrals, and empiric treatments when appropriate. The second step involves confirming the etiological diagnosis and moving to definitive treatment. For many forms of TMA, the ultimate response to therapies and the outcome of the patient depends on the rapid and accurate identification of the presence of TMA and then a standardized approach to seeking the etiological diagnosis. We present a structured approach to identifying the presence of TMA and steps to identifying the etiology including standardized lab panels. We emphasize the importance of early consultation with appropriate specialists in hematology and nephrology, as well as identification of whether the patient requires plasma exchange. Clinicians should consider appropriate empiric therapies while following the steps we have recommended toward definitive etiologic diagnosis and management of the TMA.

Limitations:

The evidence base for our recommendations consists of small clinical studies, case reports, and case series. They are generally not controlled or randomized and do not lend themselves to a stricter guideline-based methodology or a Grading of Recommendations Assessment, Development and Evaluation (GRADE)-based approach.

Frequent recurrence of pregnancy-triggered congenital thrombotic thrombocytopenic purpura: A rare case report

Thrombotic thrombocytopenic purpura (TTP) in adults is rare thrombotic microangiopathy (TMA), which is closely related to the lack of specific proteases of von Willebrand factor (vWF) multimers. It is currently believed that both congenital TTP (cTTP) and acquired TTP (aTTP) can induce acute attack through pregnancy. We report a case of a 24-year-old woman who was diagnosed as TTP during early pregnancy. A novel mutation was detected: c.3667G>T (p.E1223*). She responded well to plasma therapy during pregnancy and had a child by cesarean section at 32 weeks. TTP is still recurrent in postpartum patients. The plasma transfusion was effective, but caused a severe transfusion reaction. Cyclosporine was administered with the consent of the patient. This case showed cyclosporine-A (CSA) had a positive effect on ADAMTS13 activity. At 11-months follow-up, the patient's blood cells and LDH status were stable and no symptom was seen. Our case suggests that the patient had an unreported genetic mutation that causes TTP, immune factors may be involved in the onset of cTTP during pregnancy, and the use of immunosuppressive agents is effective in preventing recurrence.

Analisi costo-efficacia di caplacizumab nel nuovo standard of care della porpora trombotica trombocitopenica immune in Italia

Objectives:

To evaluate the cost-effectiveness analysis (CEA) of caplacizumab in combination with plasmapheresis (PEX) and immunosuppression compared to PEX and immunosuppression in the treatment of acute episodes of iTTP.

Methods:

A Markov model was used to conduct the CEA from the perspective of the hospital, over a lifetime horizon. Clinical data derived from HERCULES trial and a systematic literature review. Economic input included direct costs only. Utility and disutility values were obtained from literature. Data on healthcare resources and costs were retrieved from HERCULES trial, literature, TTP guidelines and Italian tariffs. A sensitivity analysis was conducted. The cost-effectiveness probability was tested for several options of discount levels considering a suggested willingness to pay (WTP) threshold of € 60,000 in Italy.

Results:

The use of caplacizumab in combination with PEX and immunosuppression is associated with a positive difference in survival of 3.27 life years (24.53 vs 21.26) and in quality of life of 3.06 QALY (22.01 vs 18.96) when compared to PEX and immunosuppression. Caplacizumab leads to an ICER per life years of € 41,653 and an ICER per QALY of € 44,572. For the suggested WTP threshold, the probability of caplacizumab being cost-effective is 82.4% (no discount), 92.8% (15% discount), 95.3% (20% discount), 96.9% (25% discount) and 98.2% (30% discount).

Conclusions:

Caplacizumab in addition to PEX and immunosuppression is cost-effective, allowing the hospital to achieve greater efficiency in managing the burden of a life-threatening disease such as iTTP.

Identification of Biomarkers in Patients with Thrombotic Thrombocytopenic Purpura Presenting with Large and Small Ischemic Stroke

Background

Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder resulting in organ damage including ischemic strokes. We sought to characterize the neuroimaging patterns of stroke in a large cohort of patients with immune-mediated TTP (iTTP) and determined their associations with clinical and laboratory parameters and outcomes.

