Consensus on the standardization of terminology in thrombotic thrombocytopenic purpura and related thrombotic microangiopathies

Early administration of caplacizumab combined with plasma exchange for thrombotic microangiopathy due to malignant hypertension: a case report

Both thrombotic thrombocytopenic purpura (TTP) and malignant hypertension (MHT) present with thrombotic microangiopathy (TMA). Combination therapy with caplacizumab, anti-von Willebrand factor (VWF) A1 domain antibody, and plasma exchange (PE) has recently been highlighted as a novel therapeutic option for TTP. We treated a 51-year-old woman who showed severe hypertension, retinopathy, and acute kidney injury. Level of consciousness was clear on admission, but low-grade fever was observed. Laboratory tests showed normocytic anemia, thrombocytopenia, renal dysfunction, and a slight decrease in haptoglobin. Neither disseminated intravascular coagulation nor leukemia was diagnosed. The patient emergently received intravenous antihypertensive therapy, continuous hemodiafiltration, and sufficient blood transfusion. However, thrombocytopenia and oliguria remained despite control of blood pressure. On hospital day 8, administration of caplacizumab combined with PE was initiated before receiving results for a disintegrin-like and metalloprotease with thrombospondin type 1 motifs 13 (ADAMTS13) activity and inhibitor levels. We then administered caplacizumab for 5 days and performed 2 sessions of PE until confirming ADAMTS13 activity of 42% and absence of its inhibitor, contributing to increased serum hemoglobin and platelet levels with cessation of dialysis. Renal biopsy findings on hospital day 20 showed arteriolar nephrosclerosis and intimal hyperplasia in small arteries. To the best of our knowledge, this represents the first description of MHT-induced TMA treated with caplacizumab. MHT-induced TMA exhibiting symptoms of TTP tends to show poor renal prognosis, so early administration of caplacizumab with PE before receiving results for ADAMTS13 might prove beneficial for cases in which MHT complicated with TTP is suspected.

Thrombotic thrombocytopenic purpura following plastic surgery: A case report

Thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening condition characterized by thrombocytopenia, microangiopathic hemolytic anemia, and potential multi-organ involvement. Typically, TTP is associated with underlying conditions such as autoimmune diseases, infections, cancer, or hereditary factors. To date, very few cases of post-operative TTP have been reported. We report the first known case of TTP following plastic surgery. A 19-year-old female initially recovered uneventfully after breast reduction surgery but presented on postoperative day 7 with a persistent hematoma, worsening anemia, and thrombocytopenia. The diagnosis of TTP was confirmed following hematoma evacuation, with laboratory results showing severe hemolysis and a marked reduction in ADAMTS13 activity. The patient was promptly treated with plasma exchange, corticosteroids, and rituximab, which led to significant clinical improvement and resolution of hematological abnormalities. This case underscores the rarity of TTP following plastic surgery, where it is more often linked to other medical conditions. Early recognition and management of TTP, particularly with plasma exchange, are crucial to preventing complications and improving patient outcomes. Although endothelial damage during surgery may contribute to the onset of TTP, the causal link in this case remains uncertain. Awareness of TTP as a potential postoperative complication is essential, especially when dealing with persistent anemia, bleeding, or thrombocytopenia.

Long-Term Outcomes of Anticomplement Factor H Antibody Positive Versus Negative Atypical Hemolytic Uremic Syndrome

Background

Atypical hemolytic uremic syndrome (aHUS) is a severe thrombotic microangiopathy predominantly affecting the kidneys, often associated with complement dysregulation. This study is aimed to analyze the clinical characteristics, treatment outcomes, and long-term implications of aHUS in a resource-limited setting.

Materials and Methods

A retrospective observational study conducted at an institute between January 2016 and December 2022 included all patients with aHUS, excluding secondary causes and renal transplant recipients. Demographic profiles, clinical features, laboratory parameters, treatment modalities (immunosuppression and plasma exchange), and outcomes were collected. Anticomplement Factor H (anti-CFH) antibody, complement levels, and genetic mutation analysis were performed to ascertain etiological factors. The patient and renal outcomes of anti-CFH positive and negative patients on long-term follow-up were compared.

Results

Fifty-seven patients (mean age: 12.5 ± 4.9 years; 63% males) were analyzed. Among them, 33 (57.9%) tested positive for anti-CFH antibodies and eight presented postpartum. Initial remission was achieved in 42 (73.6%) patients, with 13 (22.8%) partial and 29 (50.9%) complete remission. The median follow-up duration was 24 months [interquartile range (IQR) 8.5-84]; 12 (21%) patients died, with two deaths during the index admission, six among nonresponders, and 4 among responders. Dialysis-free renal survival was superior in anti-CFH seropositive patients (81.2%) compared to seronegative counterparts (55.9%), while patient survival was statistically similar between the two groups. Elevated anti-CFH titers (>4000 AU/ml), age ≥16 years, female gender, and seizures predicted nonresponsiveness.

Conclusion

Anti-CFH antibody associated aHUS had better kidney outcomes than the seronegative counterparts. In resource limited settings, a combination of plasma exchange and immunosuppression showed promising results in the short and long term.

Thrombotic Thrombocytopenic Purpura in Pediatric Patients

Thrombotic thrombocytopenia purpura is a serious disease that can involve complex symptomatology, prolonged hospitalization, and a high risk of mortality if treatment is delayed. This disease is rare, but it is even rarer among pediatric patients. Even though it was first described 100 years ago, the earliest documented case was a pediatric patient. The last three decades have seen the discovery of the pathological mechanisms responsible for its clinical presentation. Symptoms/signs characteristic of microangiopathic hemolytic anemia with significant thrombocytopenia characterize the vast majority of patients. Its pathology centers on the accumulation of ultra-large von Willebrand factor multimers due to an enzyme deficiency that prevents their breakdown. Currently, in pediatric patients, two forms of the disease are known: congenital due to a mutation in the enzyme's gene and immune-mediated due to enzyme depletion or neutralization secondary to autoantibody formation. With the advent of therapeutic plasma exchanges, immunosuppression, and, more recently, a TTP-specific nanobody, there is reason for optimism that the disease does not necessarily equate to a bad outcome. Thus, the aim of this review is to contrast the congenital and immune-mediated forms of the disease in pediatric patients while presenting them in the context of their pathologic mechanisms, diagnosis, and treatment.

Multidisciplinary consensus on the diagnosis and management of patients with atypical Hemolytic Uremic Syndrome (complement-mediated TMA): Recommendations from Italian scientific societies, patient associations and regulators

Atypical Hemolytic Uremic Syndrome (aHUS) is a severe, systemic, rare disease (RD) that can occur in people of all ages, and is associated with high rates of morbidity and mortality. Because the management of patients with aHUS can be difficult, more effective strategies should be implemented. Faculty members from several Italian Scientific Societies, Patient Associations and Regional Institutional Experts on RDs met to discuss aHUS management within a multidisciplinary team (MDT), using a Delphi process to develop consensus recommendations. Consensus (≥70 % agreement by faculty members) was reached on 51 statements with the aim of improving patient management and outcomes. These statements provide a unified framework for the differential diagnosis of aHUS, prompt recognition of the pathology, referral to RD reference centers, selecting between treatment relapse prevention measures options, patient management by a MDT and improving the overall awareness of aHUS. Despite the broad scope of the consensus statements, several unmet needs in the management of patients with aHUS were identified, including diagnostic suspicion, rapid genetic investigations, regular review of the centers of expertise (considering the number of treated patients), permanent clinical referral in treatment centers and widespread expertise among adult and pediatric specialists. We hope that this standardized framework will form the basis of the "digital ecosystem" concept and development of possible information technology solutions to assist the MDT involved in the management of patients with aHUS.

Caplacizumab use in immune-mediated thrombotic thrombocytopenic purpura: an international multicentre retrospective Cohort study (The Capla 1000+ project)

Background

The anti-Von Willebrand Factor (VWF) nanobody caplacizumab is licensed for adults with immune-mediated thrombotic thrombocytopenic purpura (iTTP) in association with therapeutic plasma exchange (TPE) and immunosuppression. However, whether caplacizumab reduces mortality, and its optimal timing of initiation, is not completely settled.

Methods

This international, multicenter retrospective cohort study recruited patients from 2018 until 2023 and data collection took place from January 1st to June 30th 2023 in the participating centers. One thousand and fifteen patients were treated with daily TPE, immunosuppression with corticosteroids ± rituximab, and caplacizumab (caplacizumab group), which was compared to historic controls treated with TPE and corticosteroids ± rituximab (control group, N = 510). Caplacizumab initiation was classified as early (within 3 days; 76% of cases) or delayed (≥4 days from first TPE).

