Diagnosis and treatment of thrombotic microangiopathy

Cancer-Associated Thrombotic Microangiopathy: Literature Review and Report of Five Cases

Thrombotic microangiopathy (TMA) is an anatomopathological lesion mediated by endothelial dysfunction and characterized by the creation of microthrombi in small vessels. In patients with cancer, it may be due to toxicity secondary to chemotherapy, tumor embolization, or hematopoietic progenitor transplantation. Cancer-associated TMA is an underestimated entity that generally appears in the final stages of the disease, although it may also be the initial manifestation of an underlying cancer. Support treatment is necessary in all cases and, depending on the cause, different targeted therapies may be used. The prognosis is very poor. In this article we present a comprehensive review of the existing literature on the physiological mechanisms of cancer-associated TMA. Afterwards, five clinical cases will be presented of patients who developed TMA and were diagnosed in our Department in 2023. We present a discussion of the different causes that triggered the condition, the possible reasons behind the underestimation of this pathology, and the measures that may be adopted.

Clinical features, treatment, and outcomes of patients with carfilzomib induced thrombotic microangiopathy

BACKGROUND

Thrombotic microangiopathy (TMA) is associated with carfilzomib, and knowledge of carfilzomib-induced TMA is based mainly on case reports. This study investigated the clinical characteristics of patients with carfilzomib-induced TMA and provided a reference for the rational use of carfilzomib.

METHODS

Reports of carfilzomib-induced TMA were collected for retrospective analysis by searching the Chinese and English databases from inception to January 31, 2024.

RESULTS

Sixty-six patients were included, with a median age of 63 years (range 39, 85). The median time to onset of TMA was 42 days (range 1, 1825) from initial administration, and the median number of cycles was 3 cycles (range 1, 15). Hemolytic anemia was recorded in 64 patients, with a median of 8.3 g/dL (range 4.6, 13). Sixty-three patients had thrombocytopenia with a median of 18 × 109/L (range 1, 139). The median value of increased LDH was 1192 IU/L (range 141, 5378). ADAMTS13 activity was normal in 41 (62.1 %) of the 42 patients. Mutations were found in 9 (13.6 %) of the 15 patients. Fifty-seven patients achieved a clinical response after discontinuing carfilzomib and receiving therapeutic plasma exchange (53.0 %), eculizumab (24.2 %), or hemodialysis (39.4 %).

CONCLUSION

Carfilzomib-induced TMA is an important adverse event that should be considered in patients receiving carfilzomib for multiple myeloma with anemia, thrombocytopenia, and acute kidney injury. Withdrawal of carfilzomib and treatment with eculizumab have proven successful in some patients.

Acute Renal Thrombotic Microangiopathy Caused by Eltrombopag and Romiplostim in a Patient with Myelodysplastic Syndromes (MDS) and Underlying Antiphospholipid Syndrome

Romiplostim and eltrombopag are synthetic agonists of the thrombopoietin receptor (TPO-R), commonly used for immune thrombocytopenic purpura (ITP) and sometimes in myelodysplastic syndrome (MDS). They are rarely associated with kidney injury. We report a case of acute kidney injury caused by romiplostim and eltrombopag in an 80-year-old male patient with MDS and ITP. He did not have systemic haemolysis syndrome but isolated acute renal thrombotic microangiopathy confirmed by kidney biopsy. He was treated with steroids, plasmapheresis and anticoagulation, with improvement in renal function. Interestingly, the patient had high antiphospholipid (aPL) antibodies noted upon screening, indicating a possible new antiphospholipid syndrome (APS) diagnosis. In the presence of circulating aPL antibodies, eltrombopag may have served as a trigger, causing endothelial injury and subsequent renal microangiopathy; aPL antibodies were still significantly positive at four weeks of outpatient testing. This case and a few others reported in the literature highlight the importance of screening for aPL antibodies before initiating TPO-R agonists in patients with ITP. We suspect that using TPO-R agonists, rather than underlying aPL, caused renal failure.

LEARNING POINTS

Synthetic agonists of the thrombopoietin receptor, such as romiplostim or eltrombopag, can cause acute renal failure.Preexisting antiphospholipid (aPL) antibodies may increase the risk of renal failure.Screening for aPL antibodies should be considered before initiating thrombopoietin-receptor agonists (TPO-R agonists) in patients with immune thrombocytopenic purpura (ITP).

Enterohemorrhagic Escherichia coli: trigger for small vessel vasculitis

We describe the case of a 19-year-old woman who presented with abdominal pain, vomiting, and a palpable purpuric rash. The patient subsequently developed dysentery and was found to have an infection from Shiga toxin-producing Escherichia coli. The patient also met diagnostic criteria for IgA vasculitis (also known as Henoch Schönlein purpura) but had negative immunofluorescence biopsies of the rash. The patient was treated with steroids and achieved recovery. To our knowledge, this is the first documented case of IgA vasculitis in the setting of an enterohemorrhagic E. coli infection. This case highlights an atypical presentation of IgA vasculitis and the need to include small vessel vasculitis as a differential diagnosis when treating patients of all ages.

