Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome following allogeneic HPC transplantation: a diagnostic dilemma

Neurological involvement in hematopoietic stem cell transplantation-associated thrombotic microangiopathy

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a well-recognized serious complication of hematopoietic stem cell transplantation (HSCT). The understanding of TA-TMA pathophysiology has expanded in recent years. Dysregulation of the complement system is thought to cause endothelial injury and, consequently, microvascular thrombosis and tissue damage. TA-TMA can affect multiple organs, and each organ exhibits specific features of injury. Central nervous system (CNS) manifestations of TA-TMA include posterior reversible encephalopathy syndrome, seizures, and encephalopathy. The development of neurological dysfunction is associated with a significantly lower overall survival in patients with TA-TMA. However, there are currently no established histopathological or radiological criteria for the diagnosis of CNS TMA. Patients who receive total body irradiation (TBI), calcineurin inhibitors (CNI), and severe acute and chronic graft-versus-host disease (GVHD) are at a high risk of experiencing neurological complications related to TA-TMA and should be considered for directed TA-TMA therapy. However, the incidence and clinical manifestations of TA-TMA neurotoxicity remain unclear. Studies specifically examining the involvement of CNS in TMA syndromes are limited. In this review, we discuss clinical manifestations and imaging abnormalities in patients with nervous system involvement in TA-TMA. We summarize the mechanisms underlying TA-TMA and its neurological complications, including endothelial injury, evidence of complement activation, and treatment options for TA-TMA.

Late transplant-associated thrombotic microangiopathy verified in bone marrow biopsy specimens is associated with chronic GVHD and viral infections

OBJECTIVES

To describe late transplant-associated thrombotic microangiopathy (TA-TMA) as chronic endothelial complication in bone marrow (BM) after allogeneic hematopoietic stem cell transplantation (HSCT).

METHODS

BM specimens along with conventional diagnostic parameters were assessed in 14 single-institutional patients with late TA-TMA (more than 100 days after HCST), including 11 late with history of early TA-TMA, 10 with early TA-TMA (within 100 days), and 12 non TA-TMA patients. Three non-HSCT patients served as control. The time points of BM biopsy were +1086, +798, +396, and +363 days after HSCT, respectively.

RESULTS

Late TA-TMA patients showed an increase of CD34+ and von Willebrand Factor (VWF)+ microvascular endothelial cells with atypical VWF+ conglomerates forming thickened VWF+ plaque sinus in the BM compared to patients without late TA-TMA and non-HSCT. Severe chronic (p = .002), steroid-refractory GVHD (p = .007) and reactivation of HHV6 (p = .002), EBV (p = .003), and adenovirus (p = .005) were pronounced in late TA-TMA. Overall and relapse-free survival were shorter in late TA-TMA than in patients without late TA-TMA (5-year OS and RFS: 78.6% vs. 90.2%, 71.4% vs. 86.4%, respectively).

CONCLUSION

Chronic allo-immune microangiopathy in BM associated with chronic, steroid-refractory GVHD and/or viral infections are key findings of late, high-risk TA-TMA, which deserves clinical attention.

Thrombotic Microangiopathy After Hematopoietic Stem Cell and Solid Organ Transplantation: A Review for Intensive Care Physicians

Intensive care physicians may assume the primary care of patients with transplant-associated thrombotic microangiopathy (TA-TMA), an uncommon but potentially critical complication of hematopoietic stem cell transplants (HSCTs) and solid organ transplants. TA-TMA can have a dramatic presentation with multiple organ dysfunction syndrome (MODS) associated with high morbidity and mortality. The typical presenting clinical features are hemolytic anemia, thrombocytopenia, refractory hypertension, proteinuria and worsening renal failure. Intestinal involvement, with abdominal pain, nausea and vomiting, gastrointestinal bleeding, and ascites are also common. Cardiopulmonary involvement may develop from various causes including pulmonary arteriolar hypertension, pleural and pericardial effusions, and diffuse alveolar hemorrhage. Due to other often concurrent complications after HSCT, early diagnosis and effective management of TA-TMA may be challenging. Close collaboration between ICU and transplant physicians, along with other relevant specialists, is needed to best manage these patients. There are currently no approved therapies for the treatment of TA-TMA. Plasma exchange and rituximab are not recommended unless circulating factor H (CFH) antibodies or thrombotic thrombocytopenic purpura (TTP; ADAMTS activity < 10%) are diagnosed or highly suspected. The role of the complement pathway activation in the pathophysiology of TA-TMA has led to the successful use of targeted complement inhibitors, such as eculizumab. However, the relatively larger studies using eculizumab have been mostly conducted in the pediatric population with limited data on the adult population. This review is focused on the role of intensive care physicians to emphasize the clinical approach to patients with suspected TA-TMA and to discuss diagnosis and treatment strategies.

Prevention and management of acute toxicities from conditioning regimens during hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) remains the only curative option for several hematological malignancies. Its use has continued to grow, with an estimated 23,500 transplants performed annually in the United States alone. The acute toxicities that occur from conditioning chemotherapy can impact the peri-transplant period and have substantial implications on patients' tolerability and outcomes, irrespective of the treatment of their disease. Chemotherapy-induced nausea vomiting (CINV), mucositis, transplant-associated thrombotic microangiopathy (TA-TMA), and sinusoidal obstruction syndrome, also known as a veno-occlusive disease (SOS/VOD) can all have significant implications for patients. These acute complications begin with the start of conditioning chemotherapy and add to potential toxicity for patients throughout the early post-transplant period, from Day +30 for CINV, mucositis, and SOS, and which can continue through at least Day +100 with the onset of TA-TMA. These toxicities must be prevented and managed appropriately. This review will summarize the literature surrounding them and guide their management.

Advances in the ocular complications after hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) has benefited an increasing number of patients with hematological disease in the clinic. It is a curative therapy for malignant and nonmalignant hematological diseases. With the advancement and further clinical application of HSCT in recent years, the life expectancy of patients has increased, but complications have become more common. The occurrence of ocular complications is receiving increasing attention because they can seriously affect the quality of life of patients. Ocular complications require increased attention from clinicians because of their negative impact on patients and increasing incidence. Most of recent reports on posttransplant ocular complications involve ocular manifestations of graft-versus-host disease (GVHD), and a few ocular complications that do not originate from GVHD have also been reported. This review summarizes the diagnosis, scoring criteria, pathophysiology, and clinical manifestations of and common therapies for ocular graft-versus-host disease(oGVHD) after HSCT, and includes a description of some rare cases and novel therapies.

TMA in Kidney Transplantation

Thrombotic microangiopathy (TMA) is a rare and devastating complication of kidney transplantation, which often leads to graft failure. Posttransplant TMA (PT-TMA) may occur either de novo or as a recurrence of the disease. De novo TMA can be triggered by immunosuppressant drugs, antibody-mediated rejection, viral infections, and ischemia/reperfusion injury in patients with no evidence of the disease before transplantation. Recurrent TMA may occur in the kidney grafts of patients with a history of atypical hemolytic uremic syndrome (aHUS) in the native kidneys. Studies have shown that some patients with aHUS carry genetic abnormalities that affect genes that code for complement regulators (CFH, MCP, CFI) and components (C3 and CFB), whereas in 10% of patients (mostly children), anti-FH autoantibodies have been reported. The incidence of aHUS recurrence is determined by the underlying genetic or acquired complement abnormality. Although treatment of the causative agents is usually the first line of treatment for de novo PT-TMA, this approach might be insufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve kidney function. Targeted complement inhibition is an effective treatment for recurrent TMA and may be effective in de novo PT-TMA as well, but it is necessary to establish which patients can benefit from different therapeutic options and when and how these can be applied.

