Small vessels, big trouble in the kidneys and beyond: hematopoietic stem cell transplantation–associated thrombotic microangiopathy

De Novo Thrombotic Microangiopathy in Renal Transplant Patients

OBJECTIVES

Thrombotic microangiopathy is a form of renal capillary injury possibly associated with calcineurin inhibitor toxicity, acute humoral rejection, infections, and recurrent diseases. Here, we examined its incidence in patients diagnosed with acute and chronic active humoral rejection, polyomavirus nephropathy, acute cellular rejection, and immunoglobulin A recurrence.

MATERIALS AND METHODS

In total, 272 renal allograft recipients who met the inclusion criteria were reevaluated for presence of renal thrombotic microangiopathy. Thrombotic microangiopathy diagnosis was established by clinical, laboratory, and histologic features. C4d expression in peritubular capillaries was determined. Clinical data were collected from medical records.

RESULTS

Of 272 patients (mean age of 42.8 ± 12.7 years), only 74 patients (27.2%) had de novo thrombotic microangiopathy, which was found in 30/90 patients (33.3%) with acute humoral rejection, 9/51 (17.6%) with acute cellular rejection, 22/53 (41.5%) with chronic active humoral rejection, 10/55 (18.2%) with polyomavirus nephropathy, and 3/23 (13%) with immunoglobulin A nephropathy. Significant differences were shown between therapy type and thrombotic microangiopathy development (P = .02). Patients who received cyclosporine (38.5%) tended to show higher incidence of thrombotic microangiopathy than patients who received tacrolimus (20.7%) or sirolimus (7.7%). Patients with C4d-positive acute humoral (97.6% vs 2.4%) and chronic active humoral rejection (68.2% vs 31.8%) had greater incidence of thrombotic microangiopathy versus those who were C4d-negative. Graft loss was significantly higher in C4d-positive than in C4d-negative thrombotic microangiopathy groups (P < .001). Overall 1-, 3-, and 5-year graft survival was 94%, 85%, and 85% versus 83%, 51%, and 51% in thrombotic microangiopathy-negative versus thrombotic microangiopathy-positive patients (P < .001).

CONCLUSIONS

Acute humoral rejection and chronic active humoral rejection were the most common and therefore most important causes of de novo thrombotic microangiopathy in renal transplant patients. Its presence in the renal allograft biopsy should arouse suspicion for underlying acute or chronic active humoral rejection.

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.

Secondary thrombotic microangiopathy and eculizumab: A reasonable therapeutic option

Understanding the role of the complement system in the pathogenesis of atypical haemolytic uraemic syndrome and other thrombotic microangiopathies (TMA) has led to the use of anti-complement therapy with eculizumab in these diseases, in addition to its original use in patients with paroxysmal nocturnal haemoglobinuria andatypical haemolytic uraemic syndrome. Scientific evidence shows that both primary and secondary TMAs with underlying complement activation are closely related. For this reasons, control over the complement system is a therapeutic target. There are 2scenarios in which eculizumab is used in patients with TMA: primary or secondary TMA that is difficult to differentiate (including incomplete clinical presentations) and complement-mediated damage in various processes in which eculizumab proves to be efficacious. This review summarises the evidence on the role of the complement activation in the pathophysiology of secondary TMAs and the efficacy of anti-complement therapy in TMAs secondary to pregnancy, drugs, transplant, humoral rejection, systemic diseases and glomerulonephritis. Although experience is scarce, a good response to eculizumab has been reported in patients with severe secondary TMAs refractory to conventional treatment. Thus, the role of the anti-complement therapy as a new treatment option in these patients should be investigated.

Acute kidney injury and electrolyte disorders in the critically ill patient with cancer

PURPOSE OF REVIEW

Patients with cancer increasingly make up a significant proportion of patients receiving care in the intensive care unit (ICU). Acute kidney injury and cancer-associated electrolyte disorders are encountered in many of these patients and can significantly impact both short-term and long-term outcomes.

RECENT FINDINGS

Advances in chemotherapeutic regimens as well as in our understanding of cancer-associated kidney disease highlight the need for specialized knowledge of the unique causes and therapies required in this subset of critically ill patients. This is especially the case as targeted cancer therapies may have off-target effects that need to be recognized in a timely manner.

SUMMARY

This review outlines key knowledge areas for critical care physicians and nephrologists caring for patients with cancer and associated kidney issues such as acute kidney injury and electrolyte disorders. Specifically, understanding kidney-specific effects of new chemotherapeutic approaches is outlined, and provides an up-to-date compendium of these effects.

Successful Recombinant Thrombomodulin Treatment for Thrombotic Microangiopathy After Liver Transplantation: A Case Report

Transplant-associated thrombotic microangiopathy (TA-TMA) is a rare but severe complication after liver transplantation. In contrast to other thrombotic microangiopathies, treatment for TA-TMA has yet to be clarified. A 52-year-old male patient with liver cirrhosis due to hepatitis C underwent split liver transplantation from a deceased donor. His clinical course was without complication until 4 days after transplantation, when he experienced impaired consciousness, hemolytic anemia with fragmented erythrocytes, and marked thrombocytopenia. TA-TMA was diagnosed, and recombinant thrombomodulin was administered for 4 days. The patient's clinical symptoms and laboratory data rapidly improved. He has been followed up for 6 months and has not shown any complications. The pathogenesis of TA-TMA is endothelial damage in the vasculature. Recombinant thrombomodulin, an endothelial cell-protecting agent, is a promising new therapeutic choice for TA-TMA after liver transplantation.