Findings

Three-month survival rate in the caplacizumab group was 98.5%, compared with 94% in controls (P < 0.0001). Three-month mortality rate was 4.2-fold higher in controls than in caplacizumab-treated patients (95% CI: 2.22-7.7, P < 0.0001), regardless of rituximab use. In both groups, death was observed primarily in elderly patients, and age was the factor most associated with 3-month mortality. Patients receiving caplacizumab showed reduced refractoriness, exacerbations, and required fewer TPE sessions to achieve clinical response versus controls (P < 0.0001 all). Time to clinical response in the caplacizumab group was shorter than in controls, and even shorter in patients with early caplacizumab initiation (P < 0.0001 both). Caplacizumab-related adverse events were observed in 21% of patients, with major bleeding in 2.4%, which was more common in elderly patients.

Interpretation

The early association of Caplacizumab to TPE and immunosuppression significantly reduces unfavorable outcomes during iTTP, including death, and alleviates the burden of care at the potential expense of bleeding events. Advanced age, however, remains an adverse factor for survival. The limitations of our study include its retrospective and multicentric design and the use of a historical control cohort.

Funding

None.

Bortezomib for rituximab-refractory immune-mediated thrombotic thrombocytopenic purpura in the caplacizumab era: an Italian multicenter study

BACKGROUND

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) patients are not responsive to standard rituximab in approximately 10% to 15% of cases, and oral immunosuppressants showed controversial results with significant toxicity. Targeting plasma cells with bortezomib appears promising, but the available evidence is scarce and stems only from isolated reports in the precaplacizumab era.

OBJECTIVES

To evaluate the safety and efficacy of bortezomib in rituximab-refractory iTTP patients.

METHODS

We conducted a retrospective observational multicenter study among 13 Italian iTTP treating centers, collecting data from May 2017 to May 2023 (caplacizumab was licensed in Italy in January 2020).

RESULTS

Bortezomib was effective in 10/17 patients (59%). Eleven were treated in the acute phase (9/11 responders, 82%, allowing discontinuation of caplacizumab in 5/6 treated patients), and 7 during clinical remission (2/7 responders, 28%). Responses occurred at a median time of 30 days, but 3 patients responded after 4 months. The median duration of response was 22 months (IQR, 10-38), still ongoing in 6 patients at the time of data cutoff. Responders had fewer previous acute iTTP episodes than nonresponders (median [IQR], 1 [1,2] vs 5.5 [2-7]; P = .03). Eight subjects (47%) reported toxicities, mostly in those treated with ≥2 cycles.

CONCLUSION

Durable responses to bortezomib were registered in about 60% of multirefractory iTTP patients with mild to moderate toxicities. The occurrence of late responses (ie, after 30 days) suggests a "watchful waiting" approach after bortezomib treatment.

Targeting complement in kidney transplantation: Therapeutic approaches based on preclinical and experimental evidence

The complement system is implicated in various facets of kidney transplantation, including ischemia-reperfusion injury (IRI), delayed graft function, allograft rejection, and chronic allograft injury. IRI, prevalent in cadaveric renal transplantation, leads to acute tubular necrosis and engages innate immunity, including neutrophils and the complement system, fostering a cycle of inflammation and necrosis. Experimental and preclinical evidence suggest that targeting the complement system could offer therapeutic benefits in IRI during kidney transplantation. This article explores potential therapeutic approaches targeting complement pathways in kidney transplantation, drawing from experimental and preclinical research findings.

Cost-effectiveness of caplacizumab in immune thrombotic thrombocytopenic purpura in the United States

BACKGROUND

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening thrombotic microangiopathy. Caplacizumab is the only treatment approved by the European Medicines Agency and the US Food and Drug Administration for iTTP, to be given in combination with plasma exchange therapy (PEX) and immunosuppression (IS). The National Institute for Health and Care Excellence's independent appraisal committee assessed the cost-effectiveness of caplacizumab and concluded that the addition of caplacizumab to PEX+IS is cost-effective under a patient access scheme in the United Kingdom.

OBJECTIVE

To assess the cost-effectiveness of caplacizumab in iTTP from the US payer perspective.

METHODS

The National Institute for Health and Care Excellence's model was adapted to the US setting using US costs and discount rates. In contrast to previous cost-effectiveness analyses that accounted only for acute outcomes, our model consisted of a 3-month decision tree for an acute iTTP episode, followed by a Markov model to project long-term costs and outcomes (time horizon: up to 55 years; 3-monthly cycles).

RESULTS

Patients taking caplacizumab with PEX+IS experienced an incremental gain of 2.96 life years (LYs) and 1.75 quality-adjusted LYs relative to PEX+IS alone, at an increased lifetime cost of $256,000. The incremental cost-effectiveness ratio was $86,400 per LY and $146,300 per quality-adjusted LY gained.

CONCLUSIONS

Considering willingness-to-pay thresholds of $150,000 to $200,000, the addition of caplacizumab to PEX+IS may be cost-effective compared with PEX+IS alone for the treatment of iTTP in a US setting.

Clinical and economic burden of suspected thrombotic thrombocytopenic purpura in US hospitals

PURPOSE

Severe ADAMTS13 deficiency (activity <10%) is the diagnostic threshold for thrombotic thrombocytopenic purpura (TTP) and is associated with various clinical symptoms, abnormal laboratory results, and long-term complications.

METHODS

This retrospective, noninterventional cohort study used the Premier Healthcare Database to identify patients with ADAMTS13 activity of <10% in US hospitals from January 1, 2016, through March 31, 2020. The objective was to describe patient characteristics, laboratory results, comorbidities (as measured by the Elixhauser comorbidity index), symptoms, length of stay, treatment patterns, mortality, inpatient costs, and readmission rates (summarized descriptively). Inpatient costs were calculated as total cost to the hospital.

RESULTS

There were 211 patients with severe ADAMTS13 deficiency; 89% of patients had a TTP-related diagnosis, of whom 62% had a primary diagnosis of thrombotic microangiopathy. Over 80% of patients with available data had a decreased platelet count and elevated lactate dehydrogenase; schistocytes were detected in 99%. The most prevalent symptoms/complications were neurological, bleeding, and pain. Most patients (86%) had 2 or more Elixhauser comorbidities. Over 80% of patients received 1 or more TTP-related treatments, mostly plasma exchange. The mean length of stay was 11.5 days; 5% of patients died during their stay. Readmission rates at 30, 60, and 90 days were 20%, 26%, and 28%, respectively. The median (interquartile range) total inpatient cost to the hospital throughout the index admission was $33,221 ($19,431-$64,901).

CONCLUSION

Patients with severe ADAMTS13 deficiency have substantial clinical burden, have high mortality and readmission rates, and generate high costs for hospitals. There is a high need for a therapy that replaces ADAMTS13, thus addressing the root cause of the symptoms and complications caused by this deficiency.

Therapeutic Plasma Exchange Management for a Pediatric Patient Presenting With Immune Thrombotic Thrombocytopenic Purpura in a Setting of Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is a disorder characterized by hypogammaglobulinemia resulting in recurrent infections. While autoimmune disorders are common in patients with CVID, no association has been reported between CVID and immune thrombotic thrombocytopenic purpura (iTTP), a disorder most often caused by autoantibodies that compromise the activity of the enzyme ADAMTS13. Reduced ADAMTS13 activity results in the accumulation of large von Willebrand factor multimers that can consume platelets and cause microvascular thrombosis and organ injury, ultimately resulting in mortality in most cases of untreated iTTP. Here, we report a 12-year-old male with CVID who developed iTTP, underwent therapeutic plasma exchange (TPE), and subsequently recovered. We conducted a systematic review for other cases of CVID co-occurring with iTTP and present additional cases of this rare presentation. We highlight the importance of prompt recognition of iTTP in a patient with CVID and timely initiation of TPE.

Carfilzomib-associated thrombotic microangiopathy: clinical features and outcomes

BACKGROUND

Carfilzomib, a new proteasome inhibitor indicated for patients with relapsed/refractory myeloma, has been associated with cases of thrombotic microangiopathy (CFZ-TMA). The role of variants in the complement alternative pathway and therapeutic potential of complement blockade with eculizumab remain to be determined.