Breaking the graft-versus-host-disease barrier: Mesenchymal stromal/stem cells as precision healers

Mesenchymal Stromal/Stem Cells (MSCs) are multipotent, non-hematopoietic progenitor cells with a wide range of immune modulation and regenerative potential which qualify them as a potential component of cell-based therapy for various autoimmune/chronic inflammatory ailments. Their immunomodulatory properties include the secretion of immunosuppressive cytokines, the ability to suppress T-cell activation and differentiation, and the induction of regulatory T-cells. Considering this and our interest, we here discuss the significance of MSC for the management of Graft-versus-Host-Disease (GvHD), one of the autoimmune manifestations in human. In pre-clinical models, MSCs have been shown to reduce the severity of GvHD symptoms, including skin and gut damage, which are the most common and debilitating manifestations of this disease. While initial clinical studies of MSCs in GvHD cases were promising, the results were variable in randomized studies. So, further studies are warranted to fully understand their potential benefits, safety profile, and optimal dosing regimens. Owing to these inevitable issues, here we discuss various mechanisms, and how MSCs can be employed in managing GvHD, as a cellular therapeutic approach for this disease.

Pulmonary Histopathologic Findings in Pediatric Patients After Hematopoietic Stem Cell Transplantation: An Autopsy Study

BACKGROUND

Pathologic characterization of pulmonary complications following hematopoietic stem cell transplantation (HSCT) is limited. We describe lung findings in pediatric patients who died following HSCT and attempt to identify potential clinical associations.

METHODS

Pathology databases at Texas Children's Hospital and the Children's Hospital of Philadelphia were queried (2013-2018 CHOP and 2017-2018 TCH). Electronic medical records and slides were reviewed.

RESULTS

Among 29 patients, 19 received HSCT for hematologic malignancy, 8 for non-malignant hematologic disorders, and 2 for metastatic solid tumors. Twenty-five patients (86%) showed 1 or more patterns of acute and organizing lung injury. Sixty-two percent had microvascular sclerosis, with venous involvement noted in most cases and not correlating with clinical history of pulmonary hypertension, clinical transplant-associated thrombotic microangiopathy, irradiation, or graft-versus-host disease. Features suggestive of graft-versus-host-disease were uncommon: 6 patients had lymphocytic bronchiolitis, and only 2 patients had evidence of bronchiolitis obliterans (both clinically unexpected), both with a mismatched unrelated donor transplant.

CONCLUSIONS

Acute and subacute alveolar injury (diffuse alveolar damage or organizing pneumonia) is common in pediatric patients who died following HSCT and is difficult to assign to a specific etiology. Microvascular sclerosis was frequent and did not correlate with a single distinct clinical feature.

EASIX score predicts inferior survival after allogeneic hematopoietic cell transplantation

The Endothelial Activation and Stress Index (EASIX) is a prognostic tool that uses common clinical laboratory values and has been shown to predict non-relapse mortality (NRM) and overall survival (OS) at the onset of acute graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). We hypothesized that EASIX calculated at different time points pre- and post- HCT may predict NRM and OS, and that EASIX calculated at onset of GVHD may predict response to steroids. We evaluated the EASIX score pre- and post-HCT in 152 patients with lymphoid malignancies undergoing unmodified reduced intensity conditioning (RIC) alloHCT with uniform GVHD prophylaxis. In multivariate analysis, EASIX calculated pre-HCT was significantly associated with higher NRM (HR = 1.64, p = 0.009) and lower OS (HR = 1.33, p = 0.046). Furthermore, EASIX calculated at day 30 and at day 100 was associated with increased NRM (HR = 1.65, p < 0.001; and HR = 1.65, p < 0.001) and decreased OS (HR = 1.27, p = 0.018; and HR = 1.49, p < 0.001), independent of HCT-CI, disease and conditioning regimen. Our study shows that high EASIX scores at various time points pre- and post-HCT are significantly associated with poorer overall outcomes. EASIX provides an independent and easily accessible tool to predict outcomes that can be complementary to other measures of risk stratification for patients undergoing HCT.

Use of eculizumab in children with allogeneic haematopoietic stem cell transplantation associated thrombotic microangiopathy - a multicentre retrospective PDWP and IEWP EBMT study

Terminal complement blockade by humanised monoclonal antibody eculizumab has been used to treat transplantation-associated thrombotic microangiopathy (TA-TMA) in recent years. This retrospective international study conducted by the Paediatric Diseases (PDWP) and Inborn Error Working Party (IEWP) of the European Society for Blood and Marrow Transplantation (EBMT) describes outcome and response of 82 paediatric patients from 29 centres who developed TA-TMA and were treated with eculizumab between January 2014 and May 2019. The median time from hematopoietic stem cell transplantation (HSCT) to TA-TMA manifestation was 92 days (range: 7-606) and from TA-TMA diagnosis to the start of eculizumab treatment 6 days (range: 0-135). Most patients received eculizumab weekly (72%, n = 55) with a standard weight (kg)-based dose (78%, n = 64). Six months from beginning of eculizumab therapy, the cumulative incidence of TA-TMA resolution was 36.6% (95% CI: 26.2-47) and the overall survival (OS) was 47.1% (95% CI: 35.9-57.5). All 43 patients with unresolved TA-TMA died. The cause of death was HSCT-related in 41 patients. This study also documents poor outcome of patients without aGvHD and their frequent concomitant viral infections. Considering recent publications, intensified eculizumab dosing and complement monitoring could potentially improve upon outcomes observed in this study.

Epidemiology and outcomes of pediatric transplant-associated thrombotic microangiopathy in Hong Kong

BACKGROUND

Transplant-associated thrombotic microangiopathy (TA-TMA) is an under-recognized yet potentially devastating complication of hematopoietic stem cell transplantation (HSCT) which had increased awareness in recent years. This report summarizes the demographics and outcomes of pediatric TA-TMA in Hong Kong.

METHODS

All patients aged below 18 years who underwent HSCT in the Hong Kong Children's Hospital and were diagnosed to have TA-TMA during the 2-year period from April 1, 2019 to March 31, 2021 were included.

RESULTS

A total of 73 transplants (51 allogeneic and 22 autologous) in 63 patients had been performed. Six patients (four males and two females) developed TA-TMA at a median duration of 2.5 months post-HSCT. The incidence rate was 9.52%. Of the six TA-TMA patients, five underwent allogenic one underwent autologous HSCT, respectively. Three of them were histologically proven. All four patients with cyclosporine had stopped the drug once TA-TMA was suspected. Median six doses of eculizumab were administered to five out of six patients. Three patients died (two due to fungal infection and one due to acute-on-chronic renal failure) within 3 months upon diagnosis of TA-TMA. Among three survivors, two stabilized with mild stage 2 chronic kidney disease (CKD) while the other suffered from stage 5 end-stage CKD requiring lifelong dialysis.