Thrombotic Microangiopathies and the Kidney

Thrombotic microangiopathy (TMA) is a pathological lesion that occurs due to endothelial injury. It can be seen in a heterogenous group of disorders, typically characterized by microangiopathic hemolytic anemia, thrombocytopenia, and end-organ ischemia. TMA can also be renal limited with no systemic manifestations. There are multiple etiologies of a TMA with complement activation being a core underlying mechanism, although the nature and extent of complement involvement can vary. A further complicated factor is the cross talk between complement, neutrophils, and coagulation pathways in the pathophysiology of TMAs. Therefore, a thorough and systematic clinical history and laboratory evaluation are critical to establish the cause and pathophysiology of a TMA. Furthermore, TMAs are associated with significant morbidity and mortality, and timely diagnosis is key for appropriate management and to prevent end-stage kidney disease and other associated complications. In this review, we focus on the pathology, mechanisms, diagnostic work up and treatment of TMAs associated with various etiologies. We also define the complement evaluations that should be conducted in these patients and further highlight the currently approved complement therapies as well as others in the pipeline.

Renal Involvement in Thrombotic Thrombocytopenic Purpura: Is It Time to Challenge the Old Paradigm?

Thrombotic thrombocytopenic purpura (TTP) is clinical-pathological entity characterized by microangiopathic hemolytic anemia associated with end-organ dysfunction. Traditionally, TTP was characterized by the classic pentad of fever, thrombocytopenia, hemolytic anemia, renal impairment, and neurological manifestations. However, this classic pentad is only observed in 40% of cases. We herein describe the case of a female patient who presented with epigastric pain and vomiting and found to have TTP without the classic pentad but with rapidly progressive renal dysfunction.

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.

Investigation of Clinical Features and Association between Vascular Endothelial Injury Markers and Cytomegalovirus Infection Associated with Thrombotic Microangiopathy in Patients with Anti-Neutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis: Case-Based Research

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) can occasionally trigger thrombotic microangiopathy (TMA). Cytomegalovirus (CMV) may be reactivated during intensive immunosuppressive therapy for AAV and cause TMA. Therefore, we aimed to evaluate the clinical features of and the association between vascular endothelial injury markers and TMA due to CMV in patients with AAV. A 61-year-old female was diagnosed with AAV and severe kidney injury. Immunosuppressive therapy gradually improved her symptoms and laboratory findings. However, 2 weeks after induction therapy initiation, she exhibited altered consciousness, a significant decrease in platelet count, and hemolytic anemia, resulting in a TMA diagnosis. Plasma exchange did not improve TMA findings and routine screening test revealed CMV infection. Ganciclovir injection improved the infection and TMA findings. Consequently, we diagnosed her with CMV-induced TMA. Both AAV and CMV may induce severe vascular endothelial injury, potentially leading to TMA development. CMV-induced TMA should be considered when TMA develops during induction therapy against AAV. Moreover, of the three serum markers of vascular injury-serum sulfatides, soluble thrombomodulin, and pentraxin 3-serum sulfatides may be associated with the development of TMA, and a high level of soluble thrombomodulin may be associated with the development of CMV viremia during the clinical course of AAV.

Pregnancy-Induced Thrombotic Microangiopathy in Systematic Lupus Erythematosus: A Case Report

Thrombotic microangiopathy (TMA) is a severe systemic disorder with multiorgan manifestations due to thrombosis of the microvasculature. Pregnancy and post-partum are particularly high-risk periods for many forms of TMA. The disease progression is rapid and can lead to organ failure and even death; therefore, urgent recognition and treatment are paramount. The presence of other triggers such as infections or autoimmune diseases like systematic lupus erythematosus (SLE) can add further complexity, which emphasizes the need for definitive diagnostic investigations such as kidney biopsy to promptly direct further diagnosis and management. We describe a case of a 27-year-old female with post-partum severe acute kidney injury and nephrotic range proteinuria. She had a new diagnosis of active SLE and was found to have TMA on kidney biopsy without conclusive features of lupus nephritis. She was managed successfully with plasma exchange with rapid improvement of her kidney markers.

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

Background

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

Objectives

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

Design

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

Methods

Data in the articles were extracted and analyzed retrospectively.

Results

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

Conclusion

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

A comprehensive model for assessing and classifying patients with thrombotic microangiopathy: the TMA-INSIGHT score

BACKGROUND

Thrombotic Microangiopathy (TMA) is a syndrome characterized by the presence of anemia, thrombocytopenia and organ damage and has multiple etiologies. The primary aim is to develop an algorithm to classify TMA (TMA-INSIGHT score).