Methods

We analyzed the Alabama TTP Registry who had laboratory confirmation of acute iTTP. We reviewed the neuroimaging patterns of those with ischemic stroke on MRI, clinical information, and laboratory results. Small ischemic strokes were ≤20 mm in their maximum diameter in the axial plane. Large ischemic strokes were >20 mm. Student t test, Mann-Whitney U test, and χ² test were all used for data analysis.

Results

Of 108 iTTP patients, 21 had ischemic stroke on neuroimaging. The median platelet count in these patients was 12 × 10⁹/L (interquartile range, IQR, 8.8–21 × 10⁹/L), plasma ADAMTS13 activity 1.8 U/dL (IQR 0–4.5 U/dL), and the mean plasma level of anti-ADAMTS13 IgG was 6,595.8 U/mL (SD 3,448.9 U/mL). Comparison between patients with large ischemic strokes (n = 10) and small ischemic strokes (n = 11) revealed that patients with small stroke were older (p = 0.043) and had higher plasma levels of citrullinated histone 3 (p = 0.006) and histone/DNA complex (p = 0.014) than those with large strokes. There were no significant differences between 2 stroke groups in mortality or exacerbation.

Conclusions

iTTP patients can present with large ischemic strokes and are usually younger. Further research should be performed in assessing different etiologies of iTTP-associated stroke based on neutrophil extracellular trap formation biomarkers (e.g., histone markers) seen in small ischemic stroke.

Spontaneous recovery in a patient with acquired thrombotic thrombocytopenic purpura (TTP): observation of a 'subclinical' TTP state

OBJECTIVES

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy that can have high mortality rates without prompt treatment. Standard treatment is urgent plasma exchange (PLEX), which leads to disease remission in the vast majority of patients. Deficiency of ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) alone is not sufficient to cause the clinical manifestations characteristic of TTP. We present a case of acquired TTP, where spontaneous recovery was observed prior to initiation of any TTP-specific therapy.

CLINICAL PRESENTATION

A 73-year-old asymptomatic female presented with new-onset mild haemolytic anaemia and thrombocytopenia. Further testing revealed a significantly reduced ADAMTS13 activity level and an ADAMTS13 inhibitor, concerning for acquired TTP. On reassessment, the patient's haematologic parameters had been corrected prior to initiation of therapy. During subsequent follow-up three months later, she developed acute worsening thrombocytopenia indicative of relapsed, acute TTP. The patient was then successfully managed with PLEX and rituximab and achieved a sustained remission.

DISCUSSION AND CONCLUSION

TTP is a haematologic emergency that requires urgent therapy to reduce morbidity and mortality. However, it is well documented that individuals with hereditary TTP and a proportion with acquired TTP in clinical remission can have low or nearly absent ADAMTS13 activity levels without evidence of microangiopathic haemolytic anaemia (MAHA) or thrombotic manifestations. Our patient represents a unique case of confirmed ADAMTS13 deficiency due to a documented inhibitor, leading to mild haemolytic anaemia and thrombocytopenia both of which recovered spontaneously. We propose that this scenario could represent a 'subclinical' TTP state that precedes the development of clinically significant disease.

A multicenter laboratory assessment of a new automated chemiluminescent assay for ADAMTS13 activity

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially fatal disorder caused by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency. Prompt identification/exclusion of TTP can thus be facilitated by rapid ADAMTS13 testing. The most commonly utilized (enzyme-linked immunosorbent assay [ELISA]-based) assay takes several hours to perform and so does not generally permit rapid testing.

OBJECTIVES

To evaluate the utility of a new automated test for ADAMTS13 activity, the HemosIL AcuStar ADAMTS13 Activity assay, based on chemiluminescence and able to be performed on an ACL AcuStar instrument within 33 minutes.

PATIENTS/METHODS

This multicenter (n = 8) assessment included testing of more than 700 test samples, with similar numbers of prospective (n = 348) and retrospective (n = 385) samples. The main comparator was the Technozym ADAMTS13 Activity ELISA. We also assessed comparative performance for detection of ADAMTS13 inhibitors using a Bethesda assay.