CONCLUSION

In conclusion, recognition and diagnosis of TA-TMA are challenging. Early recognition and prompt administration of complement blockage with eculizumab may be beneficial in selected cases. Further prospective research studies are recommended to improve the management and outcomes of TA-TMA.

N-Acetylcysteine as Prophylactic Therapy for Transplantation-Associated Thrombotic Microangiopathy: A Randomized, Placebo-Controlled Trial

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a life-threatening complication for patients undergoing hematopoietic stem cell transplantation (HSCT). N-acetylcysteine (NAC) has recently been considered as a potential treatment for patients with thrombotic thrombocytopenic purpura. To assess the value of NAC for the prevention of TA-TMA, we conducted a prospective study at the First Affiliated Hospital of Soochow University. This open-label, randomized placebo-controlled trial included 160 patients who were scheduled for allogeneic HSCT. Participants were assigned at random 1:1 to either oral NAC (50 mg/kg/day from 9 days before HSCT to 30 days after HSCT) or placebo treatment. The primary outcome was the incidence of TA-TMA. Overall survival (OS) and event-free survival (EFS) were assessed in the NAC and placebo control groups. The incidence of TA-TMA was 9.1% (95% confidence interval [CI], 2% to 16.2%) in the NAC group, compared with 23% (95% CI, 13.2% to 32.8%) in the control group, with a rate ratio of .34 (95% CI, .123 to .911; P = .039). The median time to the onset of TA-TMA was 60 days (interquartile range [IQR], 42 to 129 days) in the NAC group and 36 days (IQR, 30.5 to 51 days) in the control group (P = .063). The 2-year OS rate was 75.4% (95% CI, 28.65% to 73.53%) in the NAC group and 63.0% (95% CI, 50.8% to 73.5%) in the control group, with a hazard ratio (HR) of .622 (95% CI, .334-1.155; P = .132). The EFS rate was 25.8% in the NAC patients and 8.1% in controls (HR, .254; 95% CI, .094 to .692; P = .024). The median time of EFS was 60 days in the NAC group and 38 days in controls. Our findings suggest that NAC may be a potential treatment to reduce the incidence of TA-TMA.

Complement System as a New Target for Hematopoietic Stem Cell Transplantation-Related Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a complication that may occur after autologous or allogeneic hematopoietic stem cell transplantation (HSCT) and is conventionally called transplant-associated thrombotic microangiopathy (TA-TMA). Despite the many efforts made to understand the mechanisms of TA-TMA, its pathogenesis is largely unknown, its diagnosis is challenging and the case-fatality rate remains high. The hallmarks of TA-TMA, as for any TMA, are platelet consumption, hemolysis, and organ dysfunction, particularly the kidney, leading also to hypertension. However, coexisting complications, such as infections and/or immune-mediated injury and/or drug toxicity, together with the heterogeneity of diagnostic criteria, render the diagnosis difficult. During the last 10 years, evidence has been provided on the involvement of the complement system in the pathophysiology of TA-TMA, supported by functional, genetic, and therapeutic data. Complement dysregulation is believed to collaborate with other proinflammatory and procoagulant factors to cause endothelial injury and consequent microvascular thrombosis and tissue damage. However, data on complement activation in TA-TMA are not sufficient to support a systematic use of complement inhibition therapy in all patients. Thus, it seems reasonable to propose complement inhibition therapy only to those patients exhibiting a clear complement activation according to the available biomarkers. Several agents are now available to inhibit complement activity: two drugs have been successfully used in TA-TMA, particularly in pediatric cases (eculizumab and narsoplimab) and others are at different stages of development (ravulizumab, coversin, pegcetacoplan, crovalimab, avacopan, iptacopan, danicopan, BCX9930, and AMY-101).

Unique Presentation of Bortezomib-Associated Thrombotic Microangiopathy Responsive to Therapeutic Plasma Exchange and Eculizumab Therapy

Thrombotic microangiopathies (TMA) are a rare group of life-threatening hematological conditions characterized by thrombocytopenia and microangiopathic hemolytic anemia. Although our understanding of the pathophysiology and the availability of diagnostic testing has improved for primary TMAs, such as thrombotic thrombocytopenic purpura, the pathophysiology underlying secondary TMAs, including drug-induced TMAs (DITMAs), remains less clear. In this case report, we present the unique case of a patient with a history of multiple myeloma that presented four months after the initiation of bortezomib therapy with a bortezomib-associated TMA that responded to therapeutic plasma exchange (TPE) with plasma replacement and eculizumab therapy. This case demonstrates the possible utility of TPE with plasma replacement and eculizumab therapy in DITMA patients that fail to respond following a trial of holding the suspected medication.

Acute graft-versus-host disease increase risk and accuracy in prediction model of transplantation-associated thrombotic microangiopathy in patients with myelodysplastic syndrome

Allogeneic hematopoietic stem cell transplantation is the only curative therapy for patients with myelodysplastic syndrome. Transplantation-associated thrombotic microangiopathy (TA-TMA) remains a cause of death after transplantation. This study assessed the risk factors of TA-TMA and established a prediction model for this complication. We launched a real-world study from 303 MDS patients after allo-HSCT from Dec 1, 2007, to Jun 1, 2018. Logistic regression was used to analyze risk factors and to establish a nomogram. The accuracy of the model was assessed by C-index and calibration curve. TA-TMA class was associated with an over twofold increase in the risk of death (HR 2.66, 95% CI 1.39-5.09, p = 0.003). Stage III or IV acute graft-versus-host disease (aGVHD) (OR: 6.17, 95% CI: 2.19-17.18, p < 0.001) and occurrence time of aGVHD were the risk factors for TA-TMA. Next, we put these two variants and the other three variants into the prediction model via multivariate Lasso regression. In order to quantify the contribution of each factor, a nomogram was generated and displayed (C index of 0.783). TA-TMA predicts worsened outcomes of overall survival. A cross-validated multivariate score including aGVHD occurrence showed excellent concordance and efficacy of predicting TA-TMA in HSCT patients.

Incidence and risk factors of transplant-associated thrombotic microangiopathy (TA-TMA): a systematic review and meta-analysis

BACKGROUND

Transplant-associated thrombotic microangiopathy (TA-TMA) is an increasingly recognized post-transplant complication, yet the overall incidence of the disease remains debated.

OBJECTIVES

To determine the pooled incidence of TA-TMA in a systematic review of literature and to identify consistent risk factors.

STUDY DESIGN

We performed a systematic review using Medline, Embase, and CENTRAL databases to identify cohort studies that reported incidence of and risk factors for TA-TMA from 2004 to 2020. We conducted a meta-analysis of proportion to estimate the pooled incidence of TA-TMA using a random-effects model. We assessed moderators of heterogeneity through subgroup analysis, risk of bias through ROBINS-I, and publication bias through funnel plot.

RESULTS

Among 21 cohort studies with 36,163 adult and pediatric patients that underwent allogeneic transplant, the pooled incidence of TA-TMA was 12% (95% CI 9-16). The diagnostic criteria used to define the disease was the most significant contributor identified to the high inter-study heterogeneity (I² 98%). Studies using provider/clinician diagnosis instead of laboratory diagnosis reported the lowest incidence at 3%. The most salient risk factor for TA-TMA reported in 14 studies was preceding acute graft-versus-host disease (GVHD). Other risk predictors described in 5 or more studies included preceding infection, prior transplant, mismatched donor, and myeloablative conditioning.