Changes in Glomerular Filtration Rate and Impact on Long-Term Survival among Adults after Hematopoietic Cell Transplantation: A Prospective Cohort Study

BACKGROUND AND OBJECTIVES

Kidney injury is a significant complication for patients undergoing hematopoietic cell transplantation (HCT), but few studies have prospectively examined changes in GFR in long-term survivors of HCT. We described the association between changes in GFR and all-cause mortality in patients up to 10 years after HCT.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a prospective, observational cohort study of adult patients undergoing HCT at the Fred Hutchinson Cancer Center in Seattle, Washington from 2003 to 2015. Patients were followed from baseline, before conditioning therapy, until a maximum of 10 years after transplant. We used Cox proportional hazard models to examine the association between creatinine eGFR and all-cause mortality. We used time-dependent generalized estimating equations to examine risk factors for decreases in eGFR.

RESULTS

A total of 434 patients (median age, 52 years; range, 18-76 years; 64% were men; 87% were white) were followed for a median 5.3 years after HCT. The largest decreases in eGFR occurred within the first year post-transplant, with the eGFR decreasing from a median of 98 ml/min per 1.73 m2 at baseline to 78 ml/min per 1.73 m2 by 1 year post-HCT. Two thirds of patients had an eGFR<90 ml/min per 1.73 m2 at 1 year after transplant. When modeled as a continuous variable, as eGFR declined from approximately 60 ml/min per 1.73 m2, the hazard of mortality progressively increased relative to a normal eGFR of 90 ml/min per 1.73 m2 (P<0.001). For example, when compared with an eGFR of 90 ml/min per 1.73 m2, the hazard ratios for eGFR of 60, 50, and 40 ml/min per 1.73 m2 are 1.15 (95% confidence interval, 0.87 to 1.53), 1.68 (95% confidence interval, 1.26 to 2.24), and 2.67 (95% confidence interval, 1.99 to 3.60), respectively. Diabetes, hypertension, acute graft versus host disease, and cytomegalovirus infection were independently associated with a decline in GFR, whereas calcineurin inhibitor levels, chronic graft versus host disease, and albuminuria were not.

CONCLUSIONS

Adult HCT recipients have a high risk of decreased eGFR by 1 year after HCT. Although eGFR remains fairly stable thereafter, a decreased eGFR is significantly associated with higher risk of mortality, with a progressively increased risk as eGFR declines.

Brain microvascular endothelial cells exhibit lower activation of the alternative complement pathway than glomerular microvascular endothelial cells

Atypical hemolytic uremic syndrome (aHUS) and bone marrow transplantation-associated thrombotic microangiopathy (TA-TMA) are associated with excessive activation of the alternative complement pathway (AP) and with severe renal, but rarely cerebral, microvascular damage. Here, we compared AP activation and regulation in human glomerular and brain microvascular endothelial cells (GMVECs and BMVECs, respectively) unstimulated or stimulated by the proinflammatory cytokine, tumor necrosis factor (TNF). Compared with GMVECs and under both experimental conditions, BMVECs had increased gene expression of the AP-related genes C3, CFB, and C5 and decreased expression of CFD This was associated with increased expression in BMVECs (relative to GMVECs) of the genes for surface and soluble regulatory molecules (CD46, THBD, CD55, CFI, and CFH) suppressing formation of the AP C3 and C5 convertases. Of note, unlike GMVECs, BMVECs generated extremely low levels of C3a and C5a and displayed decreased activation of the AP (as measured by a lower percentage of Ba generation than GMVECs). Moreover, BMVECs exhibited increased function of CD141, mediating activation of the natural anticoagulant protein C, compared with GMVECs. We also found that the C3a receptor (C3aR) is present on both cell types and that TNF greatly increases C3AR1 expression in GMVECs, but only slightly in BMVECs. Higher AP activation and C3a generation in GMVECs than in BMVECs, coupled with an increase in C3aR production in TNF-stimulated GMVECs, provides a possible explanation for the predominance of renal damage, and the absence of cerebral injury, in individuals with episodes of aHUS and TA-TMA.

Treatment of thrombotic microangiopathy with a focus on new treatment options

The thrombotic microangiopathies (TMA) are a heterogeneous group of disorders, characterized by microangiopathic haemolytic anaemia with red cell fragmentation, thrombocytopenia and signs of organ dysfunction due to disturbed microcirculation. Current laboratory methods can be used to better distinguish some of these entities. Organ dysfunction can be severe and life-threatening, and immediate start of sufficient therapy is necessary to avoid permanent damage or death. The therapeutic options, however, are often limited to symptomatic measures, and are not standardized or based on high scientific evidence. During the preceding years, not only considerable progress has been made in better diagnosis of TMA, but also new therapeutic strategies have been established. Initial treatment still is based on plasma exchange and symptomatic measures to protect organ function. New concepts (immunosuppression, targeted anti-von Willebrand factor or anti-complement therapy, replacement with recombinant enzymes) are discussed in this article.

Thrombotic microangiopathy following haematopoietic stem cell transplant

Thrombotic microangiopathy is a potentially lethal complication of haematopoietic stem cell (bone marrow) transplantation. The pathophysiology is incompletely understood, although endothelial damage appears to be central. Platelet activation, neutrophil extracellular traps and complement activation appear to play key roles. Diagnosis may be difficult and universally accepted diagnostic criteria are not available. Treatment remains controversial. In some cases, withdrawal of calcineurin inhibitors is adequate. Rituximab and defibrotide also appear to have been used successfully. In severe cases, complement inhibitors such as eculizumab may play a valuable role. Further research is required to define the pathophysiology and determine both robust diagnostic criteria and the optimal treatment.

Acute phase after haematopoietic stem cell transplantation

The transplantation of allogeneic or autologous haematopoietic stem cells is an established treatment for many malignant and non-malignant diseases of the bone marrow. Intensive cytoreductive regimens administered before transplantation induce prolonged and severe cytopenia of all haematopoietic lineages. Thrombocytopenia leads to an increased risk of bleeding, which may be further aggravated by consumption of plasmatic factors as a result of tumour lysis or after antibody administration. At the same time, patients after transplantation are also at increased risk of thrombotic complications. Endothelial damage induced by radio-and chemotherapy, indwelling catheters, prolonged immobilization and a high incidence of systemic infection all contribute to the frequent occurrence of thromboembolic events in this population.