RESULTS

Overall, the chemiluminescent assay yielded similar results to the comparator ELISA, albeit with slight negative bias. ADAMTS13 inhibitor detection was also comparable, albeit with slight positive bias with the AcuStar assay. Assay precision was similar with both assays, and we also verified assay normal reference ranges.

CONCLUSIONS

The HemosIL AcuStar ADAMTS13 Activity assay provided results rapidly, which were largely comparable with the Technozym ADAMTS13 Activity ELISA assay, albeit lower on average. Conversely, inhibitor levels tended to be identified at a higher level on average. Thus, the HemosIL AcuStar ADAMTS13 Activity assay provides a fast and accurate means to quantitate plasma levels of ADAMTS13 for TTP/ADAMTS13 identification/exclusion, and potentially also for other applications.

[Endothelial dysfunction in thrombotic thrombocytopenic purpura: therapeutic perspectives]

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

Therapeutic Plasma Exchange in the Critically Ill Patient: Technology and Indications

Therapeutic plasma exchange (TPE) is frequently the most common Apheresis Medicine technique used for extracorporeal therapy of a wide variety of renal, neurological, hematological, and other clinical indications. Many of these clinical indications require intensive care during critical illness. Conventional TPE uses one of two main technical methods to achieve the goal of removing known disease mediators from the plasma: using centrifugal forces to separate and remove components of blood, or a membrane filtration method that separates plasma from the cellular components of blood. The following review discusses the basic principles of TPE, the technological aspects, and relevant clinical scenarios encountered in the intensive care unit, including relevant guidelines and recommendations from the American Society for Apheresis.

Multicentric evaluation of the new HemosIL Acustar® chemiluminescence ADAMTS13 activity assay

INTRODUCTION

Thrombotic thrombocytopenic purpura (TTP) is a rare life-threatening thrombotic microangiopathy (TMA) characterized by the severe deficiency of ADAMTS13 activity (<10%). Rapid ADAMTS13 testing is crucial for early diagnosis and optimal management of TTP patients and other TMAs. The objective of this study was to retrospectively evaluate the performance of the recently commercialized HemosIL Acustar^® ADAMTS13 activity chemiluminescent immunoassay (Instrumentation Laboratory, Bedford, Massachusetts, United States) in a multicentric study between Spain and Portugal.

METHODS

A comparison method was performed to compare HemosIL Acustar^® with an in-house FRETS-VWF73 assay and two commercial ELISA assays: the TECHNOZYM^® ADAMTS13 Activity (Technoclone GmbH, Vienna, Austria) and the DG-EIA ADAMTS-13 Activity (Diagnostic Grifols, SA, Barcelona, Spain). A set of 241 frozen plasma samples with known ADAMST13 levels was used. Agreement between methods was assessed with focus on two cut-off ADAMTS13 activity values: <10% (the clinical accepted cut-off value to confirm TTP diagnosis) and <5%.

RESULTS

HemosIL AcuStar^® showed high agreement with the other methods in correctly classify patients with ADAMTS13 values below 10% (Kappa = 0.89) and even below 5% (Kappa = 0.94) with no false negatives and few false positives (5.40%; 95% CI: 2.20 to 8.60%). However, it also tended to underestimate ADAMTS13 levels, especially for the high assay range values (>40%) (absolute mean bias of 8.40% (95% CI: 6.53 to 10.42%)) when compared to other assays.

CONCLUSIONS

HemosIL AcuStar^® is highly sensitive to detect ADAMTS13 values below 10% and 5%. A large prospective validation study is needed to corroborate its utility in clinical practice.

Retinal involvement in acute thrombotic thrombocytopenic purpura: a case report

Background

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening hematological condition associated with deficiency in ADAMTS13. Ocular manifestations associated with TTP are uncommon.