CONCLUSION

With a pooled incidence at 12% among a significantly heterogeneous population, TA-TMA is an important but relatively uncommon post-transplant complication. Given the divergence between laboratory-based and provider-based incidence, as well as the multitude of risk factors beyond acute GVHD, future studies should focus on risk stratifying the subset of TA-TMA patients who would benefit from therapeutic intervention.

Haploidentical hematopoietic stem cell transplantation for pediatric patients with chronic active Epstein-Barr virus infection: a retrospective analysis of a single center

BACKGROUND

This study aimed to evaluate the feasibility and clinical effect of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for the treatment of pediatric patients with chronic active Epstein-Barr virus infection (CAEBV).

METHODS

Children with CAEBV who did not have matched donors and underwent haplo-HSCT in Beijing Children's Hospital, Capital Medical University, from October 2016 to June 2020 were analyzed retrospectively. Data relating to the clinical manifestations, engraftment, and prognosis of the children were extracted from medical records.

RESULTS

Twenty-five patients, including 16 males and 9 females, with an onset age of 5.0 ± 2.6 years and a transplantation age of 6.9 ± 2.9 years, were enrolled in this study. The mean time from diagnosis to transplantation was 3.8 (2.0-40.2) months. The mean observation time was 19.0 ± 12.0 months. Three patients received the reduced intensity conditioning regimen, and the remaining patients all received the modified myeloablative conditioning regimen. By the end of the follow-up, 23 patients were characterized by disease-free survival (DFS), 22 were characterized by event-free survival (EFS), and two died. One of the patients died of thrombotic microangiopathy (TMA), and another died of graft versus host disease (GVHD); this patient discontinued the treatment for economic reasons. The 3-year overall survival (OS) rate was estimated to be 92.0% ± 5.4%, and the 3-year EFS rate was estimated to be 87.4% ± 6.8%. All active patients survived after HSCT event-free. Acute GVHD degrees 1-3 were observed in ten patients (40.0%), and degree IV was observed in six (24.0%), who were all cured except for one patient. Chronic GVHD was observed in nine (36.0%), and most of these cases were mild. The incidence of TMA and veno-occlusive disease (VOD) was 28.0% and 4.0%.

CONCLUSIONS

Haploidentical hematopoietic stem cell transplantation is safe and effective in the treatment of pediatric CAEBV and can be used as an alternative therapy without matched donors or emergency transplantation. Patients with active disease before HSCT also benefited from haplo-HSCT. Haplo-HSCT requires careful monitoring for complications, such as GVHD and TMA. Early detection of TMA and timely treatment can reduce mortality and can improve the survival rate.

Management of thrombotic microangiopathy after hematopoietic cell transplantation: A position statement of ThREG (Turkish Hematology Research and Education Group)

Hematopoietic stem cell transplantation associated-thrombotic microangiopathy (TA-HCT) is one of the early complications of endothelial origin in the course of HCT. Endothelial damage to the microvascular structure and the platelet-rich microthrombi, which are formed as a result of accompanying complement activation, constitute the main pathological conditions resulting TA-TMA. Early diagnosis and management are of utmost importance to prevent multi-organ failure and death. This review summarizes the current understanding of TA-TMA regarding pathogenesis, definition, differential diagnosis, risk factors, surveillance for early diagnosis and management.

Two Cases of Tacrolimus-related Transplant-associated Thrombotic Microangiopathy Retinopathy after Allogenic Peripheral Blood Stem Cell Transplantation

Purpose: We report two cases of tacrolimus-related transplant-associated thrombotic microangiopathy (TA-TMA) retinopathy in leukemia patients who had undergone allogenic peripheral blood stem cell transplantation (PBSCT).Case summary: (Case 1) A 58-year-old woman with a history of PBSCT due to acute myelocytic leukemia and taking tacrolimus was referred to the ophthalmology clinic with visual disturbance. Her visual acuity (VA) was 0.4 in the right eye and 0.5 in the left eye. Multiple cotton wool spots and retinal hemorrhages were found in both eyes on fundus examination. Multiple capillary non-perfusions were seen on fluorescein angiography (FA). Tacrolimus-related TA-TMA retinopathy was suspected. Tacrolimus was discontinued and plasmapheresis was performed. After 3 months, neovascular glaucoma developed and her VA became “counting fingers” at 20 cm in both eyes. (Case 2) A 20-year-old man with a history of PBSCT due to acute lymphocytic leukemia and taking tacrolimus was referred to our clinic because of decreased VA in both eyes. His VA was 0.05 in the right eye and 0.025 in the left eye. Fundus and FA findings were the same as in Case 1, and the patient was suspected to have tacrolimus-related TA-TMA retinopathy. Tacrolimus was discontinued and plasmapheresis was performed. His VA was 0.2 in the right eye and 0.4 in the left eye at 1 month after treatment.Conclusions: It is necessary to consider TA-TMA retinopathy in leukemia patients taking calcineurin inhibitors, such as tacrolimus, who have decreased VA. Early diagnosis and treatment are important.

Infection in Patients with Suspected Thrombotic Microangiopathy Based on Clinical Presentation

BACKGROUND AND OBJECTIVES

In contrast to shigatoxin-associated Escherichia coli (STEC) causing hemolytic uremic syndrome, STEC-unrelated infections associated with thrombotic microangiopathy are less characterized.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our retrospective study in a four-hospital institution of 530 consecutive patients with adjudicated thrombotic microangiopathies during the 2009-2016 period studied STEC-unrelated infections' epidemiology and major outcomes (death, acute dialysis, and major cardiovascular events).

RESULTS

STEC-unrelated infection was present in 145 of 530 (27%) patients, thrombotic microangiopathies without infection were present in 350 of 530 (66%) patients, and STEC causing hemolytic and uremic syndrome was present in 35 of 530 (7%) patients. They (versus thrombotic microangiopathy without infection) were associated with age >60 years (36% versus 18%), men (53% versus 27%), altered consciousness (32% versus 11%), mean BP <65 mm Hg (21% versus 4%), lower hemoglobin and platelet count, and AKI (72% versus 49%). They were associated with more than one pathogen in 36 of 145 (25%) patients (either isolated [14%] or combined [86%] to other causes of thrombotic microangiopathy); however, no significant clinical or biologic differences were noted between the two groups. They were more frequently due to bacteria (enterobacteria [41%], Staphylococcus aureus [11%], and Streptococcus pneumonia [3%]) than viruses (Epstein-Barr [20%], cytomegalovirus [18%], influenza [3%], hepatitis C [1%], HIV [1%], and rotavirus [1%]). STEC-unrelated infections were independent risk factors for in-hospital death (odds ratio, 2.22; 95% confidence interval, 1.18 to 4.29), major cardiovascular event (odds ratio, 3.43; 95% confidence interval, 1.82 to 6.69), and acute dialysis (odds ratio, 3.48; 95% confidence interval, 1.78 to 7.03). Bacteria (versus other pathogens), and among bacteria, enterobacteria, presence of more than one bacteria, and E. coli without shigatoxin were risk factors for acute dialysis.

CONCLUSIONS

Infections are frequent thrombotic microangiopathy triggers or causes, and they are mostly unrelated to STEC. Infections convey a higher risk of death and major complications. The most frequent pathogens were enterobacteria, S. aureus, Epstein-Barr virus, and cytomegalovirus.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_09_07_CJN17511120.mp3.