METHODS

We report 37 cases of CFZ-TMA recorded in the French reference center for TMA with their clinical characteristics, genetic analysis and outcome according to treatments.

RESULTS

A trigger was identified in more than half of cases, including eight influenza and five severe acute respiratory syndrome coronavirus-2 cases. All patients presented with acute kidney injury (AKI) [KDIGO stage 3 in 31 (84%) patients] while neurological (n = 13, 36%) and cardiac (n = 7, 19%) damage were less frequent. ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type I repeats-13) and complement activity were normal (n = 28 and 18 patients tested) and no pathogenic variant in the alternative complement pathway was found in 7 patients tested. TMA resolved in most (n = 34, 94%) patients but 12 (44%) still displayed stage 3 AKI at discharge. Nineteen (51%) patients were treated with therapeutic plasma exchange, 14 (38%) patients received corticosteroids and 18 (50%) were treated with eculizumab. However, none of these treatments demonstrated a significant impact on outcomes.

CONCLUSION

This study is the largest case series of CFZ-TMA since its approval in 2012. Patients present with severe AKI and experience frequent sequelae. Complement variants and blockade therapy do not seem to play a role in the pathophysiology and prognosis of the disease.

Initial US tertiary health care system experience using caplacizumab in patients with immune thrombotic thrombocytopenic purpura

Several international registries have reported on the efficacy of caplacizumab for the treatment of immune thrombotic thrombocytopenic purpura (iTTP). Similar real-world data from the United States (US) are limited. In this single center retrospective study, we sought to describe caplacizumab prescribing patterns and review clinical outcomes for US patients with iTTP. Subjects were eligible for inclusion if they were diagnosed with acute iTTP and received care at University of Pittsburgh Medical Center-affiliated hospitals from 2012 to 2022. Subjects were divided into an historical cohort who received standard of care therapy alone, and early and late administration cohorts (EA and LA) who received caplacizumab within and greater than 72 h of admission, respectively, plus standard of care. Clinical data were collected from the electronic record. Thirty-two subjects were included: 16 historical, 12 EA, and 4 LA subjects. Refractoriness occurred more frequently in the LA and historical cohorts as compared to the EA cohort (4 (100%) vs. 6 (38%) vs. 3 (25%), p = 0.02). The LA cohort also experienced longer lengths of hospital stay, required more TPE procedures, and were exposed to the greatest amount of donor plasma (p < 0.05 for all) as compared to the other cohorts. Time to platelet count normalization was longest in the LA cohort (p = 0.013). There were no significant between-group differences in bleeding events. Because we are unable to predict which patients will develop refractoriness, we recommend frontline administration of caplacizumab to all patients with iTTP.

Outcomes of thrombotic thrombocytopenic purpura patients submitted to therapeutic plasma exchange in a single center in Brazil

INTRODUCTION

Immune thrombotic thrombocytopenic purpura (iTTP) is characterized by acute systemic microvascular thrombosis and is associated with a high morbidity and mortality, especially in delayed diagnosis (later than 6-7 days from symptoms). iTTP data in Brazil is scarce, so we aimed to characterize the clinical presentation and identify predictors of death risk in patients with this disease in Brazil.

METHODS

In this single-center retrospective study the patients who underwent therapeutic plasma exchange (TPE) for presumptive or confirmed iTTP were evaluated regarding the epidemiological, clinical, laboratorial characteristics and management.

RESULTS

A total of 50 patients (90 % female), with median age (IQR) of 34.1 (27-47) years, were enrolled, of which 12 (24 %) died. The most frequent symptoms were neurological (96 %), bleeding (76 %), gastrointestinal (52 %), fever (38 %), and cardiovascular (22 %). Neurological focal deficit and cardiovascular symptoms were more frequently observed in the non-survivor group (P = 0.0019 and P = 0.007, respectively). The mean ± SD number of days from beginning of symptoms to first TPE was 12.22 ± 7.91. We identified an association regarding mortality rate with a score MITS ≥ 2 points (P = 0.04), a higher indirect bilirubin (P = 0.0006), a higher number of transfused red blood cell units (P = 0.025), and platelet transfusion (P = 0.027).

CONCLUSION

Delayed diagnosis appears to be associated with a higher frequency of neurological symptoms and mortality. Intensity of hemolysis and signs of organ ischemia, such as cardiovascular symptoms and focal neurological deficit, are indicators of death risk.

Real-World Data on Effectiveness and Safety of First-Line Use of Caplacizumab in Italian Centers for the Treatment of Thrombotic Thrombocytopenic Purpura: The Roscapli Study

Background/Objectives: Immune thrombotic thrombocytopenic purpura (iTTP) is a thrombotic microangiopathy caused by the formation of anti-ADAMTS13 antibodies. Caplacizumab is approved for the treatment of acute episodes of iTTP in conjunction with plasma exchange (PEX) and immunosuppression. Real-world data for the use of caplacizumab in Italy have been recently published by a limited number of centers located in the northern and middle regions of the country only. Methods: A total of 38 patients with iTTP were enrolled in the study in six Italian centers spread over the entire territory of the country. The patients' data were registered in eCRF. Results: All patients achieved normalization of platelet count (median 2.0 days, IQR: 2-4), within a time significantly shorter than in the absence of caplacizumab, as previously reported in other studies. As to the secondary aims, patients treated with caplacizumab had a few exacerbations (4/38 (10.5%)) and relapses (2/38, 5.3%). No deaths or refractoriness were observed in these patients. The total length of hospitalization was 12 days (IQR: 9-18) and only one patient required 2 days of stay in the intensive care unit. Interestingly, when caplacizumab was initiated within the first 3 days, the plasma exchange (PEX) duration was 9 days (IQR: 8-10), which was significantly lower than those reported in previous studies conducted in the absence of caplacizumab. No severe adverse event was described in the caplacizumab-treated patients. Conclusions: Caplacizumab reduced exacerbations and refractoriness compared with previously reported standard-of-care regimens. When administered in association with PEX and immunosuppressive therapy, caplacizumab provided rapid normalization of platelet count, which was responsible for lower overall hospitalization time, ICU stay, lower exacerbations and relapses compared to previously reported outcomes of studies carried out without caplacizumab.

Management of immune thrombotic thrombocytopenic purpura without therapeutic plasma exchange

ABSTRACT

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening autoimmune disorder caused by a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS13) deficiency. Caplacizumab, an anti-von Willebrand factor nanobody, is approved for iTTP treatment, reducing the need for therapeutic plasma exchange (TPE) and improving platelet count recovery and survival. We conducted a retrospective study on 42 acute iTTP cases in Austria and Germany, treated with a modified regimen aimed at avoiding TPE if platelet count increased after the first caplacizumab dose. Baseline characteristics and patient outcomes were compared with a control group of 59 patients with iTTP receiving frontline treatment with TPE, caplacizumab, and immunosuppression. The main outcome was the time to platelet count normalization. Secondary outcomes included clinical response, exacerbation, refractory iTTP, iTTP-related deaths, and the time to platelet count doubling. The median time to platelet count normalization was similar between the 2 cohorts (3 and 4 days; P = .31). There were no significant differences in clinical response, exacerbations, refractoriness, iTTP-related deaths, or time to platelet count doubling, reflecting the short-term treatment response. Four patients did not respond to the first caplacizumab dose, and TPE was subsequently initiated. Cytomegalovirus infection, HIV/hepatitis B virus coinfection, an ovarian teratoma with associated antiplatelet antibodies, and multiple platelet transfusions before the correct diagnosis may have impeded the immediate treatment response in these patients. In conclusion, caplacizumab and immunosuppression alone, without TPE, rapidly controlled thrombotic microangiopathy and achieved a sustained clinical response in iTTP. Our study provides a basis for TPE-free iTTP management in experienced centers via shared decision-making between patients and treating physicians.

Adolescence-onset atypical hemolytic uremic syndrome: is it different from infant-onset?

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare, mostly complement-mediated thrombotic microangiopathy. The majority of patients are infants. In contrast to infantile-onset aHUS, the clinical and genetic characteristics of adolescence-onset aHUS have not been sufficiently addressed to date.

METHODS

A total of 28 patients (21 girls, 7 boys) who were diagnosed as aHUS between the ages of ≥10 years and <18 years were included in this study. All available data in the Turkish Pediatric aHUS registry were collected and analyzed.

