Children and adults with thrombotic thrombocytopenic purpura associated with severe, acquired Adamts13 deficiency: comparison of incidence, demographic and clinical features

Main features of ischemic stroke in patients with acute immune-mediated thrombotic thrombocytopenic purpura

BACKGROUND

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a microangiopathy often characterized by acute neurological involvement including ischemic stroke (IS). The characteristics of IS in iTTP remain largely unknown.

AIMS

To evaluate the epidemiology, neuroimaging patterns and risk factors of IS in iTTP patients.

METHODS

We performed a cross-sectional study of patients enrolled in the Milan TTP Registry presenting with neurological signs/symptoms and underwent neuroimaging evaluation during their first acute iTTP episode.

RESULTS

Seventy-eight patients were enrolled, the majority of patients were female (72 %), with a median age of 46 years. Computed tomography (CT) was performed in all patients, and magnetic resonance (MRI) was performed in 38 % of patients. IS was confirmed in 18 out of 78 patients (23 %), most of whom (70 %) showed a non-lacunar pattern with multifocal involvement. In the subgroup of patients who had MRI (n = 30), IS was identified in 12 patients (40 %) and of them 6 (50 %) had a false negative result with CT scan. Patients with IS were slightly older than those without, whereas the prevalence of cardiovascular risk factors and iTTP-related parameters were comparable between the two groups.

CONCLUSION

23 % of patients presenting with neurological manifestations at their first acute TTP episode, showed brain IS. As expected, MRI showed higher sensitivity in detecting ischemic lesions underscoring its usefulness over CT in this setting. An unexpected prevalence of non-lacunar and multifocal stroke patterns warrants further investigation. Cardiovascular risk factors and iTTP-related clinical and laboratory parameters were similarly distributed in patients with and without IS.

Autoantibodies to ADAMTS13 in human immunodeficiency virus-associated thrombotic thrombocytopenic purpura

BACKGROUND AND OBJECTIVES

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal thrombotic microangiopathic disorder that can result from human immunodeficiency virus (HIV) infection. The pathogenesis involves a deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin motifs member 13) and the presence of anti-ADAMTS13 autoantibodies. However, there is insufficient information regarding the epitope specificity and reactivity of these autoantibodies. This study aimed to perform epitope-mapping analysis to provide novel insights into the specific epitopes on ADAMTS13 domains affected by autoantibodies.

MATERIALS AND METHODS

The study analysed 59 frozen citrate plasma samples from HIV-associated TTP patients in South Africa, measuring ADAMTS13 activity using Technozyme® ADAMTS13 activity test, total immunoglobulin (Ig) M and IgA antibodies levels using ELISA kit and purifying IgG antibodies using NAb™ Protein G spin columns. A synthetic ADAMTS13 peptide library was used for epitope mapping.

RESULTS

Overall, 90% of samples showed anti-ADAMTS13 IgG autoantibodies, with 64% of these antibodies being inhibitory, as revealed by mixing studies. Samples with ADAMTS13 antigen levels below 5% showed high anti-ADAMTS13 IgG autoantibody titres (≥50 IU/mL), whereas those with 5%-10% levels had low autoantibody titres (<50 IU/mL).The metalloprotease, cysteine-rich and spacer domains were 100% involved in binding anti-ADAMTS13 IgG antibodies, with 58% of samples containing antibodies binding to the C-terminal part of the ADAMTS13 disintegrin-like domain, indicating different pathogenic mechanisms.

CONCLUSION

The metalloprotease, cysteine-rich and spacer domains are the primary targets for anti-ADAMTS13 IgG autoantibodies in patients with HIV-associated TTP. These findings suggest potential effects on the proteolytic activity of ADAMTS13, highlighting the complex nature of the pathogenic mechanisms involved.

Caplacizumab as an add-on therapy in a 7-year-old girl with exacerbated immune-mediated thrombotic thrombocytopenic purpura, a case report and literature review

The cornerstone treatment for immune-mediated thrombotic thrombocytopenic purpura (iTTP) in children is a combination of therapeutic plasma exchange (TPE), corticosteroids, and rituximab. Caplacizumab is an anti-von Willebrand factor (VWF) NANOBODY molecule approved as a frontline therapy of iTTP for adults and children aged ≥12 years. Using caplacizumab in children aged <12 years remains a gray area based on recommendations but with no marketing authorization. We report the first case of a pediatric patient with iTTP successfully treated with a caplacizumab dose adjustment of 5 mg daily based on ADAMTS13 activity. We also review all published cases of iTTP in children aged <12 years treated with caplacizumab. This is a 7-year-old girl with clinical thrombotic microangiopathy, in the absence of diarrhea and kidney injury. With a French score of 2 and a PLASMIC score of 7 (high risk), the diagnosis of TTP was suspected and later confirmed by severely low ADAMTS13 activity (<5%). Immune-mediated TTP was distinguished from the congenital one due to the presence of a functional ADAMTS13 inhibitor. Daily TPE and intravenous corticosteroids were started on day 0 (D0). Rituximab was added on D4, and due to refractoriness under daily TPE, we considered off-label administration of caplacizumab from D12. A clinical answer, with a significant increase in the platelet count, was observed within 48 h. A complete ADAMTS13 recovery was reached on D62. No major adverse events were observed during the treatment. She was discharged from the hospital over 3 months ago with a platelet count still within normal ranges. In the literature, we identified a total of four case reports describing five iTTP patients aged <12 years treated with caplacizumab, with a 100% success and tolerability rate. These published data attest to the efficacy and safety of the systematic use of caplacizumab and rituximab as frontline therapy in pediatric iTTP under 12 years of age. Therefore, prospective data are needed to support commercial authorization of caplacizumab in this subpopulation. Close monitoring of ADAMTS13 activity is particularly of interest among children to limit the number of caplacizumab injections.

A Systematic Review of the Epidemiology and Disease Burden of Congenital and Immune-Mediated Thrombotic Thrombocytopenic Purpura

Congenital (cTTP) and immune-mediated (iTTP) thrombotic thrombocytopenic purpura are serious and rare clotting disorders resulting from a deficiency in the ADAMTS13 enzyme. A systematic review was conducted using the Ovid® MEDLINE & Embase databases to synthesize the epidemiology and burden of cTTP and iTTP worldwide (from January 1, 2010, to February 6, 2020, with an update that covered the period January 1, 2020-February 11, 2022). Outcomes of interest were incidence and prevalence of TTP, incidence of acute episodes, mortality, burden of illness (eg complications, healthcare utilization, patient-reported outcomes) and disease management. A total of 221 eligible observational studies were included. The incidence rate of acute episodes ranged from 0.19-0.35 person-years in adult patients with cTTP, and 1.81-3.93 per million persons per year for iTTP in the general population. Triggers of acute episodes were similar for cTTP and iTTP, with pregnancy and infection the most commonly observed. Exacerbation in patients with iTTP varied widely, ranging from 2.4-63.1%. All-cause mortality was observed in 0-13.4% of patients with cTTP, across studies and follow-up periods, and in 1.1% (median follow-up: 0.4 years) to 18.8% (1 year) of patients with iTTP during acute episodes. Cardiovascular, renal, and neurological disease were common complications. TTP also led to work disturbances, feelings of anxiety and depression, and general activity impairment. TTP treatment regimens used were generally reflective of current treatment guidelines. The evidence identified describes a high patient burden, highlighting the need for effective treatment regimens leading to improvements in outcomes. Considerable evidence gaps exist, particularly for disease epidemiology, patient-reported outcomes, costs of disease management, and associated healthcare resource utilization. This review may help increase disease awareness and highlights the need for additional real-world studies, particularly in geographical regions outside the United States and Western Europe.