Case presentation

Here we report a case where a 44 year old female patient with a history of symptomatic anemia and cotton wool appearance in retina during ophthalmological examination and subsequently, she was diagnosed to have TTP. The proper management with Therapeutic Plasma Exchange (TPE) and IV methylprednisolone improved the condition of the patient markedly.

Conclusion

It concludes that even though the presence of cotton wool appearance in retina is a nonspecific sign it needs to be properly evaluated as there can be underlying serious illnesses as in our patient. Cotton wool spots can be an early sign of underlying retinal compromise and it should be identified early.

Assessment and Monitoring of Patients with Immune-Mediated Thrombotic Thrombocytopenic Purpura (iTTP): Strategies to Improve Outcomes

Background

Acquired or immune-mediated TTP (iTTP) is a life-threatening thrombotic microangiopathy, characterized by the presence of microangiopathic hemolytic anemia and severe thrombocytopenia, and a variable degree of ischemic organ damage, related to a severe deficiency of ADAMTS13, which is a serine metalloprotease necessary for cleavage of large vWF multimers. There has been a dramatic decrease in mortality rates with the recognition of the pathophysiology of iTTP over the years. Although therapeutic plasma exchange (TPE) together with corticosteroids are the backbone of the upfront treatment of patients with iTTP with successful outcomes, patients may remain refractory and/or relapse following an initial response to this treatment.

Methods

We performed a review regarding the pathogenesis, diagnosis, treatment strategies, monitoring, and prognosis of iTTP.

Results

There are several new treatment strategies, which can be used among these patients, helping in improving outcomes of iTTP. Rituximab has been shown to be a safe and effective adjunct to TPE, especially in patients with refractory and/or relapse as well as it is increasingly used preemptively to prevent exacerbation or recurrence. Recently, caplacizumab, a nanobody targeting vWF, was approved as an addition to the current regimen of TPE and immunomodulation for patients of iTTP.

Conclusion

Specific predictors of relapse in patients in remission can be relevant for an optimal patient management. Different models including ADAMTS13 biomarkers can provide a new screening strategy to identify patients who may predict outcomes and the risk of relapse, benefit from preemptive therapy prior to relapse.

Thrombotic Thrombocytopenic Purpura Masquerading as Acute Ischemic Stroke

Thrombotic thrombocytopenic purpura (TTP) is a hematologic disorder that results in widespread clotting due to a deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) protease. This leads to excessive von Willebrand factor (VWF) protein-platelet multimers. Due to platelet consumption, platelet levels fall, resulting in thrombocytopenia. We examined a case of a 31-year-old female with no significant medical history who presented with expressive aphasia and paresthesias and was sent to the Emergency Department for a stroke workup. Imaging was negative for ischemic or hemorrhagic stroke; however, a complete blood count (CBC) was consistent with anemia and thrombocytopenia, resulting in a high suspicion for TTP. She was admitted to the intensive care unit and given fresh frozen plasma and packed red blood cells. Plasma exchange therapy was initiated, and her aphasia and paresthesias began to improve. The ADAMTS13 level returned at less than 5%, which prompted the initiation of rituximab therapy. During her 36-day hospital stay, she continued to receive daily steroids and plasma exchange and a total of four courses of rituximab. Her platelets steadily climbed, and she was discharged with instructions to follow up with outpatient hematology. TTP is a thrombotic microangiopathy that results in microscopic blood clots anywhere in the body, including the cerebral arteries. This results in the neurologic abnormalities that are often seen in TTP. Because TTP is a rare disease, treatment modalities are still scarce but include steroids, plasma exchange therapy, and rituximab. Novel therapies are on their way, one being caplacizumab, a monoclonal antibody that inhibits VWF from interaction with glycoprotein 1b. A concern highlighted by this case is the exclusion criteria for the administration of tissue plasminogen activator (TPA). As this patient presented with stroke symptoms and a negative head CT, TPA would have been administered had a CBC not returned showing evidence of TTP. This highlights the importance of strict adherence to the American Heart Association/American Stroke Association guidelines that include ensuring that the platelet count is >100,000 prior to the initiation of TPA.