RESULTS

The mean age at diagnosis was 12.8±2.3 years. Extra-renal involvement was noted in 13 patients (46.4%); neurological involvement was the most common (32%). A total of 21 patients (75%) required kidney replacement therapy. Five patients (17.8%) received only plasma therapy and 23 (82%) of the patients received eculizumab. Hematologic remission and renal remission were achieved in 25 (89.3%) and 17 (60.7%) of the patients, respectively. Compared with the infantile-onset aHUS patients, adolescent patients had a lower complete remission rate during the first episode (p = 0.002). Genetic analyses were performed in all and a genetic variant was detected in 39.3% of the patients. The mean follow-up duration was 4.9±2.6 years. At the last visit, adolescent patients had lower eGFR levels (p = 0.03) and higher rates of chronic kidney disease stage 5 when compared to infantile-onset aHUS patients (p = 0.04).

CONCLUSIONS

Adolescence-onset aHUS is a rare disease but tends to cause more permanent renal dysfunction than infantile-onset aHUS. These results may modify the management approaches in these patients.

[Lupus nephritis and associated thrombotic microangiopathy]

Lupus nephritis represents the most common manifestation of lupus of the solid organs and is associated with an increased risk of chronic kidney disease. The co-occurrence of lupus nephritis and thrombotic microangiopathy is described to be rare but implies the risk of fatal organ dysfunction. We report three patients in whom these two disease entities occurred in parallel, necessitating intensive immunosuppressive therapy, including complement blockade.

Vitamin B12 deficiency misdiagnosed as TTP: What can we learn from it?

The case report by Dwyre et al. shows that vitamin B12 deficiency may be misdiagnosed as acute thrombotic thrombocytopenic purpura. Together with similar observations, this underlines that acquired vitamin B12 deficiency-besides the inherited disorder of intracellular cobalamin metabolism, cbl C disease-should be listed as a separate entity of the thrombotic microangiopathies. Commentary on: Dwyre et al. Microangiopathic thrombocytopenia caused by vitamin B12 deficiency responding to plasma exchange. Br J Haematol 2024; 205:1546-1550.

Thrombotic thrombocytopenic purpura: 100 years of research on Moschcowitz syndrome

ABSTRACT

In the 100 years since Eli Moschcowitz reported the first case of thrombotic thrombocytopenic purpura (TTP), there has been remarkable awareness and progress in the diagnosis and management of this rare blood disorder. This progress initially was the result of careful clinical observations followed by well thought-out therapeutic interventions, with dual goals of both improving outcomes and discerning the pathophysiology of TTP. The discovery of the ADAMTS13 protease set in motion the efforts to more accurately define the specific etiologies of thrombotic microangiopathies (TMAs) based on objective, scientific data rather than clinical characterizations alone. This accurate differentiation led to better and more revealing clinical trials and advancements in the treatment of TTP and other TMAs. Further advances followed and included improvements in immune-suppressive therapy and targeted therapies of immune-mediated TTP (iTTP; caplacizumab) and congenital TTP (cTTP; recombinant ADAMTS13). The longitudinal study of patients with TTP revealed the unexpected risk for long-term complications in both patients with iTTP and those with cTTP in remission. Ongoing studies aim to further understand the prevalence, mechanisms, and appropriate screening for these mood disorders, neurocognitive deficits, and cardiovascular complications that develop at remarkably high rates and are associated with a decreased life expectancy. These discoveries are a result of the collaborative efforts of investigators worldwide that have been fostered by the frequent interactions of investigators via the International TTP Working Group meetings and TMA workshops held regularly at international meetings. These efforts will support the rapid pace of discovery and improved understanding of this rare disease.

Identification of HLA alleles involved in immune thrombotic thrombocytopenic purpura patients from Turkey

Thrombotic thrombocytopenic purpura (TTP) is one of the rare group disorders classified as thrombotic microangiopathies (TMAs). Approximately 90% of TTP developed immune-mediation by the formation of antibodies against the enzyme ADAMTS-13. The exact cause is unknown. To establish an association between human leukocyte antigen (HLA) and autoimmune basis, as susceptibility or protection against the disease, we contributed a study aiming to evaluate the role of HLA in immune-mediated TTP (iTTP). Considering epidemiological factors such as age, sex, ethnicity, and geographical origins, we contributed the study in our country, Turkey, which consist of a very heterogeneous population. Patients' data collection was retrospectively from electronic database on two University hospitals having big therapeutic apheresis service. Control arm was healthy people registered as stem cell donors matched in terms of age and sex. The frequency of HLA-DRB1 and HLA-DQB1 alleles between acquired TTP and the control group was compared using the chi-square method. Yates correction and logistic regression were performed on these results. A total of 75 iTTP patients and 150 healthy individuals enrolled to the study. HLA-DRB1∗11, HLA-DQB1∗03, HLA-DRB1∗11:01, HLA-DRB1∗14:01, HLA-DRB1∗13:05, HLA-DRB1∗11 + HLA-DQB1∗03 allele pair and HLA-DRB1∗15 + HLA- DQB1∗06 were proved to be susceptibility allele pairs for iTTP. HLA-DRB1∗15, HLA-DRB1∗01:01, HLA-DRB1∗07:01, HLA-DRB1∗13:01, HLA-DRB1∗14:54, HLA-DQB1∗05:01, HLA-DQB1∗02:02 and HLA-DRB1∗07 + HLA-DQB1∗02 allele pair were found to be protective against iTTP. Our findings support an association with iTTP across very heterogenous populations in Turkey.

Clinical, biological, prognostic characteristics of patients with immune-mediated thrombotic thrombocytopenic purpura and Sjögren's disease

OBJECTIVES

The association between immune-mediated thrombotic thrombocytopenic purpura (iTTP) and Sjögren disease (SjD) has been poorly investigated. This study presents the first retrospective cohort of iTTP-SjD aiming to identify risk factors for iTTP occurrence in SjD patients and examine their clinical course.

METHODS

Patients with iTTP-SjD were identified within the French TTP Registry based on American College of Rheumatology/European League Against Rheumatism 2016 criteria. A comparative analysis was conducted with two control groups comprising primary SjD (pSjD) patients from the French ASSESS cohort and idiopathic iTTP patients from the French TTP Registry. Demographic, clinical and biological data were retrospectively collected.

RESULTS

Thirty iTTP-SjD patients were included and compared with 65 pSjD and 45 idiopathic iTTP patients. The majority of iTTP-SjD patients (n=18) were diagnosed with SjD at the time of iTTP diagnosis. In comparison with the pSjD cohort, iTTP-SjD patients were diagnosed with SjD at a younger age (p=0.039) and showed a higher prevalence of anti-SjS-related antigen A antibody positivity and xerostomia (p=0.015, p=0.035, respectively). EULAR Sjogren's Syndrome Disease Activity Index showed similar activity levels between the two groups. iTTP-SjD patients were treated with plasma exchange (n=28), corticosteroids, rituximab (n=19) and caplacizumab (n=3). In comparison with the idiopathic iTTP cohort, mortality rates (log-rank tests, p=0.228), biological and clinical iTTP relapses (multivariate analysis, p=0.181) were comparable and short-term outcomes (survival at day 30, relapse) were favourable.

CONCLUSION

iTTP can be a rare complication in patients with SjD. Further studies involving larger cohorts and long-term follow-up are warranted to confirm these findings and to explore the efficacy of immunomodulators and caplacizumab in iTTP-SjD patients.

Characteristics of anti-melanoma differentiation associated gene 5 antibody-positive dermatomyositis with thrombotic microangiopathy

OBJECTIVES

Anti-melanoma differentiation associated gene 5 antibody (anti-MDA5 Ab)-positive dermatomyositis (DM) is a representative of rapidly progressive interstitial pneumonia. However, its association with thrombotic microangiopathy (TMA), characterized by thrombocytopenia, haemolytic anaemia, and organ dysfunction, has not been defined. This study aimed to elucidate the characteristics of anti-MDA5 Ab-positive DM accompanied by TMA.

METHODS

We reviewed our hospital records from November 2009 to September 2022. We included patients in accordance with the 2017 European League Against Rheumatism/American College of Rheumatology classification criteria and the criteria of Bohan and Peter. TMA was diagnosed according to the criteria for transplantation-associated TMA proposed by the International Working Group.

RESULTS

This study enrolled a total of 26 anti-MDA5 Ab-positive DM patients, four of whom developed TMA. The patients with TMA had an increased urine protein/creatinine ratio. In addition, these four of them showed significantly elevated levels of ferritin and anti-MDA5 Ab titers and were considered to have high disease activity; yet, all of them survived.