This review discusses the incidence and risk factors for haemorrhagic and thrombotic complications after stem cell transplantation. Special emphasis is given to complications occurring specifically in the context of transplantation such as diffuse alveolar haemorrhage, haemorrhagic cystitis, veno-occlusive disease, and transplant associated microangiopathy.

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.

Plasma exchange in thrombotic microangiopathies (TMAs) other than thrombotic thrombocytopenic purpura (TTP)

Thrombotic microangiopathies (TMAs) are a diverse group of disorders that are characterized by common clinical and laboratory features. The most commonly thought-of TMA is thrombotic thrombocytopenic purpura (TTP). Because of the marked improvement in patient mortality associated with the use of therapeutic plasma exchange (TPE) in TTP, this therapy has been applied to all of the TMAs. The issue, however, is that the pathophysiology varies and in many instances may represent a disorder of the endothelium and not the blood; in some cases, the pathophysiology is unknown. The use of TPE is further obscured by a lack of strong supporting literature on its use, with most consisting of case series and case reports; controlled or randomized controlled trials are lacking. Evidence supporting the use of TPE in the treatment of TMAs (other than TTP and TMA-complement mediated) is lacking, and therefore its role is uncertain. With the greater availability of genetic testing for mutations involving complement regulatory genes and complement pathway components, there seems to be a percentage of TMA cases, other than TMA-complement mediated, in which complement pathway mutations are involved in some patients. The ability of TPE to remove abnormal complement pathway components and replace them with normal components may support its use in some patients with TMAs other than TTP and TMA-complement mediated.

Successful Treatment of Transplant Associated Thrombotic Microangiopathy (TA-TMA) with Low Dose Defibrotide

Transplant associated microangiopathy (TA-TMA) is a potentially serious complication of stem cell transplantation. Though stopping calcineurin/mTOR inhibitor is the first step in managing TA-TMA, this is not always adequate. The pathophysiology of TA-TMA is different from microangiopathy seen in other settings. Many drugs have been used in TA-TMA with modest responses. Defibrotide has been explored in TA-TMA in the past with good results. However, its availability is erratic and cost of therapy very high. Hence its routine use in low middle income country (LMIC) is financially demanding. We report the use of low dose defibrotide safely and successfully in this case series. This is pertinent more to LMIC's and warrants prospective evaluation.

Plasma levels of complement activation fragments C3b and sC5b-9 significantly increased in patients with thrombotic microangiopathy after allogeneic stem cell transplantation

Transplantation-associated thrombotic microangiopathy (TA-TMA) is an uncommon but severe complication in patients undergoing allogeneic stem cell transplantation (allo-SCT). However, the mechanism is unclear. From 2011 to 2014, 20 patients with TA-TMA, 20 patients without, and 54 patients with various other complications, including veno occlusive disease (VOD), graft-versus-host disease (GVHD), and infection, were recruited in the study. Plasma vWF antigen (vWFAg), vWF activity (vWFAc), and ADAMTS13 activity were determined in these patients by ELISAs and FRETS-vWF73 assay, respectively. Plasma C3b, sC5b-9, and CH50 were also determined by ELISAs. Plasma levels of C3b were significantly increased in patients with either TA-TMA (p < 0.0001) or GVHD (p < 0.01). Plasma sC5b-9 and CH50 levels in patients with TA-TMA were also significantly increased (p < 0.001). Plasma ADAMTS13 activity was lower in patients with VOD, but normal with other complications. Both plasma vWFAg and vWFAc levels were not elevated in patients with TA-TMA or VOD compared with those of other groups. Complement activation likely via an alternative pathway (increased C3b, sC5b-9, and CH50) may play a role in the pathogenesis of TA-TMA. ADAMTS13 activity is reduced in VOD, but the ADAMTS13/vWF axis appears to be unaffected in patients with TA-TMA.

Eculizumab in secondary atypical haemolytic uraemic syndrome

Background. Complement dysregulation occurs in thrombotic microangiopathies (TMAs) other than primary atypical haemolytic uraemic syndrome (aHUS). A few of these patients have been reported previously to be successfully treated with eculizumab.

Methods. We identified 29 patients with so-called secondary aHUS who had received eculizumab at 11 Spanish nephrology centres. Primary outcome was TMA resolution, defined by a normalization of platelet count (>150 × 10⁹/L) and haemoglobin, disappearance of all the markers of microangiopathic haemolytic anaemia (MAHA), and improvement of renal function, with a ≥25% reduction of serum creatinine from the onset of eculizumab administration.

Results. Twenty-nine patients with secondary aHUS (15 drug-induced, 8 associated with systemic diseases, 2 with postpartum, 2 with cancer-related, 1 associated with acute humoral rejection and 1 with intestinal lymphangiectasia) were included in this study. The reason to initiate eculizumab treatment was worsening of renal function and persistence of TMA despite treatment of the TMA cause and plasmapheresis. All patients showed severe MAHA and renal function impairment (14 requiring dialysis) prior to eculizumab treatment and 11 presented severe extrarenal manifestations. A rapid resolution of the TMA was observed in 20 patients (68%), 15 of them showing a ≥50% serum creatinine reduction at the last follow-up. Comprehensive genetic and molecular studies in 22 patients identified complement pathogenic variants in only 2 patients. With these two exceptions, eculizumab was discontinued, after a median of 8 weeks of treatment, without the occurrence of aHUS relapses.

Conclusion. Short treatment with eculizumab can result in a rapid improvement of patients with secondary aHUS in whom TMA has persisted and renal function worsened despite treatment of the TMA-inducing condition.