Immune thrombotic thrombocytopenic purpura in older patients: prognosis and long-term survival

Older age is associated with increased mortality in immune thrombotic thrombocytopenic purpura (iTTP). Yet, data are scarce regarding iTTP occurring among older patients. To assess clinical features and long-term impact of iTTP on mortality in older patients (>60 years old), characteristics and prognoses of adult iTTP patients enrolled in the French Reference Center for Thrombotic Microangiopathies registry between 2000 and 2016 were described according to age (<60 years old or ≥60 years old). Long-term mortality of iTTP older survivors was compared with that of non-iTTP geriatric subjects. Comparing, respectively, older iTTP patients (N = 71) with younger patients (N = 340), time from hospital admission to diagnosis was longer (P < .0001); at diagnosis, delirium (P = .034), behavior impairment (P = .045), renal involvement (P < .0001), and elevated troponin level (P = .025) were more important whereas cytopenias were less profound (platelet count, 22 × 103/mm3 [9-57] vs 13 × 103/mm3 [9-21], respectively [P = .002]; hemoglobin level, 9 g/dL [8-11] vs 8 g/dL [7-10], respectively [P = .0007]). Short- and mid-term mortalities were higher (P < .0001) and increased for every 10 years of age range. Age ≥60 years, cardiac involvement, increased plasma creatinine level, and total plasma exchange volume were independently associated with 1-month mortality. Compared with a non-iTTP geriatric population, older survivors showed an increased long-term mortality (hazard ratio = 3.44; P < .001). In conclusion, older iTTP patients have atypical neurological presentation delaying the diagnosis. Age negatively impacts short-term but also long-term mortality.

Serum D-dimer as a potential new biomarker for prognosis in patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease, and its mortality rate is 10% to 20%. However, there are currently only a few markers to predict the prognosis in patients with TTP. We aimed to identify several clinical indices and laboratory parameters for predicting the prognosis of TTP at admission.A single-centre observational cohort study that included patients with TTP from the First Affiliated Hospital of Zhengzhou University in China was conducted from January 1, 2012 to November 30, 2018. The primary outcome was prognosis, including in-hospital mortality, major thromboembolic events, or failure to achieve remission at discharge. We used the random forest method to identify the best set of predictors.Eighty-seven patients with TTP were identified, of whom 12 died during the treatment. The total number of patients within-hospital mortality, major thromboembolic events, and failure to achieve remission at discharge was 58. The machine learning method showed that the D-dimer level was the strongest predictor of the primary outcome. Receiver operating characteristic (ROC) analysis demonstrated that the sensitivity and specificity of the D-dimer level alone for identifying high-risk patients were 78% and 81%, respectively, with an optimum diagnostic cut-off value of 770 ng/mL. The area under the ROC curve (AUC) was 0.80, and the 95% confidence interval (CI) was 0.70 to 0.90.This study found that the D-dimer level exhibited a good predictive ability for prognosis in patients with TTP. These findings may aid in the development of new and intensive treatment strategies to achieve remission among high-risk patients. However, external validation is necessary to confirm the generalizability of our approach across populations and treatment practices.

Efficacy and safety of open-label caplacizumab in patients with exacerbations of acquired thrombotic thrombocytopenic purpura in the HERCULES study

BACKGROUND

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare, life-threatening autoimmune thrombotic microangiopathy. Caplacizumab, an anti-von Willebrand Factor Nanobody® , is effective for treating aTTP episodes and is well tolerated.

OBJECTIVES AND METHODS

In the phase 3 HERCULES trial (NCT02553317), patients with aTTP received double-blind caplacizumab or placebo during daily therapeutic plasma exchange (TPE) and for ≥30 days thereafter. Patients who experienced an exacerbation while on blinded study drug treatment switched to receive open-label caplacizumab plus re-initiation of daily TPE. Exacerbations were defined as recurrence of disease occurring within 30 days after cessation of daily TPE.