ADAMTS13 in the New Era of TTP

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening, often immune-mediated disease that affects 2-13 persons per million per year. Hemolytic anemia, thrombocytopenia, and end-organ damage due to the formation of microthrombi are characteristic of TTP. ADAMTS13 is a disintegrin, metalloproteinase, cleaving protein of von Willebrand factor (VWF) that processes the VWF multimers to prevent them from interacting with platelets and, in turn, to microvascular thrombosis. Prompt diagnosis of TTP is critical yet challenging. Thrombotic microangiopathies have similar clinical presentation. Measurement of ADAMTS13 activity helps in the differential diagnosis. Less than 10% ADAMTS13 activity is indicative of TTP. Laboratory ADAMTS13 activity assays include incubating the test plasma with the substrate (full-length VWM multimers) and detection with direct or indirect measurement of the cleavage product. The purpose of this study is to examine the diagnostic potential, advantages, and weaknesses of the ADAMTS13 potency in TTP.

Efficacy and relative safety of caplacizumab in immune-mediated thrombotic thrombocytopenic purpura: a systematic review and meta-analysis

Immune-mediated thrombotic thrombocytopenia purpura (iTTP) is a rare microvascular disease characterized by severe disseminated microvascular thrombose-bleeding syndrome. Caplacizumab has been approved for the treatment of iTTP in combination with Plasma Exchange (PE) and immunosuppressive therapy, but its role in iTTP therapy remains uncertain. Therefore, we conducted a meta-analysis to investigate the safety and efficacy of caplacizumab for the treatment of patients with iTTP. We searched electronic databases (PubMed, Embase, Cochrane Library, and Scopus) and reference lists of relevant articles to find articles published from 2015 to 2022. The time to normalization of the platelet count of the group caplacizumab is shorter than the group placebo (SMD = -0.72; 95% CI -0.88 to -0.56; P  < 0.05). Caplacizumab reduced the incidence of mortality (OR = 0.41; 95% CI 0.18-0.92; P  < 0.05), exacerbations (OR = 0.10; 95% CI 0.05-0.18; P  < 0.05), and recurrence (OR = 0.17; 95% CI 0.06-0.50; P  < 0.05). However, the bleeding events in the caplacizumab group were higher than those in the placebo group, especially severe bleeding events. There was no difference in ADAMTS13 activity and thromboembolic events between the two groups. Our analysis indicated that caplacizumab is effective and well tolerated for the treatment of iTTP.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022362370.

Acquired Thrombotic Thrombocytopenic Purpura (TTP) Presenting With Synthetic Cannabinoid Use

Synthetic cannabinoids (SCs) have become commercially available throughout the United States as manufacturers circumvent regulations with labels stating "not for human consumption" with misleading advertisements, resulting in the consumption of products that are not safe or regulated. We present a case report of a middle-aged woman exhibiting altered mental status secondary to SC use who was found to have severe thrombocytopenia and hemolytic anemia. She was later confirmed to have thrombotic thrombocytopenic purpura (TTP) through ADAMTS13 testing. TTP is one of several platelet-related disorders presenting with findings of hemolytic anemia and thrombocytopenia. The presence of altered mental status is typically used as a symptomatic differentiator between hemolytic uremic syndrome, immune thrombocytopenic purpura, and TTP. SCs can cause superimposed altered mental status, which, in the setting of a concomitant platelet disorder, can complicate the standard workup and prolong the time to a final diagnosis. This case serves as an essential reminder that collecting detailed social history and promptly recognizing laboratory abnormalities is critical for early recognition of TTP, as the diagnosis is time-sensitive and delays in recognition can lead to significant morbidity and mortality.

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.

Hypertensive Emergency with Thrombotic Microangiopathy or TTP? A Case Series and Literature Review

Thrombotic microangiopathy (TMA) is associated with both hypertensive emergency and primary thrombocytopenia purpura (TTP). However, their clinical management is vastly different, with the latter necessitating urgent plasma exchange (PEX). We report two cases of hypertension-associated TMA (HTN-TMA) and a literature review of the clinical management of malignant hypertension. We suggest that in patients presenting with hypertensive emergency associated with TMA, a clinical diagnosis of HTN-TMA should be made, with emergent treatment to lower blood pressure started immediately. Although TTP is a differential diagnosis for TMA, PEX should not be started concurrently in the absence of other supporting evidence for TTP.

COVID-Induced Thrombotic Thrombocytopenic Purpura: A Case Report and Treatment-Focused Review

Thrombotic thrombocytopenic purpura (TTP) is a rare disease that is part of a vast spectrum of thrombotic microangiopathies (TMAs). Despite the rarity of TTP, clinicians must maintain a high suspicion of this disease. The condition is characterized by fever, low platelets, hemolytic anemia, renal abnormalities, and neurological dysfunction. However, all these symptoms are not necessarily present in all the patients. In this review, we describe a case of a 51-year-old female who presented to the emergency department (ED) with chief complaints of dizziness and lightheadedness, subsequently leading to a diagnosis of TTP, caused as a result of COVID-19. This review raises awareness so that there is early recognition of any hematological manifestations associated with COVID-19, reducing the morbidity and mortality associated with the disease. Due to the unpredictability of COVID-19 and its complications, robust research is needed to understand the mechanism and determine which patients are more at risk for adverse outcomes.

Real-World Data Analysis of Patients Affected by Immune-Mediated Thrombotic Thrombocytopenic Purpura in Italy

Background: The therapeutic management of immune-mediated thrombotic thrombocytopenic purpura (iTTP) has recently benefited from the introduction of caplacizumab, an agent directed at the inhibition of platelet aggregation. This real-world analysis investigated the epidemiology and the demographic and clinical characteristics of iTTP patients in Italy before and after caplacizumab introduction in 2020. Methods: Hospitalized adults with iTTP were included using the administrative databases of healthcare entities covering 17 million residents. Epidemiological estimates of iTTP considered the 3-year period before and after caplacizumab introduction. After stratification by treatment with or without caplacizumab, iTTP patients were characterized for their baseline features. Results: The annual incidence before and after 2020 was estimated in the range of 4.3-5.8 cases/million and 3.6-4.6 cases/million, respectively. From 2018 to 2022, 393 patients with iTTP were included, and 42 of them were treated with caplacizumab. Caplacizumab-treated patients showed better clinical outcomes, with tendentially shorter hospital stays and lower mortality rates (no treated patients died at either 1 month or 3 months after caplacizumab treatment initiation, compared to 10.5% and 11.1% mortality rates at 1 and 3 months, respectively, of the untreated ones). Conclusions: These findings may suggest that caplacizumab advent provided clinical and survival benefits for patients with iTTP.