CONCLUSIONS

Our study indicated that anti-MDA5 Ab-positive DM patients with hyperferritinemia, a high anti-MDA5 Ab titer, and an increased urine protein/creatinine ratio should be carefully managed, bearing in mind a complication of TMA.

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.

Diagnostic Challenges in a Case of Immune-Mediated Thrombotic Thrombocytopenic Purpura With Severe ADAMTS13 Deficiency

Thrombotic Thrombocytopenic Purpura (TTP) is rare and potentially life-threatening thrombotic microangiopathy (TMA) caused by acquired immune-mediated or congenital deficiency of the von Willebrand factor regulatory enzyme, a Disintegrin And Metalloproteinase with a Thrombospondin Type 1 motif, member 13 (ADAMTS13) which cause microthrombi to form and occlude the microvasculature. The occurrence of acute kidney injury (AKI) in TTP is rare and often underestimated due to confusion with hemolytic uremic syndrome (HUS). A 23-year-old Mestizo male patient presented with altered mental status, hemolytic anemia, thrombocytopenia, intermittent fever, laboratory tests suggestive of thrombotic microangiopathy, and clinical findings consistent with acute kidney injury. Predictive values of the platelet count, lactate dehydrogenase, absent active cancer, schistocytes, mean corpuscular volume, international normalized ratio, creatinine (PLASMIC) score, were used to assess the likelihood of ADAMTS13 deficiency, were employed, and enzymatic activity testing confirmed severe protein deficiency. Honduras' lack of advanced diagnostic capabilities is underscored, emphasizing the urgent need to invest in precision medical technology. ADAMTS13 testing allows for a more precise diagnosis of TTP, which is crucial for early diagnosis and timely treatment.

Thrombotic Microangiopathy in Pregnancy: Current Understanding and Management Strategies

Thrombotic microangiopathy (TMA) represents a heterogeneous group of disorders characterized by microvascular thrombosis and end-organ damage. Pregnancy-associated thrombotic microangiopathy (p-TMA) has emerged as a distinct clinical entity with unique diagnostic challenges. Identifying the specific form of p-TMA is critical for appropriate and timely management. This review offers a comprehensive overview of the various forms of thrombotic microangiopathies associated with pregnancy, highlighting our current understanding of their pathophysiology and the evolving landscape of diagnosis and treatment for each.

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.

Practical approach to thrombocytopenia in patients with sepsis: a narrative review

Thrombocytopenia frequently occurs in patients with sepsis. Disseminated intravascular coagulation (DIC) may be a possible cause of thrombocytopenia owing to its high prevalence and association with poor outcomes; however, it is important to keep the presence of other diseases in mind in sepsis practice. Thrombotic microangiopathy (TMA), which is characterized by thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (HUS), and complement-mediated HUS, is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ damage. TMA has become widely recognized in recent years because of the development of specific treatments. Previous studies have reported a remarkably lower prevalence of TMA than DIC; however, its epidemiology is not well defined, and there may be cases in which TMA is not correctly diagnosed, resulting in poor outcomes. Therefore, it is important to differentiate DIC from TMA. Nevertheless, differentiating between DIC and TMA remains a challenge as indicated by previous reports that most patients with TMA can be diagnosed as DIC using the universal coagulation scoring system. Several algorithms to differentiate sepsis-related DIC from TMA have been suggested, contributing to improving the care of septic patients with thrombocytopenia; however, it may be difficult to apply these algorithms to patients with coexisting DIC and TMA, which has recently been reported. This review describes the disease characteristics, including epidemiology, pathophysiology, and treatment, of DIC, TMA, and other diseases with thrombocytopenia and proposes a novel practical approach flow, which is characterized by the initiation of the diagnosis of TMA in parallel with the diagnosis of DIC. This practical flow also refers to the longitudinal diagnosis and treatment flow with TMA in mind and real clinical timeframes. In conclusion, we aim to widely disseminate the results of this review that emphasize the importance of incorporating consideration of TMA in the management of septic DIC. We anticipate that this practical new approach for the diagnostic and treatment flow will lead to the appropriate diagnosis and treatment of complex cases, improve patient outcomes, and generate new epidemiological evidence regarding TMA.

[Lupus nephritis and thrombotic microangiopathy: A review]

Lupus nephritis (LN) is one of the most common organ-specific manifestations of systemic lupus erythematosus (SLE). Various clinical signs of LN develop in at least 50% of patients with SLE. In addition to LN, the spectrum of renal lesions associated with SLE also includes vascular pathology. One of the variants of renal microvascular injury is thrombotic microangiopathy (TMA), the mechanisms of which are diverse. The review focuses on the main forms of TMA, including antiphospholipid syndrome and nephropathy associated with antiphospholipid syndrome, TMA caused by complement system regulation disorders and deficiency of ADAMTS13. In most cases, these forms of TMA are combined with LN. However, they may also exist as a single form of kidney damage. This article discusses the TMA pathogenesis, the impact on kidney prognosis, and treatment options.

Peak ADAMTS13 activity to assess ADAMTS13 conformation and risk of relapse in immune-mediated thrombotic thrombocytopenic purpura

ABSTRACT

Previous studies have demonstrated that >38% of patients with immune-mediated thrombotic thrombocytopenic purpura in remission with activity >50% had an open ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13) conformation. We assessed ADAMTS13 conformation in remission (ADAMTS13 activity >60%), focusing on peak ADAMTS13 activity levels and longitudinal assessment in 420 samples across 157 patients. Fewer cases had an open conformation at peak ADAMTS13 activity than unselected remission samples with ADAMTS13 activity >60% (23% vs 43%). Patients with a closed ADAMTS13 conformation at peak ADAMTS13 activity had an eightfold lower relapse rate in the subsequent year (9% vs 46%) and a fivefold lower relapse rate within 2 years (23% vs 62%) compared with cases with an open conformation. Patients with an open conformation at peak ADAMTS13 activity required preemptive anti-CD20 treatment earlier than those with a closed conformation (median, 10 vs 25 months). Longitudinally, an open conformation was evident at, and often preceded relapse. When the conformation was already open before relapse, an increase in the conformation index at relapse was seen despite the undetectable anti-ADAMTS13 immunoglobulin G (IgG) antibody. In cases with detectable anti-ADAMTS13 IgG antibody, these became undetectable before achieving a closed conformation, highlighting the relapse risk even with undetectable anti-ADAMTS13 IgG antibody and the clinical utility of open/closed during monitoring. To our knowledge, this is the first study to show an association between relapse risk and ADAMTS13 conformation when activity levels are at a peak. The open conformation identifies antibody-mediated subclinical disease that is not detectable by the current ADAMTS13 testing.

Schistocyte detection in artificial intelligence age

Schistocytes are fragmented red blood cells produced as a result of mechanical damage to erythrocytes, usually due to microangiopathic thrombotic diseases or mechanical factors. The early laboratory detection of schistocytes has a critical impact on the timely diagnosis, effective treatment, and positive prognosis of diseases such as thrombocytopenic purpura and hemolytic uremic syndrome. Due to the rapid development of science and technology, laboratory hematology has also advanced. The accuracy and efficiency of tests performed by fully automated hematology analyzers and fully automated morphology analyzers have been considerably improved. In recent years, substantial improvements in computing power and machine learning (ML) algorithm development have dramatically extended the limits of the potential of autonomous machines. The rapid development of machine learning and artificial intelligence (AI) has led to the iteration and upgrade of automated detection of schistocytes. However, along with significantly facilitated operation processes, AI has brought challenges. This review summarizes the progress in laboratory schistocyte detection, the relationship between schistocytes and clinical diseases, and the progress of AI in the detection of schistocytes. In addition, current challenges and possible solutions are discussed, as well as the great potential of AI techniques for schistocyte testing in peripheral blood.

Thrombotic microangiopathy in patients with sickle cell disease

OBJECTIVE

To describe two cases of patients who had thrombotic microangiopathy (TMA) associated with sickle cell disease (SCD).

CASE DESCRIPTION

Both patients started with a painful crisis and had acute chest syndrome during hospitalization. They showed significant worsening of hemolytic anemia, with very high levels of lactate dehydrogenase, thrombocytopenia, lowered level of consciousness, organ damage and the presence of schistocytes in peripheral blood. Due to the possibility of TMA, despite the very rare association with SCD, they were treated with fresh frozen plasma replacement and plasmapheresis, with good response.