Central nervous system complications after allogeneic hematopoietic stem cell transplantation

Allogenic hematopoietic stem cell transplant (alloSCT) is a potentially curative modality of treatment for patients with hematological malignancies. However, CNS complications following transplant pose a risk to survival of the patients. Early recognition and management of these complications are crucial to reduce morbidity and mortality of patients following transplant. Early CNS complications associated with alloSCT are infection, cerebrovascular events, chemotherapy and radiation-induced toxicities while late complications include post-transplant lymphoproliferative disorder, CNS relapse of underlying malignancy and viral and fungal infections. Development of graft-versus-host disease can further increase the risk of CNS complications and outcomes after alloSCT. Strategies aimed to reduce the risk of CNS complications and early management may ameliorate the morbidity and mortality in transplant recipients.

Delayed Development of Hemolytic Anemia with Fragmented Red Blood Cells and Cardiac and Renal Impairments after High-Dose Chemotherapy and Autologous Hematopoietic Stem Cell Transplantation for Malignant Lymphoma

Among 42 consecutive patients with malignant lymphoma who underwent high-dose chemotherapy (HDC) followed by autologous hematopoietic stem cell transplantation (AHSCT), 5 developed hemolytic anemia with fragmented red blood cells (HA-FrRBCs) on days 87-125 (median 107) of AHSCT. Nadir Hb levels ranged between 5.0 and 6.4 g/dL with 2.2-5.6% FrRBCs. All patients developed grade ≥3 hypoxia and heart failure, and 4 developed grade ≥3 hypertension. The ejection fraction of the left ventricle assessed by echocardiography was significantly reduced in 3 patients. Peak creatinine levels were >4 times above the baseline and estimated glomerular filtration rates were reduced to <30 mL/min/1.73 m2. One patient received plasma exchange, while the remaining 4 responded to treatment with diuretics and cardiovascular agents. Hematological parameters normalized within a median duration of 91 days after the development of HA-FrRBCs. Renal and cardiac functions gradually improved, even though renal function did not return to the baseline. HA-FrRBCs associated with cardiac and renal impairments may represent a thrombotic microangiopathy syndrome and are a delayed complication of HDC/AHSCT. The close monitoring of laboratory abnormalities and persistent treatment with cardiovascular agents and diuretics are the mainstay for the management of this condition.

Team-based approach to identify cardiac toxicity in critically ill hematopoietic stem cell transplant recipients

INTRODUCTION

We observed pulmonary hypertension (PH), pericardial effusions, and left ventricular systolic dysfunction (LVSD) in multiple critically ill hematopoietic stem cell transplant (HSCT) recipients. We implemented routine structured echocardiography screening for HSCT recipients admitted to the pediatric intensive care unit (PICU) using a standardized multidisciplinary process.

METHODS

HSCT recipients admitted to the PICU with respiratory distress, hypoxia, shock, and complications related to transplant-associated thrombotic microangiopathy were screened on admission and every 1-2 weeks thereafter. Echocardiography findings requiring intervention and/or further screening included elevated right ventricular pressure, LVSD, and moderate to large pericardial effusions. All echocardiograms were compared to the patient's routine pretransplant echocardiogram.

RESULTS

Seventy HSCT recipients required echocardiography screening over a 3-year period. Echo abnormalities requiring intervention and/or further screening were found in 35 (50%) patients. Twenty-four (34%) patients were noted to have elevated right ventricular pressure; 14 (20%) were at risk for PH, while 10 (14%) had PH. All patients with PH were treated with pulmonary vasodilators. LVSD was noted in 22 (31%) patients; 15/22 (68%) received inotropic support. Moderate to large pericardial effusions were present in nine (13%) patients, with six needing pericardial drain placement.

DISCUSSION

Echocardiographic abnormalities are common in critically ill HSCT recipients. Utilization of echocardiogram screening may allow for early detection and timely intervention for cardiac complications in this high-risk cohort.

Kidney Disease in Cancer Survivors: Focus on Hematopoietic Stem Cell Transplantation

Kidney disease and hypertension are common among children and adults with cancer, including those undergoing hematopoietic stem cell transplantation (HSCT). While survival has improved over time for patients receiving a HSCT, acute kidney injury (AKI) and chronic kidney disease (CKD) remain associated with significant morbidity and mortality. The mechanisms leading to kidney disease in this population are likely multifactorial and include chemotherapy, other nephrotoxic medications, and infections. Nevertheless, we still do not completely understand why such a large proportion of patients develop kidney disease after HSCT. The growing field of onco-nephrology allows oncologists, transplant providers, and nephrologists to learn about disease processes and treatments relevant to their respective patient populations. Accordingly, we are learning that several mechanisms of injury affecting HSCT recipients also occur in general nephrology and in kidney transplant recipients. For example, complement dysregulation leading to atypical hemolytic uremic syndrome parallels HSCT-associated thrombotic microangiopathy and BK virus nephropathy occurring after kidney transplant can also lead to CKD in HSCT recipients. This review focuses on thrombotic microangiopathy and BK virus infection as potential causes of AKI and CKD after HSCT, which are currently thought to be idiopathic. These diagnoses require a high index of suspicion, emphasizing the importance of close attention to blood pressure, proteinuria, and the measurement and estimation of kidney function in patients undergoing HSCT.

In vitro evidence of complement activation in transplantation-associated thrombotic microangiopathy

Transplantation-associated thrombotic microangiopathy is associated with complement activation in vitro.This data further supports the use of eculizumab for the treatment of patients with TA-TMA.

Severe transplant-associated thrombotic microangiopathy in patients with hemoglobinopathies

Incidence and severity of transplant-associated thrombotic microangiopathy (TA-TMA) in patients with hemoglobinopathies receiving hematopoietic cell transplant is unknown. We report the outcomes for two patients with TA-TMA who received eculizumab. A 2.5-year-old male with sickle cell disease developed TA-TMA-associated pericardial tamponade, severe hypertension, and acute kidney injury 2 months after transplant. A 7-year-old female with β-thalassemia major developed TA-TMA-related acute kidney injury, severe hypertension, and seizures at 6 months after transplant. Both patients progressed to chronic kidney disease (CKD). In patients with hemoglobinopathies, preexisting endothelial dysfunction may place them at a greater risk for TA-TMA and subsequent CKD.