A prognostic model (BATAP) with external validation for patients with transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is a potentially life-threatening complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Information on markers for early prognostication remains limited, and no predictive tools for TA-TMA are available. We attempt to develop and validate a prognostic model for TA-TMA. A total of 507 patients who developed TA-TMA following allo-HSCT were retrospectively identified and separated into a derivation cohort and a validation cohort according to the time of transplantation to perform external temporal validation. Patient age (OR 2.371, 95% CI 1.264-4.445), anemia (OR 2.836, 95% CI 1.566-5.138), severe thrombocytopenia (OR 3.871, 95% CI 2.156-6.950), elevated total bilirubin (OR 2.716, 95% CI 1.489-4.955) and proteinuria (OR 2.289, 95% CI 1.257-4.168) were identified as independent prognostic factors for the 6-month outcome of TA-TMA. A risk score model termed BATAP (Bilirubin, Age, Thrombocytopenia, Anemia, Proteinuria) was then constructed according to the regression coefficients. The validated c-statistics were 0.816 (95% CI 0.766-0.867) and 0.756 (95% CI 0.696-0.817) in the internal and external validation, respectively. Calibration plots indicated that the model-predicted probabilities correlated well with the actual observed frequencies. This predictive model may facilitate the prognostication of TA-TMA and contribute to the early identification of high-risk patients.

Risk factors for transplant-associated thrombotic microangiopathy and mortality in a pediatric cohort

Transplant-associated thrombotic microangiopathy (TA-TMA) is a well-recognized complication of hematopoietic cell transplantation (HCT). Diagnosis is challenging and in the absence of a tissue biopsy, TA-TMA is provisionally diagnosed by meeting clinical criteria. In this study, we describe the prevalence, outcomes, and risk factors for meeting 2 different diagnostic criteria for TA-TMA and for increased transplant-related mortality (TRM). In this retrospective study of 307 pediatric HCT patients, records were reviewed for the first 100 days after HCT. Patients who were diagnosed with TA-TMA by a provider during this time were included. In addition, the Cho et al criteria (2010) and Jodele et al (2014) TA-TMA criteria were applied retrospectively. Eight patients (2.6%) were diagnosed with TA-TMA by their provider. However, on retrospective review, 20% and 36% met the Cho and Jodele criteria for TA-TMA, respectively. Overall survival was significantly worse (P < .0001) and TRM was significantly higher in patients who met criteria for TA-TMA (MC-TA-TMA) (P < .0001). After controlling for comorbid conditions, MC-TA-TMA (hazard ratio [HR], 10.9; P = .0001) and grade 3/4 acute graft-versus-host-disease (aGVHD) (HR 3.5; P = .01) remained independently associated with increased TRM. Among allogeneic HCT recipients, features associated with an increased risk for MC-TA-TMA included ≥2 HCT, concurrent grade 3/4 aGVHD and concurrent infections. Among patients who MC-TA-TMA, LDH ≥2 times the upper limit of normal (P = .001), the need for ≥2 antihypertensive medications (P < .0001), and acute kidney injury (P = .003) were associated with significantly increased TRM.

Thrombotic microangiopathy in oncology - a review

Thrombotic microangiopathy is a syndrome triggered by a wide spectrum of situations, some of which are specific to the Oncology setting. It is characterized by a Coombs-negative microangiopathic haemolytic anemia, thrombocytopenia and organ injury, with characteristic pathological features, resulting from platelet microvascular occlusion.

TMA is rare and its cancer-related subset even more so. TMA triggered by drugs is the most common within this group, including classic chemotherapy and the latest targeted therapies. The neoplastic disease itself and hematopoietic stem-cell transplantation could also be potential triggers.

Evidence-based medical guidance in the management of cancer-related TMA is scarce and the previous knowledge about primary TMA is valuable to understand the disease mechanisms and the potential treatments.

Given the wide spectrum of potential causes for TMA in cancer patients, the aim of this review is to gather the vast information available. For each entity, pathophysiology, clinical features, therapeutic approaches and prognosis will be covered.

Microvascular thrombosis: experimental and clinical implications

A significant amount of clinical and research interest in thrombosis is focused on large vessels (eg, stroke, myocardial infarction, deep venous thrombosis, etc.); however, thrombosis is often present in the microcirculation in a variety of significant human diseases, such as disseminated intravascular coagulation, thrombotic microangiopathy, sickle cell disease, and others. Further, microvascular thrombosis has recently been demonstrated in patients with COVID-19, and has been proposed to mediate the pathogenesis of organ injury in this disease. In many of these conditions, microvascular thrombosis is accompanied by inflammation, an association referred to as thromboinflammation. In this review, we discuss endogenous regulatory mechanisms that prevent thrombosis in the microcirculation, experimental approaches to induce microvascular thrombi, and clinical conditions associated with microvascular thrombosis. A greater understanding of the links between inflammation and thrombosis in the microcirculation is anticipated to provide optimal therapeutic targets for patients with diseases accompanied by microvascular thrombosis.

Thrombotic Microangiopathy after Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis

Transplant-associated thrombotic microangiopathy (taTMA) is a systemic vascular illness associated with significant morbidity and mortality, resulting from a convergence of risk factors after allogeneic blood or marrow transplantation (alloBMT). The diagnosis of taTMA has been a challenge, but most criteria include an elevated lactate dehydrogenase (LDH), low haptoglobin, and schistocytes on peripheral blood smear. We performed a retrospective review of the 678 consecutive adults who received high-dose post-transplantation cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis between January 1, 2015, and August 31, 2018. In April 2016, we initiated a monitoring program of weekly LDH and haptoglobin measurements and blood smears when those 2 parameters were both abnormal on all of our adult patients undergoing alloBMT for hematologic malignancies. During the entire period, the 1-year cumulative incidence of taTMA was 1.4% (95% confidence interval, 0.5% to 2.3%). Eight patients were taking tacrolimus at the time of diagnosis, and 1 was not on any immunosuppression. Eight of 9 patients (89%) were hypertensive. Four patients had invasive infections at the time of diagnosis, 4 patients required renal replacement therapy, and 5 of 9 patients were neurologically impaired. Eculizumab was given to 6 patients (0.9%), of whom 2 died and 4 recovered with resolution of end-organ dysfunction. The paucity of events made the determination of risk factors difficult; however, the low incidence of taTMA in this cohort may be related to the limited use of myeloablative conditioning regimens, low incidence of severe GVHD, and use of PTCy. PTCy-based GVHD prophylaxis appears to be associated with a low incidence of severe taTMA.