HLA-DR-DQ associations, combined with PLASMIC score, are reliable predictors of acquired thrombotic thrombocytopenic purpura (aTTP) and aid in differentiating aTTP from other thrombotic microangiopathies

BACKGROUND

Thrombotic microangiopathies (TMA) are a group of disorders with overlapping clinical features that require urgent intervention. Treatment is based on the recognition of the TMA type, which is often challenging. The aim of this study was to identify specific HLA associations with different TMA types to aid rapid diagnosis and appropriate treatment, since the HLA assay can be completed within five hours.

METHODS

All 86 consecutive patients who presented to the University of Arkansas for Medical Sciences between May 2013 and January 2021 with a presumptive diagnosis of TMA were included in this study. HLA typing was performed and correlated with other clinical and laboratory studies.

RESULTS

In comparison with other types of TMA, patients with acquired thrombotic thrombocytopenic purpura (aTTP) showed increased frequencies of HLA-DRB1*11, HLA-DQB1*03:01/19, HLA-DRB1*08 and HLA-DRB3. Combining the presence of these HLA associations with a PLASMIC score of 6 or more achieved a higher positive predictive value (90%) for identifying aTTP than the PLASMIC score alone (69%). In comparison with other TMA types, patients with aTTP showed decreased frequencies of HLA-DRB4, HLA-DRB1*07, HLA-DQB1*02. The HLA-DRB1*07/DQB1*02 was not observed in any aTTP patients (negative predictive value: 100%), and thus the presence of this haplotype essentially rules out aTTP. Further, HLA-DRB1*11/DQB1*03:01/19 was absent in atypical hemolytic uremic syndrome patients.

CONCLUSION

HLA alleles can be used as an adjunct for the rapid assessment of TMA and can help to differentiate it from other primary and secondary forms of TMA, allowing for earlier definitive therapy.

Where have all the platelets gone? HIT, DIC, or something else?

Thrombocytopenia in ill children is common; accurately diagnosing the underlying etiology is challenging and essential for appropriate management. Triggers for accelerated consumption of platelets are numerous; common downstream mechanisms of clearance include platelet trapping in microvascular thrombi, phagocytosis, and platelet activation. Thrombocytopenia with microangiopathic hemolytic anemia (MAHA) is frequently due to disseminated intravascular coagulation. Thrombotic microangiopathy (TMA) is a subgroup of MAHA. Specific TMA syndromes include thrombotic thrombocytopenic purpura, complement-mediated TMA (CM-TMA), and Shiga toxin-mediated hemolytic uremic syndrome. Isolated thrombocytopenia is characteristic of immune thrombocytopenia; however, concomitant cytopenias are frequent in critically ill patients, making the diagnosis difficult. Immune thrombocytopenia with large vessel thrombosis is a feature of heparin-induced thrombocytopenia and antiphospholipid antibody syndrome. In addition, thrombocytopenia is common with macrophage activation, which is characteristic of hemophagocytic lymphohistiocytosis. While thrombocytopenia in ill patients can be driven by hypoproliferative processes such as myelosuppression and/or bone marrow failure, this review will focus on consumptive thrombocytopenia due to immune and nonimmune causes.

Treatment Challenges of Acquired Thrombotic Thrombocytopenic Purpura in Pediatric Patients From a Low-Income Country

This study presents a comprehensive analysis of two cases of acquired thrombotic thrombocytopenic purpura (aTTP) observed in pediatric patients from a low-income country. In the instances described, both patients underwent a treatment regimen involving plasma exchange and immunosuppressive therapy conducted without the use of caplacizumab. Caplacizumab, an approved drug for adults known for its limited availability and high cost, has exhibited efficacy in reducing response time and recurrence frequency in aTTP cases. This approach resulted in significant clinical improvement and eventual remission of symptoms in one of the cases. These cases underscore the urgent necessity for a more inclusive approach in national health programs and international treatment guidelines. Specifically, there is a call to expand the existing comprehensive treatment algorithms to accommodate countries lacking access to caplacizumab. This adaptation aims to ensure the availability of suitable and effective treatment options for aTTP patients in regions facing limited pharmaceutical accessibility.

HUS and TTP: traversing the disease and the age spectrum

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP) are rare diseases sharing a common pathological feature, thrombotic microangiopathy (TMA). TMA is characterized by microvascular thrombosis with consequent thrombocytopenia, microangiopathic hemolytic anemia and/or multiorgan dysfunction. In the past, the distinction between HUS and TTP was predominantly based on clinical grounds. However, clinical presentation of the two syndromes often overlaps and, the differential diagnosis is broad. Identification of underlying pathogenic mechanisms has enabled the classification of these syndromes on a molecular basis: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS or complement-mediated TMA (aHUS/CM-TMA) associated with genetic or acquired defects leading to dysregulation of the alternative pathway (AP) of complement; and TTP that results from a severe deficiency of the von Willebrand Factor (VWF)-cleaving protease, ADAMTS13. The etiology of TMA differs between pediatric and adult patients. Childhood TMA is chiefly caused by STEC-HUS, followed by CM-TMA and pneumococcal HUS (Sp-HUS). Rare conditions such as congenital TTP (cTTP), vitamin B12 metabolism defects, and coagulation disorders (diacylglycerol epsilon mutation) present as TMA chiefly in children under 2 years of age. In contrast secondary causes and acquired ADAMT13 deficiency are more common in adults. In adults, compared to children, diagnostic delays are more frequent due to the wide range of differential diagnoses. In this review we focus on the three major forms of TMA, STEC-HUS, aHUS and TTP, outlining the clinical presentation, diagnosis and management of the affected patients, to help highlight the salient features and the differences between adult and pediatric patients which are relevant for management.