RESULTS

Thirty-one patients (placebo, n = 28; caplacizumab, n = 3) had an exacerbation during double-blind treatment. Twenty-eight patients switched to open-label caplacizumab (placebo, n = 26; caplacizumab, n = 2); the three others discontinued upon exacerbation. Median time to platelet count response (≥150 × 109 /L) was 3.49 days upon receiving caplacizumab. There were no deaths. During open-label treatment, further exacerbation or a major thromboembolic event (vena cava thrombosis) was experienced by one patient (3.6%) each. Consistent with the double-blind phase, the most frequent treatment-emergent adverse events were catheter site hemorrhage (28.6%), headache (21.4%), and epistaxis (17.9%).

CONCLUSIONS

These results suggest that caplacizumab was efficacious and well tolerated in patients with aTTP who experienced a disease exacerbation during double-blind treatment in HERCULES.

Thrombotic thrombocytopenic purpura (TTP)-like syndrome in the HIV era

Background

The thrombotic microangiopathies (TMAs) is a heterogeneous group of relatively uncommon but serious disorders presenting with thrombocytopenia and microangiopathic haemolysis. Thrombotic thrombocytopenic purpura (TTP) is one of these microangiopathic processes. HIV infection is an acquired cause of TTP but the pathogenesis is poorly understood. HIV-associated TTP was previously described to be associated with advanced immunosuppression. The incidence of HIV-related TTP was expected to decline with access to anti-retroviral therapy (ART).

Methods

We undertook an observational study of patients with a diagnosis of TTP admitted to our hospital (CMJAH). The patient demographics, laboratory test results and treatment outcomes were recorded.

Results

Twenty-one patients were admitted with a diagnosis of TTP during the study period. All patients had schistocytes and severe thrombocytopaenia. The presenting symptoms were non-specific and renal dysfunction and neurological compromise were uncommon. 77% of the patients were HIV-infected and, in 7 patients, TTP was the index presentation. The remainder of the HIV infected patients were on ART and the majority were virologically suppressed. A significant female preponderance was present. Only 4 of the 21 patients tested HIV negative with a positive Coombs test in 2. All patients in this cohort received treatment with plasma exchange therapy for a median period of 12 days with a 96.5% survival rate. Neither the baseline laboratory features nor the degree of immunosuppression was predictive of the duration of therapy needed for remission.

Conclusion

HIV-related TTP is still a cause of morbidity and the clinical presentation is heterogeneous which may present a diagnostic challenge in the absence of sensitive biomarkers. Early treatment with plasma exchange is effective but expensive and invasive.

Pediatric thrombotic thrombocytopenic purpura

Child-onset thrombotic thrombocytopenic purpura (TTP) is a rare entity of thrombotic microangiopathy (TMA). The pathophysiology of the disease is based on a severe functional deficiency of ADAMTS13 (activity <10%), the specific von Willebrand factor (VWF)-cleavage protease. This deficiency may be either acquired (associated anti-ADAMTS13 autoantibodies) or congenital (resulting from biallelic mutations of ADAMTS13 gene). ADAMTS13 deficiency is responsible for the accumulation of high molecular weight multimers of VWF and the formation of platelet thrombi in the microcirculation. Consequently, microangiopathic hemolytic anemia and consumption thrombocytopenia are associated with organ ischemia. The differential diagnosis with other TMAs, autoimmune cytopenias or hematological malignancies may be challenging. The exploration of ADAMTS13 (activity, antibodies, antigen, ADAMTS13 gene) supports the diagnosis of TTP. The first-line treatment of the acute phase of TTP is based on plasmatherapy. In congenital TTP, patients with a chronic disease benefit from a prophylactic plasmatherapy. In autoimmune TTP, steroids and B-cells depleting therapies increasingly are used together with plasma exchange. Long-term follow-up including the monitoring of ADAMTS13 activity is mandatory. A severe decrease in ADAMTS13 activity (<10%) may predict relapses and preemptive B-cell depletion with rituximab can be used to prevent relapses.