New insights into risk factors for transplant-associated thrombotic microangiopathy in pediatric HSCT

This study aimed to identify a risk profile for development of transplant-associated thrombotic microangiopathy (TA-TMA) in children undergoing hematopoietic stem cell transplantation (HSCT). Between 2013 and 2016, 439 children underwent 474 HSCTs at 2 supraregional United Kingdom centers. At a median of 153 days post-HSCT, TA-TMA occurred among 25 of 441 evaluable cases (5.6%) with no evidence of center variation. Sex, underlying disease, intensity of the conditioning, total body irradiation-based conditioning, the use of calcineurin inhibitors, venoocclusive disease, and viral reactivation did not influence the development of TA-TMA. Donor type: matched sibling donor/matched family donor vs matched unrelated donor vs mismatched unrelated donor/haplo-HSCT, showed a trend toward the development of TA-TMA in 1.8% vs 6.1% vs 8.3%, respectively. Presence of active comorbidity was associated with an increased risk for TA-TMA; 13% vs 3.7% in the absence of comorbidity. The risk of TA-TMA was threefold higher among patients who received >1 transplant. TA-TMA rates were significantly higher among patients with acute graft-versus-host disease (aGVHD) grades III to IV vs aGVHD grade 0 to II. On multivariate analysis, the presence of active comorbidity, >1 transplant, aGVHD grade III to IV were risk factors for TA-TMA (odds ratio [OR]: 5.1, 5.2, and 26.9; respectively), whereas the use of cyclosporine A/tacrolimus-based GVHD prophylaxis was not a risk factor for TA-TMA (OR: 0.3). Active comorbidity, subsequent transplant, and aGVHD grades III to IV were significant risk factors for TA-TMA. TA-TMA might represent a form of a vascular GVHD, and therefore, continuing control of aGVHD is important to prevent worsening of TA-TMA associated with GVHD.

The induction strategies administered in the treatment of multiple myeloma exhibit a deleterious effect on the endothelium

Multiple myeloma induction treatment includes proteasome inhibitors (PI) and immunomodulatory agents at present. The incidence of engraftment syndrome, a transplant complication potentially related to endothelium, has increased in the last years. Our aim was to investigate whether bortezomib (Velcade, V), thalidomide (T), and dexamethasone (D) affect the endothelium, and explore defibrotide (DF) as protective agent. Endothelial cells (ECs) in culture were exposed to the compounds separately or in combination, without (VTD) and with DF (VTD + DF). Changes in markers of: (i) inflammation (ICAM-1 expression and leukocyte adhesion), (ii) VWF production, (iii) cell permeability (VE-cadherin expression and cell monolayer integrity), and (iv) oxidative stress (ROS production and eNOS expression) were measured. ICAM-1 and VWF expression increased significantly in VTD but were similar to controls in VTD + DF. Separately, bortezomib was the main deleterious agent whereas dexamethasone showed no harmful effect. Leukocyte adhesion showed similar trends. VE-cadherin expression was lower in VTD and normalized in VTD + DF. EC permeability increased only with bortezomib. No changes were observed in oxidative stress markers. Our results demonstrate that bortezomib damages the endothelium, and DF prevents this effect. A better knowledge of the induction drugs impact will allow the design of measures to protect the endothelium.

A Fatal Case of Thrombotic Microangiopathy Without Schistocytosis and Absent Biochemical Markers of Hemolysis

Thrombotic microangiopathy (TMA) is characterized by microangiopathic hemolytic anemia with thrombocytopenia. In addition to the primary TMA syndromes, microangiopathic hemolytic anemia with thrombocytopenia can be seen in many systemic diseases. Transplant associated TMA (TA-TMA) affects patients following stem cell or solid organ transplant. A 48-year-old male who underwent autologous stem cell transplant for nonsecretory multiple myeloma was admitted to our hospital with worsening anemia, thrombocytopenia, renal dysfunction and hepatosplenomegaly. Initial blood work revealed rare schistocytes and normal lactate dehydrogenase and haptoglobin levels. He underwent an extensive workup looking for an infectious, inflammatory or malignant etiology but a definitive diagnosis could not be reached. Over his prolonged stay at the hospital, he suffered from multiorgan failure and eventually passed away. An autopsy revealed TMA involving all clinically affected organ systems and was deemed to be the cause of his demise. The absence of typical blood work suggestive of hemolysis does not rule out a diagnosis of TA-TMA. Knowledge of this rare disease entity will help physicians identify and treat this life-threatening condition early and effectively.

Incidence, Risk Factors for and Outcomes of Transplant-Associated Thrombotic Microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is a complication of allogeneic transplantation (allo-HCT). The incidence and risk factors associated with TA-TMA are not well known. A retrospective analysis from the Center for International Blood and Marrow Transplant Research (CIBMTR) was conducted including patients receiving allo-HCT between 2008 and 2016, with the primary objective of evaluating the incidence of TA-TMA. Secondary objectives included identification of risk factors associated with TA-TMA, and the impact of TA-TMA on overall survival and the need for renal replacement therapy (RRT). Among 23,665 allo-HCT recipients, the 3-year cumulative incidence of TA-TMA was 3%. Variables independently-associated with increased incidence of TA-TMA included female sex, prior autologous transplant, primary disease (acute lymphoblastic leukaemia and severe aplastic anaemia), donor type (mismatched or unrelated donor), conditioning intensity (myeloablative), GVHD prophylaxis (sirolimus + calcineurin inhibitor), pre-transplant kidney dysfunction and acute GVHD (time-varying effect). TA-TMA was associated with higher mortality (HR = 3·1, 95% Confidence Interval [CI] = 2·8-16·3) and RRT requirement (HR = 7·1, 95% CI = 5·7-311·6). This study provides epidemiologic data on TA-TMA and its impact on transplant outcomes. Increased awareness of the risk factors will enable providers to be vigilant of this uncommon but serious transplant complication. The results will also provide benchmarking for future study designs and comparisons.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

Distribution of Transplantation-Associated Thrombotic Microangiopathy (TA-TMA) and Comparison between Renal TA-TMA and Intestinal TA-TMA: Autopsy Study

Transplantation-associated thrombotic microangiopathy (TA-TMA) is an important complication of hematopoietic stem cell transplantation. To date, information regarding the organs that are affected by TA-TMA as confirmed histologically remains limited; the clinicopathologic differences between renal TA-TMA and intestinal TA-TMA have not been examined despite being the well-known and commonly affected sites of TA-TMA. We therefore examined 165 autopsied patients after hematopoietic stem cell transplantation and compared the clinicopathologic factors of renal and intestinal TA-TMA. It was clear that 38 (23%) of our patients had TA-TMA. In the TA-TMA cases, the kidney (61%) and intestine (53%) were commonly affected, and the ileum and right colon were vulnerable. Other organs that we found to be affected by TA-TMA included the stomach (8%), gallbladder (5%), and oral cavity, pharynx, esophagus, liver, heart, urinary bladder, and ureter (all at 3%), and symptoms thought to be caused by TA-TMA of these organs were not observed in any patient. Histologically, TA-TMA only affected the arteriole, or small arteries, regardless of the organ, and the veins or larger arteries were not affected at all. In the kidney, the glomerular capillary was also affected, and mesangiolysis and double contours of the basement membranes were often in evidence. The histologic overlap of renal and intestinal TA-TMA was rare (13%), and the patients in the intestinal TA-TMA group exhibited more frequency of a history of intestinal acute graft-versus-host disease (GVHD) during the clinical course compared with that of the renal TA-TMA group (80% versus 22%, P = .0016). Although TA-TMA can affect many other organs, the frequency of these ancillary events was low, and the clinical effect may have been small. Our results suggest that in comparison to renal TA-TMA, intestinal GVHD could be more closely associated with intestinal TA-TMA as a risk factor.

