Efficacy of Eculizumab Therapy for Atypical Hemolytic Uremic Syndrome Recurrence and Antibody-Mediated Rejection Progress After Renal Transplantation With Preformed Donor-Specific Antibodies: Case Report

Successful Reversal of Refractory Posttransplant Thrombotic Microangiopathy with Eculizumab

Posttransplant thrombotic microangiopathy (PT-TMA) can be caused by calcineurin inhibitors (CNIs), ischemic injury, infections, or antibody-mediated rejection (ABMR). Delayed recognition can result in allograft loss. We describe the first reported case of successful reversal of refractory PT-TMA with eculizumab in India. It highlights the importance of prompt diagnosis and benefit from an early initiation of eculizumab therapy in refractory cases.

Drug-induced de novo thrombotic microangiopathy diagnosed 2 years after renal transplantation: a case report and literature review

Background

Post-transplant de novo thrombotic microangiopathy (TMA) is a rare yet serious complication that generally can develop in renal transplant recipients immediately after reperfusion or several months after transplantation. Here, we report a case of systemic tacrolimus-associated TMA in a patient diagnosed 2 years after renal transplantation.

Case presentation

A 49-year-old woman presented with severe anemia 18 months after undergoing renal transplantation. Anemia was refractory to recombinant human erythropoietin and was suspected to be due to excessive menstruation. Anemia persisted even after hysterectomy, and thereafter, pancytopenia developed. A bone marrow biopsy was performed and showed no evidence of myeloproliferative neoplasms. Furthermore, an increase in serum lactate dehydrogenase level and the appearance of schistocytes on peripheral blood smear was noted 24 months post-transplant. Other possible causes of de novo TMA were excluded, and an allograft biopsy was performed. Pathological findings of the allograft biopsy showed that some afferent arterioles had formed thrombi. Suspecting tacrolimus to be the cause of TMA, 25 months after the transplant, we switched treatment to cyclosporine. Pancytopenia and renal function improved after switching to this calcineurin inhibitor. Subsequently, her allograft renal function stabilized for three years after renal transplantation.

Conclusion

We encountered a case of secondary drug-induced TMA in the late stages of renal transplantation. Therefore, TMA should be suspected when anemia with hemolysis is observed in recipients of kidney transplant.

The complement system in pediatric acute kidney injury

The complement cascade is an important part of the innate immune system. In addition to helping the body to eliminate pathogens, however, complement activation also contributes to the pathogenesis of a wide range of kidney diseases. Recent work has revealed that uncontrolled complement activation is the key driver of several rare kidney diseases in children, including atypical hemolytic uremic syndrome and C3 glomerulopathy. In addition, a growing body of literature has implicated complement in the pathogenesis of more common kidney diseases, including acute kidney injury (AKI). Complement-targeted therapeutics are in use for a variety of diseases, and an increasing number of therapeutic agents are under development. With the implication of complement in the pathogenesis of AKI, complement-targeted therapeutics could be trialed to prevent or treat this condition. In this review, we discuss the evidence that the complement system is activated in pediatric patients with AKI, and we review the role of complement proteins as biomarkers and therapeutic targets in patients with AKI.

Complement Activation Fragments Are Increased in Critically Ill Pediatric Patients with Severe AKI

Background

Children who are critically ill with AKI suffer from high morbidity and mortality rates, and lack treatment options. Emerging evidence implicates the role of complement activation in AKI pathogenesis, which could potentially be treated with complement inhibitors. The purpose of this study is to evaluate the association between complement activation fragments and severity of AKI in children who are critically ill.

Methods

A biorepository of samples from children who are critically ill from a prior multisite study was leveraged to identify children with stage 3 AKI and matched to patients without AKI on the basis of PELOD-2 (illness severity) scores. Specimens were analyzed for plasma and urine complement activation fragments of factor B, C3a, C4a, and sC5b-9. The primary outcomes were MAKE30 and severe AKI rates.