The role of von Willebrand factor in thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The disease spectrum of TMA includes, amongst others, thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS). TTP is caused by defective cleavage of von Willebrand factor (VWF), whereas aHUS is caused by overshooting complement activation and subsequent endothelial cell (EC) injury. Despite their distinct pathophysiology, the clinical manifestation of TTP and aHUS consisting of microangiopathic haemolytic anaemia and thrombocytopenia is often similar and difficult to distinguish. Recent evidence hints at both a genetic and functional link between TTP and aHUS, especially between VWF and the complement system. There is novel in vitro evidence that complement activation not only results in VWF release from ECs, but that VWF also functions as a negative complement regulator, thus protecting the EC surface from ongoing complement attack. Although contrary to previous experimental work suggesting that complement can be activated on VWF multimers, there may be an explanation in vivo that rationalizes these apparently contradictory findings, whereby a system primarily meant to regulate becomes overwhelmed or pathologic in the disease state. The importance of unravelling these recent findings for our understanding of TMA pathology becomes even more evident considering that glomerular ECs express VWF in a heterogeneous pattern with an overall decreased expression level, thus potentially leaving the glomerular ECs vulnerable to complement-mediated injury. Taken together, these findings support the concept that TTP and aHUS represent two extreme ends of a TMA disease spectrum rather than isolated disease entities.

Clinical characteristics and outcomes of thrombotic microangiopathy in Malaysia

Background

Thrombotic microangiopathy (TMA) with non-deficient ADAMTS-13 (a disintegrin-like and metalloprotease with thrombospondin type 1 motif 13) outcome is unknown hence the survival analysis correlating with ADAMTS-13 activity is conducted in Malaysia.

Methods

This was a retrospective epidemiological study involving all cases of TMA from 2012–2016.

Results

We evaluated 243 patients with a median age of 34.2 years; 57.6% were female. Majority of the patients were Malay (62.5%), followed by Chinese (23.5%) and Indian (8.6%). The proportion of patients with thrombotic thrombocytopenic purpura (TTP) was 20.9%, 72.2% of which were acquired while 27.8% were congenital. Patients with ADAMTS-13 activity ≥5% had a four-fold higher odds of mortality compared to those with ADAMTS-13 activity <5% (odds ratio: 4.133, P=0.0425). The mortality rate was 22.6% (N=55). Most cases had secondary etiologies (42.5%), followed by acquired TTP (16.6%), atypical hemolytic uremic syndrome (HUS) or HUS (12.8%) and congenital TTP (6.4%). Patients with secondary TMA had inferior overall survival (P=0.0387). The secondary causes comprised systemic lupus erythematosus (30%), infection (29%), pregnancy (10%), transplant (8%), malignancy (6%), and drugs (3%). Transplant-associated TMA had the worst OS (P=0.0016) among the secondary causes. Plasma exchange, methylprednisolone and intravenous immunoglobulin were recorded as first-line treatments in 162 patients, while rituximab, bortezomib, vincristine, azathioprine, cyclophosphamide, cyclosporine, and tacrolimus were described in 78 patients as second-line treatment.

Conclusion

This study showed that TMA without ADAMTS-13 deficiency yielded inferior outcomes compared to TMA with severeADAMTS-13 deficiency, although this difference was not statistically significant.

Child-onset thrombotic thrombocytopenic purpura caused by p.R498C and p.G259PfsX133 mutations in ADAMTS13

INTRODUCTION

Patients suffering from congenital thrombotic thrombocytopenic purpura (cTTP) have a deficiency in ADAMTS13 due to mutations in their ADAMTS13 gene.

OBJECTIVE

The aim of this study was to determine ADAMTS13 parameters (activity, antigen, and mutations), to investigate if the propositus suffered from child-onset cTTP, and to study the in vitro effect of the ADAMTS13 mutations.

METHODS

ADAMTS13 activity and antigen were determined using the FRETS VWF73 assay and ELISA and ADAMTS13 mutations via sequencing of the exons. Mutant proteins were expressed in Chinese hamster ovary cells, and their expression was studied using fluorescence microscopy and ELISA. Molecular modeling was used to evaluate the effect of the mutations on ADAMTS13 structure and stability.