METHODS

This was a single-center retrospective cohort study including hospitalized patients with TMA at a single center. We included all consecutive patients diagnosed with TMA between 2012 and 2021. TMA was defined based on the presence of anemia (hemoglobin level < 10 g/dL) and thrombocytopenia (platelet count < 150,000/µL), signs of hemolysis, and organ damage. We classified patients in eight categories: infections; Malignant Hypertension; Transplant; Malignancy; Pregnancy; Thrombotic Thrombocytopenic Purpura (TTP); Shiga toxin-mediated hemolytic uremic syndrome (STEC-SHU) and Complement Mediated TMA (aHUS). We fitted a model to classify patients using clinical characteristics, biochemical exams, and mean arterial pressure at presentation.

RESULTS

We retrospectively retrieved TMA phenotypes using automatic strategies in electronic health records in almost 10 years (n = 2407). Secondary TMA was found in 97.5% of the patients. Primary TMA was found in 2.47% of the patients (TTP and aHUS). The best model was LightGBM with accuracy of 0.979, and multiclass ROC-AUC of 0.966. The predictions had higher accuracy in most TMA classes, although the confidence was lower in aHUS and STEC-HUS cases.

CONCLUSION

Secondary conditions were the most common etiologies of TMA. We retrieved comorbidities, associated conditions, and mean arterial pressure to fit a model to predict TMA and define TMA phenotypic characteristics. This is the first multiclass model to predict TMA including primary and secondary conditions.

Complement and coagulation crosstalk - Factor H in the spotlight

The immune complement and the coagulation systems are blood-based proteolytic cascades that are activated by pathway-specific triggers, based on protein-protein interactions and enzymatic cleavage reactions. Activation of these systems is finely balanced and controlled through specific regulatory mechanisms. The complement and coagulation systems are generally viewed as distinct, but have common evolutionary origins, and several interactions between these homologous systems have been reported. This complement and coagulation crosstalk can affect activation, amplification and regulatory functions in both systems. In this review, we summarize the literature on coagulation factors contributing to complement alternative pathway activation and regulation and highlight molecular interactions of the complement alternative pathway regulator factor H with several coagulation factors. We propose a mechanism where factor H interactions with coagulation factors may contribute to both complement and coagulation activation and regulation within the haemostatic system and fibrin clot microenvironment and introduce the emerging role of factor H as a modulator of coagulation. Finally, we discuss the potential impact of these protein interactions in diseases associated with factor H dysregulation or deficiency as well as evidence of coagulation dysfunction.

Beyond Immunosuppression: The Intricate Relationship Between Tacrolimus and Microangiopathy

Tacrolimus, widely known as Prograf, has become the preferred immunosuppressant for preventing graft rejection in solid organ transplant recipients, particularly in steroid-sparing regimens. Its efficacy and reduced risk of acute and chronic rejection compared to cyclosporine have made it the preferred treatment option for transplant patients. However, tacrolimus has drawbacks as it is associated with adverse effects, such as renal tubular necrosis, kidney failure, hypertension, metabolic acidosis, and new-onset diabetes mellitus. Among the less common but potentially severe complications is thrombotic microangiopathy linked to tacrolimus usage. Identifying and addressing this condition early on is crucial given its severity and potential complications. Manifestations of this microangiopathy can vary, encompassing renal, neurological, cardiac, and respiratory symptoms, and, in some cases, presenting as pancreatitis, intestinal ischemia, or skin abnormalities. Although conventional management often involves plasma exchange as the primary therapeutic option, recent insights into the pathophysiology have led to newer drugs, such as eculizumab and belatacept, offering promising outcomes. In this narrative review, we delve deeper into the underlying pathophysiological mechanisms of tacrolimus-induced thrombotic microangiopathy and aim to provide clinicians with valuable recommendations for efficient and timely treatment strategies. By understanding the complexities of this condition and staying abreast of the latest advancements in therapeutic options, healthcare providers can optimize patient outcomes and ensure safer tacrolimus administration in solid organ transplant recipients.

Complement factor I: Regulatory nexus, driver of immunopathology, and therapeutic

Complement factor I (FI) is the nexus for classical, lectin and alternative pathway complement regulation. FI is an 88 kDa plasma protein that circulates in an inactive configuration until it forms a trimolecular complex with its cofactor and substrate whereupon a structural reorganization allows the catalytic triad to cleave its substrates, C3b and C4b. In keeping with its role as the master complement regulatory enzyme, deficiency has been linked to immunopathology. In the setting of complete FI deficiency, a consumptive C3 deficiency results in recurrent infections with encapsulated microorganisms. Aseptic cerebral inflammation and vasculitic presentations are also less commonly observed. Heterozygous mutations in the factor I gene (CFI) have been demonstrated to be enriched in atypical haemolytic uraemic syndrome, albeit with a very low penetrance. Haploinsufficiency of CFI has also been associated with decreased retinal thickness and is a strong risk factor for the development of age-related macular degeneration. Supplementation of FI using plasma purified or recombinant protein has long been postulated, however, technical difficulties prevented progression into clinical trials. It is only using gene therapy that CFI supplementation has reached the clinic with GT005 in phase I/II clinical trials for geographic atrophy.