COMMENTS

TMA is a serious, life-threatening disease, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ damage. The association of SCD and TMA is difficult to diagnose, since they can share a similar clinical presentation. Recognizing this association and promptly instituting treatment may impact the survival of these patients.

Recombinant ADAMTS13 in Congenital Thrombotic Thrombocytopenic Purpura

BACKGROUND

Congenital thrombotic thrombocytopenic purpura (TTP) results from severe hereditary deficiency of ADAMTS13. The efficacy and safety of recombinant ADAMTS13 and standard therapy (plasma-derived products) administered as routine prophylaxis or on-demand treatment in patients with congenital TTP is not known.

METHODS

In this phase 3, open-label, crossover trial, we randomly assigned patients in a 1:1 ratio to two 6-month periods of prophylaxis with recombinant ADAMTS13 (40 IU per kilogram of body weight, administered intravenously) or standard therapy, followed by the alternate treatment; thereafter, all the patients received recombinant ADAMTS13 for an additional 6 months. The trigger for this interim analysis was trial completion by at least 30 patients. The primary outcome was acute TTP events. Manifestations of TTP, safety, and pharmacokinetics were assessed. Patients who had an acute TTP event could receive on-demand treatment.

RESULTS

A total of 48 patients underwent randomization; 32 completed the trial. No acute TTP event occurred during prophylaxis with recombinant ADAMTS13, whereas 1 patient had an acute TTP event during prophylaxis with standard therapy (mean annualized event rate, 0.05). Thrombocytopenia was the most frequent TTP manifestation (annualized event rate, 0.74 with recombinant ADAMTS13 and 1.73 with standard therapy). Adverse events occurred in 71% of the patients with recombinant ADAMTS13 and in 84% with standard therapy. Adverse events that were considered by investigators to be related to the trial drug occurred in 9% of the patients with recombinant ADAMTS13 and in 48% with standard therapy. Trial-drug interruption or discontinuation due to adverse events occurred in no patients with recombinant ADAMTS13 and in 8 patients with standard therapy. No neutralizing antibodies developed during recombinant ADAMTS13 treatment. The mean maximum ADAMTS13 activity after recombinant ADAMTS13 treatment was 101%, as compared with 19% after standard therapy.

CONCLUSIONS

During prophylaxis with recombinant ADAMTS13 in patients with congenital TTP, ADAMTS13 activity reached approximately 100% of normal levels, adverse events were generally mild or moderate in severity, and TTP events and manifestations were rare. (Funded by Takeda Development Center Americas and Baxalta Innovations; ClinicalTrials.gov number, NCT03393975.).

ADAMTS13 recovery in acute thrombotic thrombocytopenic purpura after caplacizumab therapy

ABSTRACT

Caplacizumab prevents the interaction between von Willebrand factor and platelets and is used to treat immune thrombotic thrombocytopenic purpura (iTTP). Its administration has been associated with a delay in ADAMTS13 activity restoration after plasma exchange (PEX) suspension. We analyzed the outcomes of 113 iTTP episodes, 75 of which were treated with caplacizumab, in 108 patients from the Spanish Registry of Thrombotic Thrombocytopenic Purpura. Caplacizumab shortened the time to platelet count normalization and reduced PEX requirement, exacerbations, and relapses. There was no difference in the time to achieve ADAMTS13 activity ≥20% after PEX end between caplacizumab-treated and nontreated episodes (median [interquartile range], 14.5 [7.7-27.2] vs 13.0 [8.0-29.0] days, P = .653). However, considering the 36 episodes in which caplacizumab was started ≤3 days after iTTP diagnosis, the time for ADAMTS13 restoration from PEX end was higher than in those episodes in which caplacizumab was started >3 days after iTTP diagnosis (20.0 [12.0-43.0] vs 11.0 [3.5-20.0] days, P = .003) or than in non-caplacizumab-treated episodes (P = .033). This finding could be related to a significantly shorter duration of PEX in early caplacizumab-treated episodes than in late caplacizumab-treated episodes (5.5 [4.0-9.0] vs 15.0 [11.0-21.5] days, P < .001) or non-caplacizumab-treated episodes (11.0 [6.0-26.0] days, P < .001). There were no differences in time to ADAMTS-13 restoration from PEX start (28.0 [17.2-47.5], 27.0 [19.0-37.5] and 29.5 [15.2-45.0] days in early caplacizumab-treated, late caplacizumab-treated and non-caplacizumab-treated episodes). Early administered caplacizumab does not prevent the requirement for immunosuppression but has beneficial effects by shortening PEX requirement without major safety concerns.

Assessment of epidemiology and outcomes of adult patients with kidney-limited thrombotic microangiopathies

Thrombotic microangiopathies (TMA) are usually associated with hematological features (RH-TMA). The epidemiology of TMA limited to kidneys (RL-TMA) is unclear Therefore, patients with TMA and native kidney biopsies were identified during 2009-2022 in 20 French hospitals and results evaluated. RL-TMA was present in 341/757 (45%) patients and associated with lower creatinine levels (median 184 vs 346 μmol/L) than RH-TMA. RL-TMA resulted from virtually all identified causes, more frequently from anti-VEGF treatment and hematological malignancies but less frequently from shigatoxin-associated hemolytic uremic syndrome (HUS), systemic sclerosis, gemcitabine and bacterial infection, and even less frequently when three or more causes/triggers were combined (RL-TMA: 5%; RH-TMA: 12%). RL-TMA was associated with significantly lower major cardiovascular events (10% vs 20%), kidney replacement therapy (23% vs 43%) and death (12% vs 20%) than RH-TMA during follow-up (median 28 months). Atypical HUS (aHUS) was found in 326 patients (RL-TMA: 43%, RH-TMA: 44%). Among the 69 patients with proven complement-mediated aHUS, eculizumab (anti-C5 therapy) was used in 43 (62%) (RL-TMA: 35%; RH-TMA: 71%). Among the 257 other patients with aHUS, including 51% with RL-TMA, eculizumab was used in 29 but with unclear effects of this treatment. Thus, RL-TMA represents a very high proportion of patients with TMA and results from virtually all known causes of TMA and includes 25% of patients with complement-mediated aHUS. Adverse outcomes of RL-TMA are lower compared to RH-TMA but remain significant. Anti-C5 therapy was rarely used in RL-TMA, even in proven complement-mediated aHUS, and its effects remain to be assessed.

How We Interpret Thrombosis with Thrombocytopenia Syndrome?

Platelets play an important role in hemostasis, and a low platelet count usually increases the risk of bleeding. Conditions in which thrombosis occurs despite low platelet counts are referred to as thrombosis with thrombocytopenia syndrome, including heparin-induced thrombocytopenia, vaccine-induced immune thrombotic thrombocytopenia, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, thrombotic microangiopathy (TMA), and disseminated intravascular coagulation. TMA includes thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (HUS), and atypical HUS. Patients with these pathologies present with thrombosis and consumptive thrombocytopenia associated with the activation of platelets and the coagulation system. Treatment varies from disease to disease, and many diseases have direct impacts on mortality and organ prognosis if therapeutic interventions are not promptly implemented. Underlying diseases and the results of physical examinations and general laboratory tests as part of a thorough workup for patients should promptly lead to therapeutic intervention before definitive diagnosis. For some diseases, the diagnosis and initial treatment must proceed in parallel. Utilization of not only laboratory tests but also various scoring systems is important for validating therapeutic interventions based on clinical information.

ADAMTS-13 conformation influences autoimmune recognition in immune thrombotic thrombocytopenic purpura

BACKGROUND

Patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP) have anti-ADAMTS-13 immunoglobulin G (IgG) autoantibodies that enhance ADAMTS-13 clearance and/or inhibit its function. ADAMTS-13 normally circulates in a closed conformation, which is manifested by the interaction of the CUB domains with the central spacer domain. Disruption of the spacer-CUB interaction opens ADAMTS-13, which augments its proteolytic function but may also expose cryptic autoimmune epitopes that promote further autoantibody recognition.

OBJECTIVES

To explore differences in autoantibody binding to ADAMTS-13 in its closed or open conformations in patients with iTTP and to correlate these differences with disease-related parameters.

METHODS

We developed a novel assay to measure autoantibodies binding to closed and open ADAMTS-13. Autoantibody titer and IgG subclass binding to open or closed ADAMTS-13 were measured in 70 iTTP first presentation samples and correlated with clinical data, remission, and relapse.