Thrombotic Microangiopathy With Granulomatosis Interstitial Nephritis in an Allogenic Bone Marrow Transplant Patient: A Case Report and Review of the Literature

Transplant-associated thrombotic microangiopathy (TA-TMA) is a rare complication of hematopoietic stem cell transplantation (HSCT) with variable presentations. TA-TMA has often been described as a diagnosis of exclusion but a renal biopsy is rarely pursued to confirm the diagnosis, an essential step for our patient with renally limited TMA. We report a case report from the onconephrology clinic and review the literature associated with TA-TMA as it relates to diagnosis and treatment. A 45-year-old woman with acute myeloid leukemia and stage 3 chronic kidney disease underwent a matched unrelated donor allogenic HSCT. Postoperatively, she developed gastrointestinal graft versus host disease (GvHD) and was treated with tacrolimus, sirolimus, budesonide, and beclomethasone. Following discharge, she developed uncontrolled hypertension and required losartan, amlodipine, carvedilol, clonidine patch, and hydralazine as needed. On day 180 post-transplant, she developed lower extremity edema and acute kidney injury (AKI) with creatinine increasing to 2 mg/dL. On day 480 post-transplant, she developed worsening thrombocytopenia, anemia, new hematuria, left flank pain, and worsening renal function with creatinine peaking to 6 mg/dL. Peripheral smear revealed no schistocytes, lactate dehydrogenase of 265 mg/dL, and urinalysis with 100 mg/dL protein. ADAMTS 13 activity was normal (92%) and no inhibitor was detected. She became anuric and was started on hemodialysis. Renal biopsy revealed glomerular changes consistent with TA-TMA. During HSCT, systemic vascular endothelial injury triggers microangiopathic hemolytic anemia, platelet consumption, injury of glomerular endothelial cells and fibrin occluded renal capillaries. Thus, TA-TMA should be considered in HSCT patients with elevated LDH, proteinuria, hypertension, and AKI. However, a diagnosis is difficult to confirm without a renal biopsy. Treatment involves discontinuing potentially toxic agents such as calcineurin inhibitors and sirolimus, prescribing adequate antimicrobial treatment, and using renal replacement therapy if needed. A renal biopsy early in the course of disease not only confirms the diagnosis, but may limit the extent of disease.

A Complete Histologic Approach to Gastrointestinal Biopsy From Hematopoietic Stem Cell Transplant Patients With Evidence of Transplant-Associated Gastrointestinal Thrombotic Microangiopathy

CONTEXT

- Transplant-associated thrombotic microangiopathy is a serious complication of hematopoietic stem cell transplant that may progress to multi-organ dysfunction. Transplant-associated thrombotic microangiopathy may involve the intestinal vasculature (intestinal transplant-associated thrombotic microangiopathy [iTMA]), causing patients to experience debilitating symptoms of ischemic colitis, including disproportionately severe abdominal pain and gastrointestinal bleeding, requiring heavy narcotic use and frequent transfusion support. Pathophysiology remains poorly investigated but may include endothelial damage mediated by inflammatory markers and the complement system. Endoscopy of hematopoietic stem cell transplant patients often produces biopsy samples, in which mucosal lamina propria capillaries are sufficient for an evaluation of iTMA features.

OBJECTIVE

- To provide a detailed review of histologic features of iTMA.

DATA SOURCES

- We conducted a systematic review of studies assessing histologic features of iTMA. Studies were identified by PubMed search and included a cohort study performed by our group.

CONCLUSIONS

- The histologic hallmark of iTMA is endothelial cell injury that leads to hemorrhage and thrombosis of the capillaries. Histologic features include endothelial cell swelling, endothelial cell separation, perivascular mucosal hemorrhage, intraluminal schistocytes, intraluminal fibrin, intraluminal microthrombi, loss of glands, and total denudation of mucosa. Identification of features consistent with iTMA has immediate implications for clinical management that could potentially improve outcome and survival.

[Allogeneic hematopoietic stem cell transplantation associated thrombotic microangiopathy: 16 cases report and literature review]

目的

分析异基因造血干细胞移植（allo-HSCT）相关血栓性微血管病（TA-TMA）患者临床特征、疗效及转归。

方法

回顾性分析2013年1月至2015年6月于苏州大学附属第一医院接受allo-HSCT后发生TA-TMA的16例患者临床资料。

结果

纳入研究的852例allo-HSCT患者，16例（1.9%）发生TA-TMA，中位随访时间14个月，1年累计发生率为（2.3±0.6）%。16例患者中，男7例，女9例，中位年龄41(12~54）岁，中位发病时间为移植后72(21~525) d, PLT中位数为20(11~36）×10⁹/L，HGB中位数为74(56~99）g/L，LDH中位水平为762(309~1 049) U/L，外周血破碎红细胞比例中位数为3%（2%~13%），所有患者ADAMTS13活性均>60%。10例出现精神症状，7例肌酐水平升高。TA-TMA确诊后的主要治疗措施为钙调磷酸酶体抑制剂的减停、激素及血浆置换疗法，8例经治疗后病情得以控制，治疗有效；8例患者治疗无效死亡。治疗无效组8例患者中5例合并急性肠道移植物抗宿主病（GVHD），治疗有效组患者无一例合并肠道GVHD；8例治疗无效患者中5例外周血破碎红细胞比例>5%，而治疗有效组破碎红比例最高为4%；治疗无效患者LDH及肌酐中位水平均高于治疗有效组，分别为826(674~1 310) U/L对636(309~941）U/L及127(70~215）µmol/L对56(22~101）µmol/L。

结论

TA-TMA是allo-HSCT后的一类严重并发症，可导致全身多器官功能损伤，即使采取治疗早期病死率仍较高，疗效与病情轻重及有无并发症有关。

[Thrombotic microangiopathy and cancer]