Results

In total, 14 patients with stage 3 AKI (five requiring RRT) were matched to 14 patients without AKI. Urine factor Ba and plasma C4a levels increased stepwise as severity of AKI increased, from no AKI to stage 3 AKI, to stage 3 AKI with RRT need. Plasma C4a levels were independently associated with increased risk of MAKE30 outcomes (OR, 3.2; IQR, 1.1-8.9), and urine Ba (OR, 1.9; IQR, 1.1-3.1), plasma Bb (OR, 2.7; IQR, 1.1-6.8), C4a (OR, 13.0; IQR, 1.6-106.6), and C3a (OR, 3.3; IQR, 1.3-8.4) were independently associated with risk of severe stage 2-3 AKI on day 3 of admission.

Conclusions

Multiple complement fragments increase as magnitude of AKI severity increases. Very high levels of urine Ba or plasma C4a may identify patients at risk for severe AKI, hemodialysis, and MAKE30 outcomes. The fragments may be useful as a functional biomarker of complement activation and may identify those patients to study complement inhibition to treat or prevent AKI in children who are critically ill. These findings suggest the need for further specific investigations of the role of complement activation in children who are critically ill and at risk of AKI.

Use of Eculizumab in Transplant-Associated Thrombotic Microangiopathy in a Patient With Polycystic Kidney Disease Immediately Post-Kidney Transplant: A Case Report

Transplant-associated thrombotic microangiopathy (TMA) in the post-organ transplantation setting occurs from a number of potential inciting factors, such as the use of calcineurin inhibitors, ischemic injury, infections, or antibody-mediated rejection leading to unchecked complement activation and end-organ damage. Delayed recognition of this condition can result in allograft loss. In this case description, we describe the first case of de novo TMA in a patient with polycystic kidney disease that occurred immediately after kidney transplantation. The diagnosis was made promptly on the basis of clinical and laboratory characteristics by a multidisciplinary team and confirmed through kidney biopsy, which showed acute TMA. The patient was successfully managed by replacing tacrolimus with belatacept, which targets cytotoxic T lymphocyte antigen 4, and use of eculizumab, a C5 inhibitor. Eculizumab treatment was discontinued after 3 months of complement inhibition on the patient's request, and relapse of TMA has not been encountered after more than 1 year of follow-up.

Mechanisms and clinical applications of immunosuppressive medications

Immunosuppressive medications and regimens have evolved with significant advancements in the understanding of the immunologic process after solid organ transplantation. Medications can block the communication between antigen-presenting cells and T-cells, the activation and proliferation of T-cells, antibody production by plasma cells, and the activation of the complement system by antibodies. T-cell depleting antibodies and interleukin-2 receptor blockers are commonly used during induction therapy. Calcineurin inhibitors, antimetabolites, antiproliferative agents, and corticosteroids are commonly used in maintenance therapy regimens. These medications decrease the rates of rejection episodes and markedly increase the survival rates of short-term grafts. However, in terms of the survival rate of long-term grafts, there is still room for improvement. Opportunistic infections, development of cancer, metabolic diseases, and calcineurin inhibitor toxicity are hurdles in the improvement in survival rates of long-term grafts. Therefore, many efforts are being taken to overcome these hurdles, such as the development of new drugs, individualization of immunosuppression, and induction of immune tolerance.

Eculizumab in atypical hemolytic uremic syndrome: strategies toward restrictive use

With the introduction of the complement C5-inhibitor eculizumab, a new era was entered for patients with atypical hemolytic uremic syndrome (aHUS). Eculizumab therapy very effectively reversed thrombotic microangiopathy and reduced mortality and morbidity. Initial guidelines suggested lifelong treatment and recommended prophylactic use of eculizumab in aHUS patients receiving a kidney transplant. However, there is little evidence to support lifelong therapy or prophylactic treatment in kidney transplant recipients. Worldwide, there is an ongoing debate regarding the optimal dose and duration of treatment, particularly in view of the high costs and potential side effects of eculizumab. An increasing but still limited number of case reports and small cohort studies suggest that a restrictive treatment regimen is feasible. We review the current literature and focus on the safety and efficacy of restrictive use of eculizumab. Our current treatment protocol is based on restrictive use of eculizumab. Prospective monitoring will provide more definite proof of the feasibility of such restrictive treatment.