Current Intensive Care Management of Thrombotic Thrombocytopenic Purpura: A Case Report and Updated Literature Review

Thrombotic thrombocytopenic purpura (TTP), caused by severely reduced activity of the von Willebrand factor-cleaving protease ADAMTS13, is a medical emergency with life-threatening complications and a 90% mortality rate if left untreated. It presents a diagnostic challenge given the multiorgan involvement of the cardiovascular, gastrointestinal, and central nervous systems. Furthermore, the well-known full pentad of fever, hemolytic anemia, bleeding associated with thrombocytopenia, neurological signs, and renal disease is often absent in patients with TTP. We present a 51-year-old male adult with TTP. We utilized the PLASMIC scoring system, which predicts the likelihood of ADAMST13 activity in adults with features of thrombotic microangiopathy and thrombocytopenia with high sensitivity and specificity. We further review the literature supporting the expert statement on ICU management of patients with TTP that plasma exchange (PEX) should be initiated within 6 hours of diagnosis with adjunctive glucocorticoids, rituximab, and caplacizumab. If PEX is unavailable, plasma infusion can be started while the patient awaits transfer to a center with PEX capabilities.

Thrombotic thrombocytopenic purpura in a patient on long-term alpha-interferon therapy for essential thrombocythemia: a case report

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is rare and severe thrombotic microangiopathy characterized by thrombocytopenia, hemolytic anemia, and renal dysfunction. In contrast, essential thrombocythemia (ET) is a myeloproliferative disease associated with an abnormal increase in platelet numbers. Previous studies reported several cases of the development of ET in patients with TTP. However, the case of an ET patient complicated with TTP has not been previously reported. In this case study, we present a patient with TTP who was previously diagnosed with ET. Therefore, to the best of our knowledge, this is the first report of TTP in ET.

CASE PRESENTATION

A 31-year-old Chinese female who was previously diagnosed with ET presented with anemia and renal dysfunction. The patient had been on long-term treatment with hydroxyurea, aspirin, and alpha interferon (INF-α) for ten years. The diagnosis of TTP was confirmed by clinical features, schistocytes noted on the peripheral blood smear, and lower ADAMTS13 activity (8.5%), together with the renal biopsy results. INF-α was discontinued, and the patient was then treated with plasma exchange and corticosteroids. After one year of follow-up, the patient had a normal hemoglobin level and platelet numbers, and her ADAMTS13 activity had improved. However, the patient's renal function remains impaired.

CONCLUSIONS

We report a case of an ET patient complicated with TTP that was possibly due to INF-α, highlighting the potential complications associated with long-term ET therapy. The case also highlights the importance of considering TTP in patients with pre-existing ET who present with anemia and renal dysfunction, extending the spectrum of known studies.

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.

A Rare Case of Thrombotic Thrombocytopenic Purpura (TTP) With Concurrent Renal Cell Carcinoma: Diagnostic and Therapeutic Challenges

Thrombotic thrombocytopenic purpura (TTP) is a potentially life-threatening thrombotic microangiopathy (TMA) that needs prompt identification and treatment. Disseminated malignancy-related TMA can potentially be misdiagnosed as TTP, and patients may be inappropriately subjected to therapeutic plasma exchange (TPE) with serious implications. Likewise, the presence of a concurrent cancer diagnosis in a patient with microangiopathic hemolytic anemia and thrombocytopenia may lead to suspicion of disseminated malignancy as the cause, delaying the TPE with serious outcomes. Testing for ADAMTS13 activity is diagnostic of TTP, but the results may take time. This poses a diagnostic and therapeutic dilemma that includes weighing the benefits of TPE for treating TTP and cancer treatment. We describe a rare case of immune-mediated TTP in a patient concurrently diagnosed with metastatic renal cell cancer. To our knowledge, this is the first case of TTP reported in patients with metastatic renal cell carcinoma (RCC) in a non-treatment-naive patient.

Immune and Hereditary Thrombotic Thrombocytopenic Purpura: Can ADAMTS13 Deficiency Alone Explain the Different Clinical Phenotypes?

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy caused by a hereditary or immune-mediated deficiency of the enzyme ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). TTPs are caused by the following pathophysiological mechanisms: (1) the presence of inhibitory autoantibodies against ADAMTS13; and (2) hereditary mutations of the ADAMTS13 gene, which is present on chromosome 9. In both syndromes, TTP results from a severe deficiency of ADAMTS13, which is responsible for the impaired proteolytic processing of high-molecular-weight von Willebrand factor (HMW-VWF) multimers, which avidly interact with platelets and subendothelial collagen and promote tissue and multiorgan ischemia. Although the acute presentation of the occurring symptoms in acquired and hereditary TTPs is similar (microangiopathic hemolytic anemia, thrombocytopenia, and variable ischemic end-organ injury), their intensity, incidence, and precipitating factors are different, although, in both forms, a severe ADAMTS13 deficiency characterizes their physiopathology. This review is aimed at exploring the possible factors responsible for the different clinical and pathological features occurring in hereditary and immune-mediated TTPs.

The Specificities of Thrombotic Thrombocytopenic Purpura at Extreme Ages: A Narrative Review

Thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening thrombotic microangiopathy (TMA) related to a severe ADAMTS13 deficiency, the specific von Willebrand factor (VWF)-cleaving protease. This deficiency is often immune-mediated (iTTP) and related to the presence of anti-ADAMTS13 autoantibodies that enhance its clearance or inhibit its VWF processing activity. iTTP management may be challenging at extreme ages of life. International cohorts of people with TTP report delayed diagnoses and misdiagnoses in children and elderly people. Child-onset iTTP shares many features with adult-onset iTTP: a female predominance, an idiopathic presentation, and the presence of neurological disorders and therapeutic strategies. Long-term follow-ups and a transition from childhood to adulthood are crucial to preventing iTTP relapses, in order to identify the occurrence of other autoimmune disorders and psychosocial sequelae. In contrast, older iTTP patients have an atypical clinical presentation, with delirium, an atypical neurological presentation, and severe renal and cardiac damages. They also have a poorer response to treatment and prognosis. Long-term sequelae are highly prevalent in older patients. Prediction scores for iTTP diagnoses are not used for children and have a lower sensitivity and specificity in patients over 60 years old. ADAMTS13 remains the unique biological marker that is able to definitely confirm or rule out the diagnosis of iTTP and predict relapses during follow-ups.

Brazilian experience with caplacizumab in acquired thrombotic thrombocytopenic purpura: outcomes of the expanded access program

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare disease with an acute and severe clinical presentation. The anti-von Willebrand factor caplacizumab was licensed for adults with aTTP based on prospective controlled trials. However, until now, there was no Brazilian experience with this new treatment modality. This retrospective, multicenter, single-arm, expanded access program (EAP) with caplacizumab, plasma exchange (PEX), and immunosuppression was conducted between 02/24/21 and 04/14/21, and enrolled 5 Brazilian patients with aTTP. EAP allowed access to caplacizumab in Brazil and real-world data was collected, at a time when the medication was not commercially available in Brazil. The median age was 31 years old, most patients were women (80%), and neurological manifestation was observed in 80% of cases. The median of laboratory tests was hemoglobin (Hb) of 11 g/dL, platelets (16.1 × 10⁹/L), lactic dehydrogenase (LDH) of 1471 U/L, creatinine (0.7 mg/dL), ADAMTS13 activity lower than 0.71%, and PLASMIC score of 6. All patients received immunosuppression, PEX, and caplacizumab. Until clinical response was achieved, the median was 3 sessions of PEX and 3 days of treatment. The median time of caplacizumab use was 35 days, with platelet normalization in 2 days after starting the drug. The median total length of stay was 8 days. All patients achieved clinical response and clinical remission, with a good safety profile. There was rapid clinical response, few PEX sessions were necessary, and there were short hospital stay, absence of refractoriness, little exacerbation, no death, and resolution of signs and symptoms at diagnosis.