Thrombotic microangiopathy (TMA) is a group of disorders characterized by mechanical hemolytic anemia with thrombocytopenia and an ischemic organic lesion of variable and potentially fatal importance affecting mostly the kidneys and the brain with histologically a disseminated and occlusive microvasculopathy. The incidence of TMA represents 15% of acute kidney failure in oncological setting, largely due to the introduction of anti-angiogenic agents over the past decade. It may be more rarely related to cancer itself. The iatrogenic TMA can be classified into 2 types: The type I, secondary to chemotherapy (mitomycinC, gemcitabine), exposes to a chronic dose-dependent renal injury as well as an increase in morbidity and mortality; iatrogenic type II, secondary to anti-angiogenic agents', results in a dose-independent renal involvement and renal functional recovery is usual when the drug is discontinued. There is no randomized controlled trial to establish EBM-type management in TMA support. However, complement activation pathways and regulatory factors analyses allowed us to understand the mechanisms of endothelial lesions. As a result, the current trend includes the use of immunosuppressive agents in recurrent or plasmapheresis-refractory MAT.

Clinical dissection of thrombotic microangiopathy

Differential treatment strategies are applied in thrombotic microangiopathy (TMA) according to the sub-classifications. Hence, it is worthwhile to overview clinical manifestations and outcomes of overall TMA patients according to sub-classifications. We analyzed TMA patients whose serum lactate dehydrogenase levels >250 IU/L, with the presence of schistocytes in their peripheral blood smear, or with typical vascular pathologic abnormalities in their renal biopsy. We compared clinical manifestations including overall survival (OS) and renal survival according to TMA causes. A total of 117 TMA patients (57 primary and 60 secondary TMA) were analyzed. Renal symptom was the most common manifestation in whole patients, while renal function at diagnosis was worst in pregnancy-related TMA group. Primary TMA patients had more frequent CNS symptom and hematologic manifestation compared to secondary TMAs. Among secondary TMAs, pregnancy- and HSCT-related TMA patients showed prevalent hemolytic features. During 150.2 months of follow-up, 5-year OS rate was 64.8%. Poor prognostic factors included older age, combined hematologic and solid organ malignancies, lower hemoglobin levels, and lower serum albumin levels. There was no significant difference in OS between primary and secondary TMAs. Seventy-eight percent of patients experienced AKI during TMA. Five-year death-censored renal survival rate was poor with only 69.2%. However, excellent renal outcome was observed in pregnancy-associated TMA. TMA showed various clinical manifestations according to their etiology. Notably, both OS and renal survival were poor regardless of their etiologies except pregnancy-associated TMA. Physicians should differentiate a variety of TMA categories and properly manage this complex disease entity.

Circulating dsDNA, endothelial injury, and complement activation in thrombotic microangiopathy and GVHD

Transplant-associated thrombotic microangiopathy (TA-TMA) is a common and poorly recognized complication of hematopoietic stem cell transplantation (HSCT) associated with excessive complement activation, likely triggered by endothelial injury. An important missing piece is the link between endothelial injury and complement activation. We hypothesized that neutrophil extracellular traps (NETs) mechanistically link endothelial damage with complement activation and subsequent TA-TMA. Neutrophil activation releases granule proteins together with double-stranded DNA (dsDNA) to form extracellular fibers known as NETs. NETs have been shown to activate complement and can be assessed in humans by quantification of dsDNA in serum. We measured levels of dsDNA, as a surrogate for NETs in 103 consecutive pediatric allogeneic transplant recipients at day 0, +14, +30, +60, and +100. A spike in dsDNA production around day +14 during engraftment was associated with subsequent TA-TMA development. Peak dsDNA production around day +14 was associated with interleukin-8-driven neutrophil recovery. Increased dsDNA levels at days +30, +60, and +100 were also associated with increased mortality and gastrointestinal graft-versus-host disease (GVHD). NETs may serve as a mechanistic link between endothelial injury and complement activation. NET formation may be one mechanism contributing to the clinical overlap between GVHD and TA-TMA.

Use of the complement inhibitor Coversin to treat HSCT-associated TMA

Finding an inherited complement abnormality in HSCT-associated TMA provides a rationale for the use of a complement inhibitor.Alternative complement inhibitors such as Coversin should be considered in patients who are resistant to eculizumab.

Transplant-associated thrombotic microangiopathy is an endothelial complication associated with refractoriness of acute GvHD

There is increasing evidence that endothelial dysfunction is involved in refractoriness of acute GvHD (aGvHD). Here we investigated the hypothesis that another endothelial complication, transplant-associated thrombotic microangiopathy (TMA), contributes to the pathogenesis of aGvHD refractoriness. TMA was retrospectively assessed in 771 patients after allogeneic stem cell transplantation (alloSCT). Incidences of TMA and refractory aGvHD were correlated with biomarkers of endothelial damage obtained before alloSCT for patients receiving or not receiving statin-based endothelial prophylaxis (SEP). Diagnostic criteria for TMA and refractory aGvHD were met by 41 (5.3%) and 76 (10%) patients, respectively. TMA was overrepresented in patients with refractory aGvHD (45.0 vs 2.3% in all other patients, P<0.001). TMA independently increased mortality. Elevated pretransplant suppressor of tumorigenicity-2 and nitrates along with high-risk variants of the thrombomodulin gene were associated with increased risk of TMA. In contrast, SEP abolished the unfavorable outcome predicted by pretransplant biomarkers on TMA risk. Patients on SEP had a significantly lower risk of TMA (P=0.001) and refractory aGvHD (P=0.055) in a multivariate multistate model. Our data provide evidence that TMA contributes to the pathogenesis of aGvHD refractoriness. Patients with an increased TMA risk can be identified pretransplant and may benefit from pharmacological endothelium protection.