RESULTS

In 70 patients with iTTP, the mean autoantibody titer against open ADAMTS-13 was, on average, approximately 2-fold greater than that against closed ADAMTS-13, suggesting that ADAMTS-13 opening increases epitope exposure and immune complex formation. Autoantibody titer against closed/open ADAMTS-13 and IgG subclass did not correlate with ADAMTS-13 antigen at presentation. Two patients with iTTP and persistent autoantibodies lost specificity for closed ADAMTS-13 in remission. Recognition of closed/open ADAMTS-13 and autoantibody IgG subclass between the first and second iTTP episodes were very similar.

CONCLUSION

ADAMTS-13 autoantibody binding is highly influenced by ADAMTS-13 conformation. Although this does not appear to modify the pathogenicity of autoantibodies, the autoantibody signature at relapse suggests that relapse represents re-emergence of the original autoimmune response rather than de novo presentation.

Thrombotic microangiopathy after kidney transplantation: Expanding etiologic and pathogenetic spectra

Thrombotic microangiopathy (TMA) is an uncommon but serious complication that not only affects native kidneys but also transplanted kidneys. This review is specifically focused on post-transplant TMA (PT-TMA) involving kidney transplant recipients. Its reported prevalence in the latter population varies from 0.8% to 14% with adverse impacts on both graft and patient survival. It has many causes and associations, and the list of etiologic agents and associations is growing constantly. The pathogenesis is equally varied and a variety of patho genetic pathways lead to the development of microvascular injury as the final common pathway. PT-TMA is categorized in many ways in order to facilitate its management. Ironically, more than one causes are contributory in PT-TMA and it is often difficult to pinpoint one particular cause in an individual case. Pathologically, the hallmark lesions are endothelial cell injury and intravascular thrombi affecting the microvasculature. Early diagnosis and classification of PT-TMA are imperative for optimal outcomes but are challenging for both clinicians and pathologists. The Banff classification has addressed this issue and has developed minimum diagnostic criteria for pathologic diagnosis of PT-TMA in the first phase. Management of the condition is also challenging and still largely empirical. It varies from simple maneuvers, such as plasmapheresis, drug withdrawal or modification, or dose reduction, to lifelong complement blockade, which is very expensive. A thorough understanding of the condition is imperative for an early diagnosis and quick treatment when the treatment is potentially effective. This review aims to increase the awareness of relevant stakeholders regarding this important, potentially treatable but under-recognized cause of kidney allograft dysfunction.

Stress-induced hyperglycemia is associated with the mortality of thrombotic thrombocytopenic purpura patients

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy with a rapid progression and high mortality rate. We aimed to explore early risk factors for mortality in patients with TTP.

METHODS

We conducted a retrospective analysis of 42 TTP patients that were admitted to our hospital between 2000 and 2021, with a median age of 49 (29-63) years. Risk factors for mortality were evaluated using multivariate logistic regression. Receiver operating characteristic curve analysis was used to determine the cut-off value of glucose for predicting mortality in patients, which was validated by comparison to a similar cohort in the published literature.

RESULTS

Elevated glucose level and reduced red blood cells (RBC) counts were risk factors for mortality in patients with TTP (glucose, odds ratio and 95% confidence interval: 2.476 [1.368-4.484]; RBC, odds ratio and 95% confidence interval: 0.095 [0.011-0.799]). The area under the curve of glucose was 0.827, and the cut-off value was 9.2 mmol/L, with a sensitivity of 75.0% and specificity of 95.8%. A total of 26 cases from the validation cohort had a sensitivity of 71.0% and a specificity of 84.0%. The change trends of the TTP-related laboratory indices differed during hospitalization.

CONCLUSION

Hyperglycemia at admission and unstable blood glucose levels during hospitalization may be potential predictors of mortality for TTP patients. The improved prognosis was associated with the recovery of platelet counts and a significant decrease in serum lactate dehydrogenase after five days of treatment.

HELLP Syndrome and Differential Diagnosis with Other Thrombotic Microangiopathies in Pregnancy

Thrombotic microangiopathies (TMAs) comprise a distinct group of diseases with different manifestations that can occur in both pediatric and adult patients. They can be hereditary or acquired, with subtle onset or a rapidly progressive course, and they are particularly known for their morbidity and mortality. Pregnancy is a high-risk time for the development of several types of thrombotic microangiopathies. The three major syndromes are hemolysis, elevated liver function tests, and low platelets (HELLP); hemolytic uremic syndrome (HUS); and thrombotic thrombocytopenic purpura (TTP). Because of their rarity, clinical information and therapeutic results related to these conditions are often obtained from case reports, small series, registries, and reviews. The collection of individual observations, the evolution of diagnostic laboratories that have identified autoimmune and/or genetic abnormalities using von Willebrand factor post-secretion processing or genetic-functional alterations in the regulation of alternative complement pathways in some of these TMAs, and, most importantly, the introduction of advanced treatments, have enabled the preservation of affected organs and improved survival rates. Although TMAs may show different etiopathogenesis routes, they all show the presence of pathological lesions, which are characterized by endothelial damage and the formation of thrombi rich in platelets at the microvascular level, as a common denominator, and thrombotic damage to microcirculation pathways induces "mechanical" (microangiopathic) hemolytic anemia, the consumption of platelets, and ischemic organ damage. In this review, we highlight the current knowledge about the diagnosis and management of these complications during pregnancy.

Bortezomib in relapsed/refractory immune thrombotic thrombocytopenic purpura: A single-centre retrospective cohort and systematic literature review

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening haematological condition. Initial treatment involves plasma exchange (PLEX), corticosteroids, caplacizumab and rituximab. In relapsed and refractory cases despite initial treatments, further immune-modulating therapy includes the proteasome inhibitor, bortezomib. Evidence for bortezomib in this setting is limited to case reports and case series. We report our experience and perform a systematic review of the literature. We identified 21 publications with 28 unique patients in addition to our cohort of eight patients treated with bortezomib. The median age of patients was 44 years (IQR: 27-53) and 69% female. They were usually in an initial, refractory presentation of iTTP where they had received PLEX, corticosteroids, rituximab and another line of therapy. After bortezomib administration, 72% of patients had a complete response, with 85% maintaining a durable response without relapse at the last follow-up.

Clinical Evaluation and Management of Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) refers to a diverse group of diseases that share clinical and histopathologic features. TMA is clinically characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and organ injury that stems from endothelial damage and vascular occlusion. There are several disease states with distinct pathophysiological mechanisms that manifest as TMA. These conditions are associated with significant morbidity and mortality and require urgent recognition and treatment. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are traditionally considered to be primary forms of TMA, but TMA more commonly occurs in association with a coexisting condition such as infection, pregnancy, autoimmune disease, or malignant hypertension, among others. Determining the cause of TMA is a diagnostic challenge because of limited availability of disease-specific testing. However, identifying the underlying etiology is imperative as treatment strategies differ. Our understanding of the conditions that cause TMA is evolving. Recent advances have led to improved comprehension of the varying pathogenic mechanisms that drive TMA. Development of targeted therapeutics has resulted in significant improvements in patient outcomes. In this article, we review the pathogenesis and clinical features of the different TMA-causing conditions. We outline a practical approach to diagnosis and management and discuss empiric and disease-specific treatment strategies.

Alterations in the von Willebrand factor/ADAMTS-13 axis in preeclampsia

BACKGROUND

Preeclampsia is a gestational hypertensive disorder characterized by maternal endothelial activation and increased ratio of soluble fms-like tyrosine kinase-1 (sFlt-1) inhibitor to placental growth factor (PlGF). The von Willebrand factor (VWF)/ADAMTS-13 axis is of interest because of the underlying endothelial activation and clinical overlap with pregnancy-associated thrombotic thrombocytopenic purpura.

OBJECTIVES

To assess VWF, ADAMTS-13, and VWF/ADAMTS-13 ratio in preeclampsia and look for associations with sFlt-1/PlGF ratio and clinical features.

METHODS

Thirty-four preeclampsia cases and 48 normal pregnancies were assessed in a case-control study. Twelve normal pregnancies in women with a history of preeclampsia formed an additional comparator group. VWF antigen (VWF:Ag) and VWF activity (VWF:Ac [VWF:glycoprotein IbM]) were measured via automated immunoturbidimetric assay, ADAMTS-13 activity was measured via fluorescence resonance energy transfer-VWF73 assay, and sFlt-1 and PlGF were measured via enzyme-linked immunosorbent assay.