Diabetic Ketoacidosis Complicated by Thrombotic Thrombocytopenic Purpura: A Rare Association

Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially life-threatening blood disorder caused by a deficiency or dysfunction of ADAMTS13 and can occur secondary to various conditions, including autoimmune diseases, infections, medications, pregnancy, and malignancies. Diabetic ketoacidosis (DKA) inducing TTP is uncommon and not widely reported in the literature. Herein, we report a case of TTP induced by DKA in an adult patient. His clinical picture, serological, and biochemical results confirmed the diagnosis of TTP induced by DKA, and his clinical course did not improve despite normalization of glucose level, plasmapheresis, and aggressive management. Our case report emphasizes the importance of considering TTP as a potential complication of DKA.

From the Discovery of ADAMTS13 to Current Understanding of Its Role in Health and Disease

ADAMTS13 (a disintegrin-like metalloprotease domain with thrombospondin type 1 motif, member 13) is a protease of crucial importance in the regulation of the size of von Willebrand factor multimers. Very low ADAMTS13 activity levels result in thrombotic thrombocytopenic purpura, a rare and life-threatening disease. The mechanisms involved can either be acquired (immune-mediated thrombotic thrombocytopenic purpura [iTTP]) or congenital (cTTP, Upshaw-Schulman syndrome) caused by the autosomal recessive inheritance of disease-causing variants (DCVs) located along the ADAMTS13 gene, which is located in chromosome 9q34. Apart from its role in TTP, and as a regulator of microthrombosis, ADAMTS13 has begun to be identified as a prognostic and/or diagnostic marker of other diseases, such as those related to inflammatory processes, liver damage, metastasis of malignancies, sepsis, and different disorders related to angiogenesis. Since its first description almost 100 years ago, the improvement of laboratory tests and the description of novel DCVs along the ADAMTS13 gene have contributed to a better and faster diagnosis of patients under critical conditions. The ability of ADAMTS13 to dissolve platelet aggregates in vitro and its antithrombotic properties makes recombinant human ADAMTS13 treatment a potential therapeutic approach targeting not only patients with cTTP but also other medical conditions.

Adolescent acquired thrombotic thrombocytopenic purpura: An analysis of the Pediatric Health Information System database

The outcomes and characteristics of acquired thrombotic thrombocytopenic purpura (TTP) in adolescents is poorly understood due to an absence of studies focused on this population. To better understand the life-threatening disorder in this age, we performed an analysis of adolescent patients (ages 10-21) with TTP in the Pediatric Health Information Systems database from 2009 to 2020. The primary outcomes evaluated were in-hospital mortality and rate of TTP relapse. Secondary outcomes included rates of hemorrhagic and thrombotic complications during hospitalizations for TTP. Patients were included if they had a thrombotic microangiopathy diagnostic code, ADAMTS13 lab obtained, and received therapeutic plasmapheresis. Patients that received treatment for other non-TTP microangiopathies were excluded. A total of 99 patients with 123 hospitalizations for TTP treatment were identified. In-patient mortality occurred in 6 % (n = 6) and TTP relapse in 20 % (n = 20) of the cohort. Median time from initial admission to relapse was 33 days (IQR 15, 92). A hemorrhagic complication was identified in 29 % (n = 36) and thrombotic complication in 15 % (n = 19) of the cohort. The presence of underlying comorbidities was not associated with TTP relapse and only a diagnosis of cancer was associated with increased mortality. The rate of mortality and relapse in adolescent TTP is lower than that seen in adult registries. Long term prospective studies are needed to understand the long-term consequences of adolescent onset acquired TTP.

An update on the pathogenesis and diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Severe ADAMTS13 deficiency defines thrombotic thrombocytopenic purpura (TTP). ADAMTS13 is responsible for VWF cleavage. In the absence of this enzyme, widespread thrombi formation occurs, causing microangiopathic anemia and thrombocytopenia and leading to ischemic organ injury. Understanding ADAMTS13 function is crucial to diagnose and manage TTP, both in the immune and hereditary forms.

AREAS COVERED

The role of ADAMTS13 in coagulation homeostasis and the consequences of its deficiency are detailed. Other factors that modulate the consequences of ADAMTS13 deficiency are explained, such as complement system activation, genetic predisposition, or the presence of an inflammatory status. Clinical suspicion of TTP is crucial to start prompt treatment and avoid mortality and sequelae. Available techniques to diagnose this deficiency and detect autoantibodies or gene mutations are presented, as they have become faster and more available in recent years.

EXPERT OPINION

A better knowledge of TTP pathophysiology is leading to an improvement in diagnosis and follow-up, as well as a customized treatment in patients with TTP. This scenario is necessary to define the role of new targeted therapies already available or coming soon and the need to better diagnose and monitor at the molecular level the evolution of the disease.

Thrombotic Thrombocytopenic Purpura: From 1972 to 2022 and Beyond

This review tells the story of my personal experience with thrombotic thrombocytopenic purpura (TTP). It begins with my first encounter with TTP 50 years ago when 2 sisters presented 2 years apart, both pregnant and both died. At that time, I knew nothing about hereditary TTP (hTTP), the risks of pregnancy, or effective treatments. In 1991, a year after I moved to Oklahoma, therapeutic plasma exchange (TPE) was established as an effective treatment. With the availability of effective treatment, the number of patients presenting with suspected TTP soared. The diagnosis of TTP was imprecise. I worked with the Oklahoma Blood Institute (OBI) to understand the management of TTP. Because the OBI provided all TPE procedures for most of Oklahoma, we saw all consecutive patients within a defined geographic area who were identified at a uniform time early in the course of their TTP, without selection or referral bias. It was an inception cohort; this became the Oklahoma TTP Registry. In 2001, we began a very successful collaboration with the University of Bern, Switzerland, to measure ADAMTS13 activity in all of our patients. From our patients, we learned that acquired, autoimmune TTP (iTTP) is a chronic disease with risks for cognitive impairment and depression. Recognition in 2012 of three sisters with hTTP was reminiscent of the beginning of my story. hTTP has risks for multiple severe morbidities, beginning at birth and especially during pregnancy. Future management of both iTTP and hTTP will be more effective and more convenient.