Severe, persistent neurotoxicity after transplant-associated thrombotic microangiopathy in a pediatric patient despite treatment with eculizumab

BACKGROUND

TA-TMA is a described complication of aHCT in children with neuroblastoma. Outcomes are poor with mortality rates approaching 60%. Described late effects in survivors include chronic kidney disease and persistent pulmonary hypertension.

CASE

We report a case of a 2-year-old with neuroblastoma who developed severe TA-TMA 35 days after high dose chemotherapy and autologous stem cell rescue. He presented with respiratory failure, pericardial and pleural effusions, hemolysis, hypertension, and mild altered mental status. He was mechanically ventilated for 3 weeks and after sedation was lifted, he was minimally responsive. He was treated with eculizumab with resolution of hemolysis, kidney injury and polyserositis. Initially he was more responsive; however, after almost a year of intensive therapy he remained nonverbal and had persistent irritability and behavioral changes. He had an extensive negative evaluation. On day +345, he presented with severe, refractory epilepsy. Three years after TA-TMA, he continues to have severe neurologic disabilities.

CONCLUSIONS

To our knowledge, persistent neurologic toxicity has not been reported in TA-TMA. However, deficits and seizures are reported in other TMAs, particularly in children with atypical HUS who present with significant neurologic changes at diagnosis. Our patient's persistent neurologic disability despite eculizumab response in all other involved organs may reflect irreversible damage. This case describes a new long-term sequela of TA-TMA and highlights the need for further studies to understand both acute and long-term neurologic complications of this disease.

Purtscher-like retinopathy: A rare presentation of hematopoietic stem cell transplant-associated thrombotic microangiopathy

Hematopoietic stem cell transplant (HSCT)-associated (TA) thrombotic microangiopathy (TMA) is an acquired disorder and a potentially life-threatening complication after allogeneic HSCT. TA-TMA causes endothelial damage and results in micro-thrombi in capillaries and arterioles. Early detection and treatment of complications associated with TA-TMA might improve outcomes. Purtscher-like retinopathy (PLR) is associated with micro-thrombi that occlude the retinal arteries and cause retinal injury. PLR has been associated with multiple entities, including HUS and TTP, but has not previously been described in the setting of TA-TMA. Here, we describe an 18-year-old male who underwent a mismatched unrelated donor HSCT for relapsed acute lymphoblastic leukemia. The patient was diagnosed with TA-TMA based on standard defined criteria. He presented with acute onset of blurred vision with findings of multiple white retinal patches, retinal hemorrhages, and macular edema, thought initially to be hypertensive retinopathy. However, on further evaluation using fluorescein angiography and optical coherence tomography, the diagnosis was determined to be PLR. The patient was treated with intravitreal steroid injections (triamcinolone acetonide) with dramatic improvement of vision. The aim of this report is to make clinicians aware of PLR as a potential ocular complication associated with TA-TMA and that prompt intervention might reverse visual impairment.

Complement in Thrombotic Microangiopathies: Unraveling Ariadne's Thread Into the Labyrinth of Complement Therapeutics

Thrombotic microangiopathies (TMAs) are a heterogeneous group of syndromes presenting with a distinct clinical triad: microangiopathic hemolytic anemia, thrombocytopenia, and organ damage. We currently recognize two major entities with distinct pathophysiology: thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Beyond them, differential diagnosis also includes TMAs associated with underlying conditions, such as drugs, malignancy, infections, scleroderma-associated renal crisis, systemic lupus erythematosus (SLE), malignant hypertension, transplantation, HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets), and disseminated intravascular coagulation (DIC). Since clinical presentation alone is not sufficient to differentiate between these entities, robust pathophysiological features need to be used for early diagnosis and appropriate treatment. Over the last decades, our understanding of the complement system has evolved rapidly leading to the characterization of diseases which are fueled by complement dysregulation. Among TMAs, complement-mediated HUS (CM-HUS) has long served as a disease model, in which mutations of complement-related genes represent the first hit of the disease and complement inhibition is an effective and safe strategy. Based on this knowledge, clinical conditions resembling CM-HUS in terms of phenotype and genotype have been recognized. As a result, the role of complement in TMAs is rapidly expanding in recent years based on genetic and functional studies. Herein we provide an updated overview of key pathophysiological processes underpinning complement activation and dysregulation in TMAs. We also discuss emerging clinical challenges in streamlining diagnostic algorithms and stratifying TMA patients that could benefit more from complement modulation. With the advent of next-generation complement therapeutics and suitable disease models, these translational perspectives could guide a more comprehensive, disease- and target-tailored complement intervention in these disorders.

Monocyte-predominant engraftment, cytokine levels and early transplant-related complications in pediatric hematopoietic stem cell recipients

Myeloablative conditioning is a well‐established procedure that precedes hematopoietic stem cell transplantation (HSCT), particularly in pediatric patients. In the period directly following transplantation, several factors may contribute to complications that lead to the activation or damage of endothelial cells, involved in the pathogenesis of vascular endothelial syndromes (VES). However, to date, sufficiently specific and sensitive diagnostic markers for the various forms of VES have not been identified. This was a retrospective single‐center study of patients who underwent allogeneic HSCT. For this cohort of patients, parameters including type of engraftment, donor characteristics, and cytokine production were measured and correlated with a high prevalence of short‐term complications after HSCT. The aim of this study was to identify specific parameters useful for improving diagnostics and predicting adverse effects in VES. We confirmed that monocyte‐predominant engraftment was related to a higher risk for an early transplant‐related complication termed sinusoidal obstruction syndrome (SOS). The increased production of specific cytokines, in particular RANTES, represents a marker associated with prevalent engraftment. In addition, patients undergoing prophylaxis with defibrotide had “classical” engraftment, a common cytokine profile and a lower incidence of life‐threatening transplant‐related complications. The beneficial effect of defibrotide might be a starting point for developing selective prophylaxis for patients with monocyte engraftment to prevent severe early transplant‐related complications.

The onset of vascular endothelial syndromes after hematopoietic stem cell transplantation is significantly associated with monocyte‐predominant engraftment (P < 0.0001). The increased production of specific cytokines, in particular RANTES, represents a marker associated with monocyte‐predominant engraftment. There is close association between the prophylactic administration of defibrotide, a powerful endothelial protector, and the incidence of vascular endothelial syndromes (P < 0.0001). Given the high cost of defibrotide, selective prophylaxis may be considered for patients with extremely high values of RANTES or with monocyte engraftment.

A Heterozygous CFHR3-CFHR1 Gene Deletion in a Pediatric Patient With Transplant-associated Thrombotic Microangiopathy Who was Treated With Eculizumab

Complement system dysregulation, such as complement Factor H (CFH) autoantibodies and deletions in CFH-related (CFHR) genes 3 and 1, might cause transplant-associated thrombotic microangiopathy (TA-TMA). The use of eculizumab, a terminal complement inhibitor, could be a targeted therapy for TA-TMA. We report a 1-year-old girl who developed TA-TMA, just after autologous peripheral blood stem cell transplantation in neuroblastoma therapy. Eculizumab improved TA-TMA. Investigation for the complement alternative pathway showed a heterozygous CFHR3-CFHR1 gene deletion, which is involved in complement activation. The patient might develop TA-TMA as a result of complement regulatory gene mutation.