RESULTS

VWF:Ag was higher in preeclampsia than in normal pregnancy (median, 3.07 vs 1.87 IU/mL; P < .0001). ADAMTS-13 activity was slightly lower (median, 89.6 vs 94.4 IU/dL; P = .02), with no severe deficiencies. Significant elevations in VWF:Ac were not observed in preeclampsia, resulting in reduced VWF:Ac/VWF:Ag ratios (median, 0.77 vs 0.97; P < .0001). VWF:Ag/ADAMTS-13 ratios were significantly higher in preeclampsia (median, 3.42 vs 2.06; P < .0001), with an adjusted odds ratio of 19.2 for a ratio of >2.7 (>75th centile of normal pregnancy). Those with a history of preeclampsia had similar ratios to normal pregnant controls. VWF:Ag/ADAMTS-13 and sFlt-1/PlGF were not correlated. However, percentage reduction in platelets correlated positively with VWF:Ac (P = .01), VWF:Ac/VWF:Ag ratio (P = .004), and sFlt-1/PlGF ratio (P = .01).

CONCLUSION

The VWF/ADAMTS-13 axis is significantly altered in preeclampsia. Further investigation of potential clinical utility is warranted.

Clinical characteristics of anti-GBM disease with thrombotic microangiopathy: a case report and literature review

The coexistence of anti-glomerular basement membrane (anti-GBM) disease with thrombotic microangiopathy (TMA) is rarely encountered, and the clinical characteristics of this phenomenon are not well known.A 76-year-old Japanese woman with a history of idiopathic pulmonary disease was diagnosed with anti-GBM disease due to rapidly progressive glomerulonephritis and a positive anti-GBM antibody test result. We treated the patient with hemodialysis, glucocorticoids, and plasmapheresis. During treatment, the patient suddenly became comatose. TMA was then diagnosed because of thrombocytopenia and microangiopathic hemolytic anemia. The activity of a disintegrin-like and metalloproteinase with thrombospondin type 1 motif 13 (ADAMTS-13) was retained at 48%. Although we continued the treatment, the patient died of respiratory failure. An autopsy revealed the cause of respiratory failure to be an acute exacerbation of interstitial pneumonia. The clinical findings of the renal specimen indicated anti-GBM disease; however, there were no lesions suggestive of TMA. A genetic test did not reveal an apparent genetic mutation of the atypical hemolytic uremic syndrome.We conducted a literature review of past case reports of anti-GBM disease with TMA. The following clinical characteristics were obtained. First, 75% of the cases were reported in Asia. Second, TMA tended to appear during the treatment course for anti-GBM disease and usually resolved within 12 weeks. Third, ADAMTS-13 activity was retained above 10% in 90% of the cases. Fourth, central nervous system manifestations occurred in more than half of the patients. Fifth, the renal outcome was very poor. Further studies are required to understand the pathophysiology of this phenomenon.

Longitudinal characterization of symptoms, healthcare resource utilization, and costs among people with thrombotic thrombocytopenic purpura compared with non-thrombotic thrombocytopenic purpura controls

AIMS

Thrombotic thrombocytopenic purpura (TTP) is an ultra-rare blood disorder, characterized by severe ADAMTS13 deficiency. Affected individuals present with potentially life-threatening acute events and may experience sub-acute and chronic TTP manifestations often resulting in long-term organ damage. Incremental symptom prevalence before, during, and after an acute event as well as healthcare resource utilization (HCRU) and costs during and after an acute event were compared between people with TTP and matched non-TTP controls.

METHODS

This retrospective, matched study used data from Merative MarketScan Commercial Database and Medicare Supplemental Database (from January 1, 2008, through September 30, 2021) to identify people with TTP (inpatient diagnosis for "thrombotic microangiopathy (TMA)" or "congenital TTP," and ≥1 claim for plasma exchange or infusion). People with TTP were matched (1:2) with non-TTP controls on age, sex, geographic region, index year, and select Elixhauser comorbidities.

RESULTS

255 people with TTP were matched with 510 non-TTP controls. Both cohorts had a mean age of 43.9 years; 71% were female. Overall, more people with TTP reported symptoms compared with non-TTP controls prior to (51% vs 43%), during (99% vs 52%), and after an acute event (85% vs 50%; p < 0.05 for all periods). Symptom prevalence decreased following an acute event compared with during an acute event, but remained high-85% of people with TTP experienced symptoms compared with 50% of non-TTP controls. HCRU and mean costs per patient per month were significantly higher in all care settings among people with TTP compared with non-TTP controls (p < 0.05).

LIMITATIONS

Identification of patient populations may have been limited due to coding errors, as the data were obtained from an administrative claims database.

CONCLUSIONS

TTP is associated with a substantial symptom burden and increased costs and HCRU during and up to almost a year after acute events, demonstrating the longitudinal burden of this disease.

Thrombotic thrombocytopenic purpura that developed 3 years after systemic lupus erythematosus had remitted with rituximab therapy

Patients with systemic lupus erythematosus (SLE) occasionally develop thrombotic thrombocytopenic purpura (TTP), which can be fatal. Here, we report a case of TTP developing 3 years after SLE remitted with rituximab (RTX) therapy. A 50-year-old woman was treated with RTX for marked immune thrombocytopenic purpura and autoimmune haemolytic anaemia due to SLE relapse. After induction of remission, she was treated with prednisolone alone without maintenance therapy with RTX. Approximately 3 years later, she was readmitted with marked thrombocytopenia and severe renal dysfunction. On admission, she was diagnosed with TTP for the first time based on severe reduction in a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity and detection of ADAMTS13 inhibitors. CD19+ B cells in the patient's serum increased to 34%, suggesting that B cells had reactivated once the effect of RTX had subsided. The patient was successfully treated with plasmapheresis, glucocorticoid pulse therapy, and RTX. There are no previous reports of newly diagnosed TTP with ADAMTS13 inhibitor production after having achieved remission of SLE with RTX. Therefore, our report also discusses the potential mechanisms of production of new autoantibodies after B-cell depletion therapy.

End stage renal disease in patient with microscopic polyangiitis and atypical hemolytic-uremic syndrome arose 3 weeks after the third dose of anti-SARS-CoV2 vaccine mRNA-1273: A case report with literature revision

RATIONALE

Immune system deregulation, including AAV, is a key event that may potentially evolve into ESRD. Abnormal activation of the cAP is also a cardinal feature of TMA, particularly aHUS. The kidney is the most frequently involved organ, and renal-limited forms of TMA are often encountered in clinical practice. Isolated case reports described the occurrence of renal TMA in AAV patients. Some cases of both de novo and relapses of AAV and/or TMAs after anti-SARS-CoV2 vaccination have been reported. We reported, for the 1st time, a case of patients with new-onset MPA and aHUS occurring 3 weeks after the third dose of mRNA-1273 vaccine anti-SARS-CoV2.

PATIENT CONCERNS

We present a 67-year-old man, affected by arterial hypertension, reported, after mRNA-1273 vaccine anti-SARS-CoV2, anuria, fatigue, anorexia and nausea. Laboratory data revealed acute renal failure.

DIAGNOSIS

Positivity of MPO-ANCA was observed. 7 days after admission, we observed a worsening of anemia and thrombocytopenia with haptoglobin reduction, LDH increase and presence of schistocytes. Plasma levels of ADAMTS-13 were normal. A renal biopsy was performed, and findings were consistent with microscopic polyangiitis, with features of micro-thrombotic glomerulopathy. Genetic tests revealed absence of hybrid genes associated with the increased risk of aHUS.

INTERVENTIONS AND OUTCOMES

We started renal replacement treatment, including hemodialysis, and pulsed methylprednisolone, with no improvement of laboratory parameters. Then, plasma exchange was performed leading to partial haematological response. Only with Eculizumab, a human C5 inhibitor, we observed a normalization of haptoglobin levels and platelets' count. However, three months after discharge, the patient still required hemodialysis.

LESSONS

To our knowledge we observed the first case aHUS, without genetic predisposition, associated with MPA occurring after the third dose of anti-SARS-CoV2 vaccine. This case report highlights the potential link between anti-SARS-CoV2 vaccine as a trigger of MPA and aHUS. This systematic review offers additional perspectives. It is plausible to hypothesize that the vaccine was the trigger for the development of these 2 diseases.Solid evidence on the mechanisms of interaction between vaccine and immune system, the role of genetic predisposition, and other variables, will shed additional light on the controversial link between anti-SARS-CoV2 vaccine and autoimmunity.

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.