Maternal and fetal outcomes of pregnancy occurring after a diagnosis of immune-mediated thrombotic thrombocytopenic purpura

Pregnancy is a well-established trigger for a first episode or relapse of immune thrombotic thrombocytopenic purpura (iTTP). Other outcomes of subsequent pregnancy after a diagnosis of iTTP are less well described. We conducted this retrospective cohort study to evaluate maternal and fetal outcomes of pregnancy in women with prior iTTP from the Johns Hopkins Thrombotic Microangiopathy Cohort. Of 168 women in the cohort, 102 were of reproductive age at diagnosis. Fourteen pregnancies (in 9 women) that occurred after the initial iTTP episode were included in the analysis. iTTP relapse occurred in 9 (64%) pregnancies. Out of the 9 instances of relapse, 5 relapses occurred in 2 women. Seven pregnancies (50%) ended in fetal death or miscarriage in the setting of iTTP relapse and three were electively terminated due to fear of relapse. Four pregnancies (50% of the 8 that progressed beyond 20 weeks) were complicated by preeclampsia or HELLP syndrome, which is over ten-fold higher than that of the general population. No maternal deaths occurred. Only 4 pregnancies resulted in live births, of which, 2 were pre-term. Pregnancy in women with prior iTTP is associated with a substantial risk of iTTP relapse and fetal loss. Preeclampsia and HELLP syndrome is also more common than that in the general population. ADAMTS13 monitoring and preemptive therapy may improve pregnancy outcomes, which needs to be evaluated prospectively.

A Case of Thrombotic Thrombocytopenic Purpura Possibly Induced by Graves' Disease

Thrombotic thrombocytopenic purpura (TTP) has historically been diagnosed with a pentad of features, i.e., thrombocytopenia, micro-angiopathic hemolytic anemia (MAHA), fever, neurological abnormalities, and kidney failure. Traditionally, TTP cases have been described in healthy adults. However, their association with autoimmune diseases is now well documented in the literature. There is limited availability of literature on the association between TTP and Graves' disease (GD). Here, we report a case of an adult female, a known case of Graves' disease, who has now been diagnosed with an acquired case of TTP. The presence of MAHA associated with thrombocytopenia was considered a clinical diagnosis of TTP and the patient immediately underwent plasma exchange (PEX), which led to the resolution of complaints. Hyperthyroidism cases should be adequately followed up as clinical severity could lead to the emergence of TTP.

Race, rituximab, and relapse in TTP

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is characterized by recurring episodes of thrombotic microangiopathy, causing ischemic organ impairment. Black patients are overrepresented in iTTP cohorts in the United States, but racial disparities in iTTP outcome and response to therapy have not been studied. Using the United States Thrombotic Microangiopathies Consortium iTTP Registry, we evaluated the impact of race on mortality and relapse-free survival (RFS) in confirmed iTTP in the United States from 1995 to 2020. We separately examined the impact of rituximab therapy and presentation with newly diagnosed (de novo) or relapsed iTTP on RFS by race. A total of 645 participants with 1308 iTTP episodes were available for analysis. Acute iTTP mortality did not differ by race. When all episodes of iTTP were included, Black race was associated with shorter RFS (hazard ratio [HR], 1.60; 95% CI, 1.16-2.21); the addition of rituximab to corticosteroids improved RFS in White (HR, 0.37; 95% CI, 0.18-0.73) but not Black patients (HR, 0.96; 95% CI, 0.71-1.31). In de novo iTTP, rituximab delayed relapse, but Black patients had shorter RFS than White patients, regardless of treatment. In relapsed iTTP, rituximab significantly improved RFS in White but not Black patients. Race affects overall relapse risk and response to rituximab in iTTP. Black patients may require closer monitoring, earlier retreatment, and alternative immunosuppression after rituximab treatment. How race, racism, and social determinants of health contribute to the disparity in relapse risk in iTTP deserves further study.

Incidence of thrombotic microangiopathies in Quebec: insight from a laboratory centralizing ADAMTS-13 testing

BACKGROUND

Thrombotic microangiopathies (TMA) are serious medical conditions requiring a prompt diagnosis to adapt treatment. The determination of ADAMTS-13 activity enables discriminating thrombotic thrombocytopenic purpura (TTP) from other forms of TMA. The purpose of this study was to provide an estimate of the incidence of TTP and TMA in the Canadian Quebec province using data collected from a laboratory centralizing ADAMTS-13 testing for the whole province.

RESULTS

From 2012 to 2019, 846 patients were evaluated for plasma ADAMTS-13 activity due to a suspicion of TMA. TTP was identified in 147 patients. Of these, 118 patients with a median age of 51.5 years and a male-female ratio of 1:1.4 had their first episode of TTP during the study period. The number of ADAMTS-13 tests performed and the number of patients with suspected TMA increased annually by 19% and 21% respectively. While the incidence of non-TTP TMA increased annually, that for TTP remained unchanged. This averaged 10.2 (95% CI 5.9-14.4) per million persons per year for suspected non-TTP TMA and 1.8 (95% CI 1.3-2.4) for confirmed TTP. The incidence rate of TMA other than TTP was higher in the age group 70-79 years (21.8; 95% CI 5.4-38.1) for females and in the age group 80-89 years (24.4; 95% CI 7.2-41.7) for males compared to other age groups. The incidence rate of TTP was higher in the age group 40-49 years (4.0; 95% CI 2.0-5.9) for women and in the age group 60-69 years (3.4; 95% CI 1.1-5.6) for men compared to other age groups.

CONCLUSION

The analysis of centralized data measuring ADAMTS-13 activity allowed us to adequately establish the incidence rate and demographic characteristics of TMA, particularly TTP, in Quebec. TTP incidence remained stable while suspected non-TTP TMA steadily increased from 2012 to 2019.

COVID-19-Associated Thrombotic Thrombocytopenic Purpura: A Case Report and Systematic Review

Introduction: The proliferation of literature regarding the COVID-19 pandemic has served to highlight a wide spectrum of disease manifestations and complications, such as thrombotic microangiopathies. Our review with a brief case presentation highlights the increasing recognition of TTP in COVID-19 and describes its salient characteristics. Methods: We screened the available literature in PubMed, EMBASE, and Cochrane databases from inception until April 2022 of articles mentioning COVID-19-associated TTP in English language. Results: From 404 records, we included 8 articles mentioning data of 11 patients in our review. TTP was predominantly reported in females (72%) with a mean age of 48.2 years (SD 15.1). Dyspnea was the most common symptom in one third of patients (36.6%). Neurological symptoms were reported in 27.3% of cases. The time to diagnosis of TTP was 10 days (SD 5.8) from onset of COVID-19. All 11 cases underwent plasma exchange (PLEX), with a mean of 12 sessions per patient, whereas 6 cases received Rituximab (54.5%), and 3 received Caplacizumab (27.3%). One patient died from the illness. Conclusion: This review of available literature highlights the atypical and refractory nature of COVID-19-associated TTP. It required longer sessions of PLEX, with half of the patients receiving at least one immunosuppressant.