RESULTS

The propositus was diagnosed with cTTP at the age of 20. ADAMTS13 activity was below 10%, and 2 compound heterozygous mutations, the p.R498C point and the p.G259PfsX133 frameshift mutation, were identified. Expression of ADAMTS13 mutants revealed that the p.R498C and the p.G259PfsX133 mutation cause secretion and translation defects in vitro, respectively. Molecular modeling showed that the R498 intra-domain interactions are lacking in the p.R498C mutant, resulting in protein instability.

CONCLUSION

The ADAMTS13 mutations result in a severe ADAMTS13 deficiency explaining the patient's phenotype.

Dissecting the pathophysiology of immune thrombotic thrombocytopenic purpura: interplay between genes and environmental triggers

Although outstanding progress has been made in understanding the pathophysiology of thrombotic thrombocytopenic purpura (TTP), knowledge of the immunopathogenesis of the disease is only at an early stage. Anti-ADAMTS13 auto-antibodies were shown to block proteolysis of von Willebrand factor and/or induce ADAMTS13 clearance from the circulation. However, it still remains to identify which immune cells are involved in the production of anti-ADAMTS13 autoantibodies, and therefore account for the remarkable efficacy of the B-cell depleting agents in this disease. The mechanisms leading to the loss of tolerance of the immune system towards ADAMTS13 involve the predisposing genetic factors of the human leukocyte antigen class II locus DRB1*11 and DQB1*03 alleles as well as the protective allele DRB1*04, and modifying factors such as ethnicity, sex and obesity. Future studies have to identify why these identified genetic risk factors are also frequently to be found in the healthy population although the incidence of immune-mediated thrombotic thrombocytopenic purpura (iTTP) is extremely low. Moreover, the development of recombinant ADAMTS13 opens a new therapeutic era in the field. Interactions of recombinant ADAMTS13 with the immune system of iTTP patients will require intensive investigation, especially for its potential immunogenicity. Better understanding of iTTP immunopathogenesis should, therefore, provide a basis for the development of novel therapeutic approaches to restore immune tolerance towards ADAMTS13 and thereby better prevent refractoriness and relapses in patients with iTTP. In this review, we address these issues and the related challenges in this field.

Large vessel stroke as initial presentation of thrombotic thrombocytopenic purpura

A 67-year-old right-handed woman presented with dysarthria, left upper extremity weakness and right-sided neglect of 3 hours duration. Imaging of the brain revealed acute right middle cerebral artery stroke; however, tissue plasminogen activator could not be administered due to severe thrombocytopenia. A peripheral smear revealed schistocytes and the patient was treated empirically for thrombotic thrombocytopenic purpura (TTP) with therapeutic plasma exchange. An extensive workup revealed no embolic source or other cause for stroke, and a diagnosis of large vessel infarct secondary to TTP was made. After a prolonged hospital course, the patient had partial neurological recovery and was discharged to a rehabilitation facility. Although transient neurologic deficits due to small vessel occlusions are well described in TTP, large vessel infarct can occur as well. This diagnosis should be considered in patients presenting with concomitant stroke and thrombocytopenia, as untreated TTP is nearly always fatal.

Recent advances in understanding and management of acquired thrombocytopenia

There are numerous congenital and acquired causes of thrombocytopenia. Thrombocytopenia could be a result of decreased bone marrow production, increased consumption, increased destruction, splenic sequestration or a combination of these causes. In this review, we have focused on some of the serious acquired causes of thrombocytopenia. There have been some significant advances in our understanding of the pathophysiology, diagnostic testing, and treatment of immune thrombocytopenia, heparin-induced thrombocytopenia, thrombotic thrombocytopenic purpura, and atypical hemolytic uremic syndrome over the past five years. These advances have resulted in a significant decrease in mortality and morbidity of patients with these disorders. Despite these advances, we are still faced with numerous unanswered questions in the pathophysiology and management of these complex thrombocytopenic disorders.