Hematopoietic stem cell transplantation and acute kidney injury in children: A comprehensive review

AKI in the setting of HSCT is commonly investigated among adult patients. In the same way, malignancies requiring treatment with HSCT are not limited to the adult patient population, AKI following HSCT is frequently encountered within pediatric patient populations. However, inadequate information regarding epidemiology and pathophysiology specific to pediatric patients prevents development of appropriate and successful therapeutic strategies for those afflicted. Addressing AKI in the context of sinusoidal obstruction syndrome, chemotherapy, thrombotic microangiopathy and hypertension post chemotherapy, glomerulonephritis, and graft versus host disease provides greater insight into renal impairment associated with these HSCT-related ailments. To obtain a better understanding of AKI among pediatric patients receiving HSCT, we investigated the current literature specifically addressing these areas of concern.

Diarrhea after allogeneic stem cell transplantation: beyond graft-versus-host disease

Diarrhea constitutes a frequent and often debilitating complication of allogeneic hematopoietic cell transplantation (alloHCT). Especially when accompanied by jaundice, skin rash, and symptoms of the upper gastrointestinal tract, diarrhea strongly suggests emergence of acute graft-versus-host disease (GvHD), which is a serious immune complication of the procedure, with possible fatal consequences. However, especially when diarrhea occurs as an isolated symptom, the other causes must be excluded before initiation of GvHD treatment with immune-suppressive drugs. In this article, a broad overview of the literature of different causes of diarrhea in the setting of alloHCT is provided, revealing causes and presentations different from those observed in the general population. We discuss gastrointestinal GvHD with a special focus on biomarkers, but also uncover underlying infectious: viral, bacterial, and parasitic as well as toxic causes of diarrhea. Finally, we suggest a practical algorithm of approach to patients with diarrhea after alloHCT, which may help to establish a proper diagnosis and initiate a causative treatment.

Diagnostic Utility of Complement Immunohistochemical Studies in Post-Stem Cell Transplant Intestinal Thrombotic Microangiopathy: Case Report

Thrombotic complications are a significant source of morbidity and mortality following hematopoietic stem cell transplants. Among them, transplant-associated thrombotic microangiopathy (TA-TMA) is a well-recognized syndrome that can affect various organ systems. Its etiology is related to endothelial injury accompanied by complement activation. As many of the signs and symptoms of the disease are also encountered in other complications following hematopoietic stem cell transplant, it can often be difficult to establish the diagnosis based on clinical data alone. Histopathologic examination of various tissues may be performed in difficult cases. However, the microscopic features of TA-TMA also overlap with those seen in other posttransplant complications, suggesting a need for additional tests to help in diagnosis. Here we describe a patient who presented with hemolytic anemia, thrombocytopenia, renal and neurological impairment, who also developed significant bloody diarrhea. Flexible sigmoidoscopy with biopsies was performed to determine the exact etiology of his gastrointestinal bleed. A diagnosis of intestinal TA-TMA was established with the use of immunohistochemical stains for complement components C5b-9 and C4d. This is the first report that highlights the utility of complement staining on histologic sections from digestive samples to render a definitive diagnosis of intestinal TA-TMA.

None of the above: thrombotic microangiopathy beyond TTP and HUS

Acquired thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are appropriately at the top of a clinician's differential when a patient presents with a clinical picture consistent with an acute thrombotic microangiopathy (TMA). However, there are several additional diagnoses that should be considered in patients presenting with an acute TMA, especially in patients with nondeficient ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity (>10%). An increased awareness of drug-induced TMA is also essential because the key to their diagnosis more often is an appropriately detailed medical history to inquire about potential exposures. Widespread inflammation and endothelial damage are central in the pathogenesis of the TMA, with the treatment directed at the underlying disease if possible. TMA presentations in the critically ill, drug-induced TMA, cancer-associated TMA, and hematopoietic transplant-associated TMA (TA-TMA) and their specific treatment, where applicable, will be discussed in this manuscript. A complete assessment of all the potential etiologies for the TMA findings including acquired TTP will allow for a more accurate diagnosis and prevent prolonged or inappropriate treatment with plasma exchange therapy when it is less likely to be successful.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice-Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh 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 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 Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

Transplant-associated thrombotic microangiopathy: opening Pandora's box

Transplant-associated thrombotic microangiopathy (TA-TMA) is an early complication of hematopoietic cell transplantation (HCT). A high mortality rate is documented in patients who are refractory to calcineurin inhibitor cessation. Estimates of TA-TMA prevalence vary significantly and are higher in allogeneic compared with autologous HCT. Furthermore, our understanding of the pathophysiology that is strongly related to diagnosis and treatment options is limited. Recent evidence has linked TA-TMA with atypical hemolytic uremic syndrome, a disease of excessive activation of the alternative pathway of complement, opening the Pandora's box in treatment options. As conventional treatment management is highly inefficient, detection of complement activation may allow for early recognition of patients who will benefit from complement inhibition. Preliminary clinical results showing successful eculizumab administration in children and adults with TA-TMA need to be carefully evaluated. Therefore, realizing the unmet needs of better understanding TA-TMA in this complex setting, we aimed to summarize current knowledge focusing on (1) critical evaluation of diagnostic criteria, (2) epidemiology and prognosis, (3) recent evidence of complement activation and endothelial damage and (4) treatment options.

Syndromes of Thrombotic Microangiopathy

Thrombotic thrombocytopenia purpura (TTP) and the hemolytic uremic syndrome (HUS) are rare thrombotic microangiopathies that can be rapidly fatal. Although the acquired versions of TTP and HUS are generally highest on this broad differential, multiple rarer entities can produce a clinical picture similar to TTP/HUS, including microangiopathic hemolysis, renal failure, and neurologic compromise. More recent analysis has discovered a host of genetic factors that can produce microangiopathic hemolytic syndromes. This article discusses the current understanding of thrombotic microangiopathy and outlines the pathophysiology and causative agents associated with each distinct syndrome as well as the most accepted treatments.