Recommendations for the diagnosis and treatment of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) characterized by the development of microangiopathic haemolytic anaemia, thrombocytopenia, and ischaemic organ dysfunction associated with ADAMTS13 levels lower than 10% in most cases. Recently there have been numerous advances in the field of PTT, new, rapid and accessible techniques capable of quantifying ADAMTS13 activity and inhibitors. The massive sequencing systems facilitate the identification of polymorphisms in the ADAMTS13 gene. In addition, new drugs such as caplacizumab have appeared and relapse prevention strategies are being proposed with the use of rituximab. The existence of TTP patient registries allow a deeper understanding of this disease but the great variability in the diagnosis and treatment makes it necessary to elaborate guidelines that homogenize terminology and clinical practice. The recommendations set out in this document were prepared following the AGREE methodology. The research questions were formulated according to the PICO format. A search of the literature published during the last 10 years was carried out. The recommendations were established by consensus among the entire group, specifying the existing strengths and limitations according to the level of evidence obtained. In conclusion, this document contains recommendations on the management, diagnosis, and treatment of TTP with the ultimate objective of developing guidelines based on the evidence published to date that allow healthcare professionals to optimize TTP treatment.

Acquired Thrombotic Thrombocytopenic Purpura Following Inactivated COVID-19 Vaccines: Two Case Reports and a Short Literature Review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in December 2019, causing millions of deaths all over the world, and the lack of specific treatment for severe forms of coronavirus disease 2019 (COVID-19) have led to the development of vaccines in record time, increasing the risk of vaccine safety issues. Recently, several cases of thrombotic thrombocytopenic purpura (TTP) have been reported following COVID-19 vaccination. TTP is a rare disease characterized by thrombocytopenia, microangiopathic hemolytic anemia and ischemic end-organ lesions. It can be either congenital or acquired. Various events such as viral infections, medication, pregnancy, malignancies, and vaccinations may cause TTP. Here, we report two cases of acquired TTP following Sinopharm COVID-19 vaccine (BBIBP-CorV) and Sinovac COVID-19 vaccine (CoronaVac). Diagnosis was based on clinical presentation and confirmed with a severe reduction in the activity of von Willebrand factor-cleaving protease ADAMTS-13 and the presence of inhibitory autoantibodies. The two patients were successfully treated with corticosteroids, plasma exchange therapy and rituximab in the acute phase. In the literature, the reported cases of TTP induced by COVID-19 vaccination occurred after Adenoviral Vector DNA- and SARS-CoV-2 mRNA-Based COVID-19 vaccines. To the best of our knowledge, this is the first report of acquired TTP after inactivated virus COVID-19 vaccination.

Lombardy diagnostic and therapeutic network of thrombotic microangiopathy

Background

Thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening thrombotic microangiopathy (TMA) requiring urgent treatment. Standardization of its diagnosis and optimal management is challenging. This study aimed to evaluate the role of centralized, rapid testing of ADAMTS13 in patients experiencing acute TMAs requiring plasma-exchange (PEX) and to estimate the incidence of TTP in a large Italian Region.

Methods

We perfomed a cohort study in the frame of the project “Set-up of a Lombardy network for the study and treatment of patients undergoing apheresis”, including 11 transfusion centers in the Region. Consecutive patients referred from 2014 to 2016 with acute TMAs requiring PEX were enrolled. Centralized ADAMTS13 activity testing was performed at the Milan Hemophilia and Thrombosis Center within 24 h.

Results

Forty-three TMA patients (44 events) were enrolled, of whom 35 (81%) had severe ADAMTS13 deficiency. Patients with severe ADAMTS13 deficiency were younger, mainly women, with a higher prevalence of autoimmune disorders and a lower prevalence of cancer. Clinical and laboratory characteristics of patients with and without severe ADAMTS13 deficiency largely overlapped, with a lower platelet count being the only baseline marker that significantly differed between the two patient groups (ADAMTS13 activity < 10% vs ≥ 10%: median difference of -27 × 10⁹/l, 95% CI − 37 to − 3). PEX treatment was initiated in all patients, but soon discontinued in cases without severe ADAMTS13 deficiency. In this group, the mortality rate was higher and no episode exacerbations or relapses within 6 months occured. The estimated average annual incidence of acute acquired TTP events was 1.17 [0.78–1.55] per million people.

Conclusions

Severe ADAMTS13 deficiency distinguished two groups of patients with largely overlapping clinical features but different treatment and disease course. This study provides a feasible model implemented in a large Italian region for the practical clinical approach to TMAs and underlines the importance of urgent ADAMTS13 activity testing for an accurate differential diagnosis and therapeutic approach.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02400-y.

Effect of Blood Groups on Clinical Presentations and Treatment Outcomes in Immune Thrombotic Thrombocytopenic Purpura Patients with Severe ADAMTS13 Deficiency: A Multi-Center Experience

Introduction

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy caused by accumulation of ultra-large von Willebrand factor (vWF) due to the significantly reduced activity ADAMTS13. Limited studies have been published examining the blood group as an epidemiological factor that can contribute to development of TTP. It has been suggested that due to low vWF levels, the distribution of the "O" blood group among TTP patients may be lower than anticipated compared to the blood group distribution rates in the normal population. The aim of this study was to explore the relationship between blood groups and the clinical outcome of immune TTP (iTTP).

Methods

Thirty patients with iTTP with severe ADAMTS13 deficiency were enrolled. Data collection commenced in January 2011 and was completed by June 2020. It was analyzed whether there was a difference between the blood groups in terms of frequency of iTTP, response to treatment, frequency of relapse, and clinical and laboratory results.

Results and Conclusions

The distribution of group "A" among patients with iTTP was higher than expected. Although not statistically significant, patients with blood group "O" required more TPE for the treatment and relapse rate was statistically higher than other blood groups. Mortality rate in all patients was 6.7%. Although blood group "A" is a risk factor for iTTP, the frequency of relapse is higher in the blood group "O."

Immune-Mediated Thrombotic Thrombocytopenic Purpura Following mRNA-Based COVID-19 Vaccine BNT162b2: Case Report and Mini-Review of the Literature

Introduction

An increasing number of case reports have associated vaccinations against coronavirus disease 2019 (COVID-19) with immune-mediated thrombotic thrombocytopenic purpura (iTTP), a very rare but potentially life-threatening thrombotic microangiopathy, which leads to ischemic organ dysfunction. Thrombus formation in iTTP is related to a severe deficiency of the specific von Willebrand-factor-cleaving protease ADAMTS13 due to ADAMTS13 autoantibodies.

Methods

We present a case of iTTP following exposure to the mRNA-based COVID-19 vaccine BNT162b2 (Comirnaty^®, Pfizer-BioNTech). In addition, we review previously reported cases in the literature and assess current evidence.