Transplant-Associated Thrombotic Microangiopathy Is a Multifactorial Disease Unresponsive to Immunosuppressant Withdrawal

Transplant-associated thrombotic microangiopathy (TA-TMA) after allogeneic hematopoietic cell transplantation (HCT) has not been well characterized in large population studies with clinically adjudicated cases. We performed a retrospective cohort study of adults who underwent allogeneic HCT between 2006 and 2015 to determine the incidence of and risk factors for TA-TMA and to describe its natural history and response to immunosuppressant withdrawal management. Among 2145 patients in this study, 192 developed TA-TMA with a cumulative incidence of 7.6% by 100days post-transplant. Independent pretransplant risk factors included the receipt of a second (or third) allogeneic HCT, HLA-mismatched donor, and myeloablative conditioning with or without total body irradiation; post-transplant risk factors included the antecedent development of acute graft-versus-host disease, diffuse alveolar hemorrhage, bacteremia, invasive aspergillosis, BK viremia, and higher sirolimus trough level. Among TA-TMA patients 27% achieved hematologic resolution and 57% remained alive as of 90days after diagnosis. Antecedent risk factors stratified patients into different survival groups, and immunosuppressant withdrawal alone did not improve patient outcomes. In conclusion, TA-TMA is a heterogenous disease that occurs after allogeneic transplantation. Management with immunosuppressant withdrawal does not impact patient outcomes. Until further evidence becomes available, the management of TA-TMA should focus on the treatment of underlying diseases.

Emerging Concepts in Hematopoietic Stem Cell Transplantation-Associated Renal Thrombotic Microangiopathy and Prospects for New Treatments

Thrombotic microangiopathy associated with hematopoietic stem cell transplantation (HSCT-TMA) is a well-recognized complication of HSCT that has a high risk for death. Even in patients who survive, HSCT-TMA is associated with long-term morbidity and chronic organ injury. HSCT-TMA is a multisystem disease that often affects the kidneys. Renal manifestations of HSCT-TMA include reduced glomerular filtration rate, proteinuria, and hypertension. Understanding of the pathophysiology of HSCT-TMA has expanded in the last decade. Endothelial injury plays a major role. Recent studies also suggest involvement of complement activation. HSCT-TMA has also been considered by some to be an endothelial variant of graft-versus-host disease. Understanding the pathophysiology of HSCT-TMA and its association with activation of the complement system may aid in developing novel therapeutic options. In this review, we summarize current knowledge focusing on epidemiology and prognosis, evidence of complement activation, and endothelial injury; the possible link to graft-versus-host disease; and treatment options for HSCT-TMA.

Eculizumab for transplant-associated thrombotic microangiopathy in adult allogeneic stem cell transplant recipients

OBJECTIVE

To evaluate response rates and survival in adults with transplant-associated thrombotic microangiopathy (TA-TMA) after allogeneic hematopoietic stem cell transplantation (HSCT) who were treated with eculizumab (ECU).

METHODS

Patients were identified retrospectively and data collected through HSCT and pharmacy databases.

RESULTS

Ten patients with TA-TMA after allogeneic HSCT were treated with ECU between 2013 and 2016. TA-TMA was diagnosed at a median of 93 days post-HSCT. Organ-specific injury was documented in all ten patients at time of TA-TMA diagnosis, the most common being renal dysfunction (90%). Acute GVHD (70%) and active infection (80%) were common at time of diagnosis. The median time to ECU initiation from TA-TMA diagnosis was 4 days. Seven patients received ECU as first-line therapy in combination with other treatment modalities, while three patients were treated with ECU as second-line therapy. ECU was well tolerated with the exception of one case of severe skin rash leading to discontinuation. ECU achieved an overall hematologic response rate of 70% and an overall survival rate of 60%. One patient achieved a complete response with corresponding organ recovery.

CONCLUSION

Early initiation of ECU may not alter the disease process enough to restore organ function, but it may prolong survival.

Early Increase in Complement Terminal Pathway Activation Marker sC5b-9 Is Predictive for the Development of Thrombotic Microangiopathy after Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is a multifactorial complication, and its prediction is largely unresolved. Our aim was to analyze changes of complement profile after HSCT to identify potential markers of TA-TMA development. Thirty-three consecutive pediatric patients (9.6 ± 4.4 years old) who underwent allogeneic HSCT due to malignant (n = 17) or nonmalignant (n = 16) indications were included in this study. Graft-versus-host disease (GVHD) was diagnosed using Glucksberg criteria, viral reactivation was monitored, 5 different TA-TMA diagnostic criteria were applied, and all important clinical and laboratory parameters of TA-TMA activity were registered. Complement pathway activities, components and terminal pathway activation marker (sC5b-9) levels were systematically measured before transplantation and on days 28, 56, and 100 after HSCT. During the first 100 days after HSCT, 1 of 33 patients died (day 50, multiple organ failure), whereas 10 subjects met the criteria for TA-TMA, typically on day 61 (range, 16 to 98 days). TA-TMA was preceded by acute GVHD in 3 of 10 patients, by viral reactivation in 2 of 10, or by both in 4 of 10 cases. Baseline sC5b-9 levels did not differ in patients without (200 [interquartile range, 144 to 266] ng/mL), or with (208 [interquartile range, 166 to 271] ng/mL) subsequent TA-TMA; however, on day 28 significant differences were observed (201 [interquartile range, 185 to 290] ng/mL versus 411 [interquartile range, 337 to 471] ng/mL; P = .004). Importantly, all 10 patients with TMA showed increase in sC5b-9 level from baseline level to day 28, whereas in patients without TMA the same tendency was observed for only 9 of 23 patients (P = .031). No additional complement parameters were closely associated with the development of TA-TMA. Development of TA-TMA occurred in 30% of our patients, typically after GVHD and/or viral reactivation. However, early raise of sC5b-9 activation marker was predictive for later development of TA-TMA, and should therefore be considered as an alarming sign necessitating a careful monitoring of all TA-TMA activity markers. Further studies enrolling a higher number of patients are necessary to determine if terminal pathway activation is an independent predictor of TA-TMA.

Thrombotic microangiopathy with concomitant GI aGVHD after allogeneic hematopoietic stem cell transplantation: Risk factors and outcome

OBJECTIVES

To explore the possible risk factors for the occurrence and mortality of thrombotic microangiopathy (TMA) with concomitant acute graft-vs-host disease (aGVHD) and to investigate outcomes and treatments of this disorder after allo-HSCT.

METHODS

Fifty cases diagnosed with TMA with concomitant aGVHD and 150 controls were identified from a cohort composed of 3992 patients who underwent allo-HSCT from 2008 to 2016.

RESULTS

Grade III-IV aGVHD (P = .000), acute kidney injury (AKI) (P = .033), and hypertension (P = .028) were significant independent risk factors associated with the occurrence of TMA with concomitant aGVHD. A haptoglobin level below normal (P = .013), a maximum volume of diarrhea >2500 mL/d (P = .015), and bloody diarrhea (P = .049) were significant markers for death in both univariate and multivariate analyses. Patients diagnosed with TMA with concomitant aGVHD had a lower overall survival (OS), a higher non-relapse mortality (NRM), but a lower risk of relapse.

CONCLUSIONS

Thrombotic microangiopathy with concomitant aGVHD is a significant complication after allo-HSCT, with a worse outcome, including significantly lower OS and higher NRM. There are specific risk factors associated with occurrence and mortality of this complication.