Transplantation-associated thrombotic microangiopathy isolated to a congenital anomaly of the lung

TA-TMA is a post-hematopoietic stem cell transplant complication with clinical features of hemolytic anemia and thrombocytopenia. A 26-month-old child who had had an allogeneic transplant for treatment of DBA developed severe TA-TMA with heavy red blood cell and platelet transfusion dependence. Incidentally, he was found to have a lung sequestration. TA-TMA resolved and transfusion dependence resolved after resection of the sequestration. The finding suggests the malformation vasculature was selectively vulnerable to the trigger of TA-TMA-raising perhaps a clue to basic pathophysiology of TA-TMA and/or vascular malformations.

Neurologic Complications after Allogeneic Hematopoietic Stem Cell Transplantation

Neurologic complications after hematopoietic stem cell transplantation are frequently life-threatening, and their clinical management can be highly challenging. A wide spectrum of causative factors-including drug-related toxicities; infections sustained by virus, bacteria, or invasive molds; metabolic encephalopathy; cerebrovascular disorders; immune-mediated disorders; and disease recurrence-may lead to potentially lethal complications. Moreover, given that some neurologic complications are not uncommonly diagnosed post mortem, their overall incidence is likely to be underestimated. Their prompt recognition and timely treatment are of paramount importance to reduce the risk for transplantation-related death.

Is complement blockade an acceptable therapeutic strategy for hematopoietic cell transplant-associated thrombotic microangiopathy?

Diagnosis and management of hematopoietic cell transplant-associated thrombotic microangiopathy (TA-TMA) are very complex and controversial, given multiple ongoing issues and comorbidities in sick transplant recipients. Complement activation via classic and alternative pathways is emerging as a potential pathogenetic mechanism in the development of TA-TMA. Complement-centric diagnostic strategy using functional and genetic tests may possibly support diagnosis, enhance molecular understanding and direct drug development. Complement blockade using eculizumab has shown some promising rates of hematologic responses, however, survival may still be poor. Early discontinuation of calcineurin inhibitor where feasible, use of eculizumab, aggressive infection prophylaxis, close monitoring and early treatment of potential complications including GvHD and organ failure may improve outcomes. A number of complement inhibitors are in the development and may change treatment paradigm. Future studies are important to better understand TA-TMA as a disease process and may aim to confirm the role of complement activation in TA-TMA, enhance diagnostic strategy, determine therapeutic approaches and strategies to reduce the risk of other complications particularly infection and GvHD.

Hematopoietic cell transplantation-associated thrombotic microangiopathy: a review of pathophysiology, diagnosis, and treatment

Transplant-associated thrombotic microangiopathy (TA-TMA) is a multifactorial disorder caused by systemic vascular endothelial injury that can be triggered by several mechanisms during the transplant process. Thrombotic microangiopathy may affect multiple systems and occurs in ~30% of patients undergoing hematopoietic stem cell transplantation. A subgroup of patients with thrombotic microangiopathy develop TA-TMA, and the other may develop other thrombotic microangiopathic disorders such as thrombotic thrombocytopenic purpura, a condition with similar finding but different pathophysiology involving ADAMTS-13. The mortality rates in patients who develop severe TA-TMA are in excess of 80%. Recent investigations show that complement system activation in patients with TA-TMA is a very poor prognostic sign and implicates complement dysregulation as a key pathway in the pathogenesis of TA-TMA and its disease phenotype. The original diagnostic criteria for TA-TMA included hematologic and renal injury markers, which are limited in their ability to detect only advanced disease, and therefore may result in delayed TA-TMA diagnosis in transplant patients. A recent set of diagnostic criteria added markers of complement activation, proteinuria, and hypertension, with predicted improved detection of early TA-TMA. Supportive care that includes elimination of potentially toxic agents such as calcineurin inhibitors and sirolimus, adequate antimicrobial treatment, and maintaining adequate renal functions using renal replacement therapy may be sufficient for treatment of mild-to-moderate TA-TMA. Plasma exchange, which is a potentially curative therapy in thrombotic thrombocytopenic purpura, has no proven efficacy in TA-TMA. Blocking the complement system with eculizumab is currently the most effective treatment to circumvent the poor outcome in patients with severe TA-TMA.

Antineoplastic Treatment and Renal Injury: An Update on Renal Pathology Due to Cytotoxic and Targeted Therapies

Cancer patients experience kidney injury from multiple sources, including the tumor itself, diagnostic procedures, hypovolemia, infection, and drug exposure, superimposed upon baseline chronic damage. This review will focus on cytotoxic or targeted chemotherapy-associated renal injury. In this setting, tubulointerstitial injury and thrombotic microangiopathy (vascular injury) are more common than other forms of kidney injury including glomerular. Cisplatin, pemetrexed, and ifosfamide are well-known causes of acute tubular injury/necrosis. Acute interstitial nephritis seems underrecognized in this clinical setting. Interstitial nephritis is emerging as an "immune-related adverse effect" (irAE's) with immune checkpoint inhibitors in small numbers of patients. Acute kidney injury is rarely reported with targeted therapies such as BRAF inhibitors (vemurafinib, dabrafenib), ALK inhibitors (crizotinib), and mTOR inhibitors (everolimus, temsirolimus), but additional biopsy data are needed. Tyrosine kinase inhibitors and monoclonal antibodies that block the vascular endothelial growth factor pathway are most commonly associated with thrombotic microangiopathy. Other causes of thrombotic microangiopathy in the cancer patients include cytotoxic chemotherapies such as gemcitabine and mitomycin C, hematopoietic stem cell transplant, and cancer itself (usually high-stage adenocarcinoma with marrow and vascular invasion). Cancer patients are historically underbiopsied, but biopsy can reveal type, acuity, and chronicity of renal injury, and facilitate decisions concerning continuation of chemotherapy and/or initiation of renoprotective therapy. Biopsy may also reveal unrelated and unanticipated findings in need of treatment.