Results

Apart from our case, twenty cases of iTTP occurring after COVID-19 vaccination had been published until the end of November 2021. There were 11 male and 10 female cases; their median age at diagnosis was 50 years (range 14–84 years). Five patients (24%) had a preexisting history of iTTP. Recombinant adenoviral vector-based vaccines were involved in 19%, mRNA-based vaccines in 81%. The median onset of symptoms after vaccination was 12 days (range 5–37), with 20 cases presenting within 30 days. Treatment included therapeutic plasma exchange in all patients. Additional rituximab, caplacizumab, or both these treatments were given in 43% (9/21), 14% (3/21), and 24% (5/21) of cases, respectively. One patient died, despite a prolonged clinical course in one patient, all surviving patients were in clinical remission at the end of the observational period.

Conclusion

Clinical features of iTTP following COVID-19 vaccination were in line with those of pre-pandemic iTTP. When timely initiated, an excellent response to standard treatment was seen in all cases. ADAMTS13 activity should be determined pre-vaccination in patients with a history of a previous iTTP episode. None of the reported cases met the WHO criteria for assessing an adverse event following immunization (AEFI) as a consistent causal association to immunization. Further surveillance of safety data and additional case-based assessment are needed.

Recent advances in the management of immune-mediated thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially life-threatening thrombotic microangiopathy caused by autoantibody-mediated severe ADAMTS13 deficiency. TTP should be suspected in patients with microangiopathic hemolytic anemia and thrombocytopenia without a definite cause. Early detection of iTTP and prompt treatment with plasma exchange and corticosteroids are essential. Rituximab administration should be considered for refractory or relapsed iTTP, and can be used as a first-line adjuvant or preemptive therapy. Treatment with caplacizumab, a novel anti-von Willebrand factor nanobody, resulted in a faster time to platelet count response, significant reduction in iTTP-related deaths, and reduced incidence of refractory iTTP. TTP survivors showed a higher rate of chronic morbidities, including cardiovascular disease and neurocognitive impairment, which can lead to a poor quality of life and higher mortality rate. Meticulous long-term follow-up of TTP survivors is crucial.

Thrombotic microangiopathies: An illustrated review

The thrombotic microangiopathies (TMAs) are a heterogenous group of disorders with distinct pathophysiologies that cause occlusive microvascular or macrovascular thrombosis, and are characterized by microangiopathic hemolytic anemia, thrombocytopenia, and/or end-organ ischemia. TMAs are associated with significant morbidity and mortality, and data on the management of certain TMAs are often lacking. The nomenclature, classification, and management of various TMAs is constantly evolving as we learn more about these rare syndromes. Thorough clinical and laboratory evaluation is essential to distinguish various TMAs and arrive at an accurate diagnosis, which is key for appropriate management. In this illustrated review, we focus on thrombotic thrombocytopenic purpura (TTP), Shiga toxin-associated hemolytic uremic syndrome, complement-mediated hemolytic uremic syndrome, hematopoietic cell transplant-associated TMA, and drug-induced TMA, and describe their incidence, pathophysiology, diagnosis, and management. We also highlight emerging complement-directed therapies under investigation for the management of complement-mediated TMAs.

Unusual Presentation of Thrombotic Thrombocytopenic Purpura in a Newly Diagnosed Pediatric Patient With Systemic Lupus Erythematosus in the Setting of MIS-C

The understanding of coronavirus disease 2019 (COVID-19) immune dysregulation is evolving. Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with alternations in both innate and adaptive immunity, probably caused by a complex interplay of genetics and environmental exposure with various triggers. A rare hematological complication of SLE as well as recently reported in an adult with COVID-19 is thrombotic thrombocytopenic purpura. We report a pediatric case with features suggestive of the multisystem inflammatory syndrome in children with coronary artery ectasia, thrombotic thrombocytopenic purpura, and new-onset SLE.

Role of therapeutic apheresis in the treatment of pediatric kidney diseases

Therapeutic apheresis utilizes apheresis procedures in the treatment of a variety of conditions including kidney disease. Therapeutic plasma exchange (TPE) is the most common modality employed with the rationale of rapid reduction of a pathogenic substance distributed primarily in the intravascular compartment; however other techniques which adsorb such pathogenic substances or alter the immune profile have been utilized in diseases affecting native and transplanted kidneys. This article discusses the modalities and technical details of therapeutic apheresis and summarizes its role in individual diseases affecting the kidney. Complications related to pediatric apheresis procedures and specifically related to apheresis in kidney disease are also discussed. Though therapeutic apheresis modalities are employed frequently in children with kidney disease, most experiences are extrapolated from adult studies. International and national registries need to be established to elucidate the role of apheresis modalities in children with kidney disease.

Systemic Lupus Erythematosus Presenting With Thrombotic Thrombocytopenic Purpura at Onset: A Case Report

BACKGROUND

Thrombotic microangiopathy (TMA) is a syndrome associated with hemolytic anemia, thrombocytopenia, and various organ disorders. Thrombotic thrombocytopenic purpura (TTP) is a disease that develops when a disintegrin-like and metalloproteinase with thrombospondin type l motif 13 (ADAMTS13) activity decreases to < 10% of that in normal plasma, causing platelet thrombosis in microvessels throughout the body. Currently, ADAMTS13-deficient TMA is diagnosed as TTP. Systemic lupus erythematosus (SLE)-related TMA includes both acquired TTP, in which ADAMTS13 activity is significantly reduced, and secondary TMA, in which ADAMTS13 activity is not reduced. Both diseases have different prognoses.

CASE PRESENTATION

An 11-year-old girl was admitted to our hospital on suspicion of TMA with thrombocytopenia and hemolytic anemia. Because the patient had hypocomplementemia, SLE-related TMA or complement-related TMA was considered. Therefore, we initiated plasma exchange (PE) for the patient. Subsequently, she fulfilled the pediatric SLE diagnostic criteria, and ADAMTS13 activity was shown to be decreased and the anti-ADAMTS13 antibody titer increased. She was thus diagnosed with acquired TTP caused by SLE. Treatment response was good as a platelet count and ADAMTS13 activity improved with three times of PE, followed by methylprednisolone pulse therapy and administration of mycophenolate mofetil. Renal pathology showed thrombus formation in glomerular arterioles and lupus nephritis categorized as Class III (A) of the International Society of Nephrology and the Renal Pathology Society classification. Because the patient was thought to be in the high-risk group of SLE, three courses of intravenous cyclophosphamide pulse therapy were administered as an additional induction therapy. No recurrence of TTP was observed.

CONCLUSION

In SLE-related TMA, measurement of ADAMTS13 activity and the anti-ADAMTS13 antibody titer are necessary for diagnosis, and for predicting prognosis and recurrence of the disease; however, in the acute phase of immune-mediated TMA, it is important to initiate proper treatments even before knowing the results to improve prognosis.