Design and Rationale of the APPELHUS Phase 3 Open-Label Study of Factor B Inhibitor Iptacopan for Atypical Hemolytic Uremic Syndrome

Introduction

Atypical hemolytic uremic syndrome (aHUS) is a rare, progressive, and life-threatening form of thrombotic microangiopathy (TMA) which is caused by dysregulation of the alternative complement pathway (AP). Complement inhibition is an effective therapeutic strategy in aHUS, though current therapies require intravenous administration and increase the risk of infection by encapsulated organisms, including meningococcal infection. Further studies are required to define the optimal duration of existing therapies, and to identify new agents that are convenient for long-term administration. Iptacopan (LNP023) is an oral, first-in-class, highly potent, proximal AP inhibitor that specifically binds factor B (FB). In phase 2 studies of IgA nephropathy, paroxysmal nocturnal hemoglobinuria, and C3 glomerulopathy, iptacopan inhibited the AP, showed clinically relevant benefits, and was well tolerated. Iptacopan thus has the potential to become an effective and safe treatment for aHUS, with the convenience of oral administration.

Methods

Alternative Pathway Phase III to Evaluate LNP023 in aHUS (APPELHUS; NCT04889430) is a multicenter, single-arm, open-label, phase 3 study to evaluate the efficacy and safety of iptacopan in patients (N = 50) with primary complement-mediated aHUS naïve to complement inhibitor therapy (including anti-C5). Eligible patients must have evidence of TMA (platelet count <150 × 10⁹/l, lactate dehydrogenase ≥1.5 × upper limit of normal, hemoglobin ≤ lower limit of normal, serum creatinine ≥ upper limit of normal) and will receive iptacopan 200 mg twice daily. The primary objective is to assess the proportion of patients achieving complete TMA response without the use of plasma exchange or infusion or anti-C5 antibody during 26 weeks of iptacopan treatment.

Conclusion

APPELHUS will determine if iptacopan is safe and efficacious in patients with aHUS.

Glucocorticoid-induced thrombotic microangiopathy in paroxysmal nocturnal hemoglobinuria: A case report and review of literature

BACKGROUND

Thrombotic microangiopathy (TMA) is a group of disorders that converge on excessive platelet aggregation in the microvasculature, leading to consumptive thrombocytopenia, microangiopathic hemolysis and ischemic end-organ dysfunction. In predisposed patients, TMA can be triggered by many environmental factors. Glucocorticoids (GCs) can compromise the vascular endothelium. However, GC-associated TMA has rarely been reported, which may be due to the lack of awareness of clinicians. Given the high frequency of thrombocytopenia during GC treatment, particular attention should be given to this potentially fatal complication.

CASE SUMMARY

An elderly Chinese man had a 12-year history of aplastic anemia (AA) and a 3-year history of paroxysmal nocturnal hemoglobinuria (PNH). Three months earlier, methylprednisolone treatment was initiated at 8 mg/d and increased to 20 mg/d to alleviate complement-mediated hemolysis. Following GC treatment, his platelet counts and hemoglobin levels rapidly decreased. After admission to our hospital, the dose of methylprednisolone was increased to 60 mg/d in an attempt to enhance the suppressive effect. However, increasing the GC dose did not alleviate hemolysis, and his cytopenia worsened. Morphological evaluation of the marrow smears revealed increased cellularity with an increased percentage of erythroid progenitors without evident dysplasia. Cluster of differentiation (CD)55 and CD59 expression was significantly decreased on erythrocytes and granulocytes. In the following days, platelet transfusion was required due to severe thrombocytopenia. Observation of platelet transfusion refractoriness indicated that the exacerbated cytopenia may have been caused by the development of TMA due to GC treatment because the transfused platelet concentrates had no defects in glycosylphosphatidylinositol-anchored proteins. We examined blood smears and found a small number of schistocytes, dacryocytes, acanthocytes and target cells. Discontinuation of GC treatment resulted in rapidly increased platelet counts and steady increases in hemoglobin levels. The patient’s platelet counts and hemoglobin levels returned to the levels prior to GC treatment 4 weeks after GC discontinuation.

CONCLUSION

GCs can drive TMA episodes. When thrombocytopenia occurs during GC treatment, TMA should be considered, and GCs should be discontinued.