From humoral rejection to generalized thrombotic microangiopathy--role of acquired ADAMTS13 deficiency in a renal allograft recipient

Unveiling the Incidence and Graft Survival Rate in Kidney Transplant Recipients With De Novo Thrombotic Microangiopathy: A Systematic Review and Meta-Analysis

De novo thrombotic microangiopathy (TMA) is a rare and challenging condition in kidney transplant recipients, with limited research on its incidence and impact on graft survival. This study conducted a systematic review and meta-analysis of 28 cohorts/single-arm studies and 46 case series/reports from database inception to June 2022. In meta-analysis, among 14,410 kidney allograft recipients, de novo TMA occurred in 3.20% [95% confidence interval (CI): 1.93-4.77], with systemic and renal-limited TMA rates of 1.38% (95% CI: 06.5-2.39) and 2.80% (95% CI: 1.27-4.91), respectively. The overall graft loss rate of de novo TMA was 33.79% (95% CI: 26.14-41.88) in meta-analysis. This study provides valuable insights into the incidence and graft outcomes of de novo TMA in kidney transplant recipients.

Thrombotic microangiopathy after renal transplantation: Current insights in de novo and recurrent disease

Thrombotic microangiopathy (TMA) is one of the most devastating sequalae of kidney transplantation. A number of published articles have covered either de novo or recurrent TMA in an isolated manner. We have, hereby, in this article endeavored to address both types of TMA in a comparative mode. We appreciate that de novo TMA is more common and its prognosis is poorer than recurrent TMA; the latter has a genetic background, with mutations that impact disease behavior and, consequently, allograft and patient survival. Post-transplant TMA can occur as a recurrence of the disease involving the native kidney or as de novo disease with no evidence of previous involvement before transplant. While atypical hemolytic uremic syndrome is a rare disease that results from complement dysregulation with alternative pathway overactivity, de novo TMA is a heterogenous set of various etiologies and constitutes the vast majority of post-transplant TMA cases. Management of both diseases varies from simple maneuvers, e.g., plasmapheresis, drug withdrawal or dose modification, to lifelong complement blockade, which is rather costly. Careful donor selection and proper recipient preparation, including complete genetic screening, would be a pragmatic approach. Novel therapies, e.g., purified products of the deficient genes, though promising in theory, are not yet of proven value.

De novo thrombotic microangiopathy after kidney transplantation

Thrombotic microangiopathy (TMA) is a serious complication of transplantation that adversely affects kidney transplant recipient and allograft survival. Post-transplant TMA is usually classified into two categories: 1) recurrent TMA and 2) de novo TMA. Atypical hemolytic uremic syndrome (aHUS) resulting from dysregulation and over-activation of the alternate complement pathway is a rare disease but the most common diagnosis associated with recurrence in the allografts. De novo TMA, on the other hand, represents an overwhelming majority of the cases of post-transplant TMA and is a substantially more heterogeneous entity than recurrent aHUS. Here, we review the etio-pathogenesis, diagnosis and treatment options for de novo post-transplant TMA. It is usually in the setting of calcineurin inhibitor use, mammalian target of rapamycin inhibitor use, or antibody mediated rejection; recently genetic mutations in complement regulatory genes for Factor H and Factor I similar to those described in aHUS have been reported in up to a third of these patients. Systemic signs of TMA are frequently absent, and a renal allograft biopsy is often needed to establish the diagnosis. Although withdrawal of the offending agents is usually the first line of treatment and resolution of laboratory abnormalities has been documented with this approach in several case reports and case series, available retrospective data demonstrate lack of benefit in long-term graft outcomes. Co-stimulation blockage with belatacept provides an effective alternate immunosuppressive strategy for these patients. Anti-complement therapy with eculizumab is effective in some cases; further work is required to define which patients with TMA (with and without concomitant antibody-mediated rejection) would benefit from receiving this treatment, and what biomarkers can be used to identify them.

Antiphospholipid syndrome in renal transplantation

Antiphospholipid syndrome (APS) may occur in isolation or in association with systemic lupus erythematosus (SLE), with the potential to cause renal failure via several distinct pathologies. Renal transplantation in the presence of APS carries a risk of early graft loss from arterial or venous thrombosis, or thrombotic microangiopathy (TMA). Whilst perioperative anticoagulation reduces the risk of large vessel thrombosis, it may result in significant haemorrhage, and its efficacy in preventing post-transplant TMA is uncertain. Here, we report a patient with end-stage kidney disease (ESKD) due to lupus nephritis and APS, in whom allograft TMA developed soon after transplantation despite partial anticoagulation. TMA resolved with plasma exchange-based therapy albeit with some irreversible graft damage and renal impairment. We discuss the differential diagnosis of post-transplant TMA, and current treatment options.

Children and adults with thrombotic thrombocytopenic purpura associated with severe, acquired Adamts13 deficiency: comparison of incidence, demographic and clinical features

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) associated with severe, acquired ADAMTS13 deficiency is uncommonly reported in children. The incidence, demographic, and clinical features of these children, compared to adults, have not been described.

PROCEDURES

This study focused on children (<18 years old) and adults with TTP associated with severe, acquired ADAMTS13 deficiency, defined as activity <10%. The incidence rates for TTP in children and adults were calculated from patients enrolled in the Oklahoma TTP-HUS (Hemolytic-Uremic syndrome) Registry, 1996-2012. To describe demographic and clinical features, children with TTP were also identified from a systematic review of published reports and from samples sent to a reference laboratory for analysis of ADAMTS13.

RESULTS

The standardized annual incidence rate of TTP in children was 0.09 × 10(6) children per year, 3% of the incidence rate among adults (2.88 × 10(6) adults per year). Among the 79 children who were identified (one from the Oklahoma Registry, 55 from published reports, 23 from the reference laboratory), TTP appeared to be more common among females, similar to the relative increased frequency of women among adults with TTP, and more common in older children. Clinical data were available on 52 children; the frequency of severe renal failure, relapse, treatment with rituximab, and systemic lupus erythematosus in these children was similar to adults with TTP.

CONCLUSIONS

TTP associated with severe, acquired ADAMTS13 deficiency is uncommon in children. The demographic and clinical features of these children are similar to the features of adults with TTP.

Complement genes strongly predict recurrence and graft outcome in adult renal transplant recipients with atypical hemolytic and uremic syndrome

Atypical hemolytic and uremic syndrome (aHUS) is a severe disease strongly associated with genetic abnormalities in the complement alternative pathway. In renal posttransplantation, few data are available on recurrence risk and graft outcome according to genetic background in aHUS patients. The aim of this study was to identify risk factors for recurrence and transplant outcome and, in particular, the role of complement gene abnormalities. We retrospectively studied 57 aHUS patients who had received 71 renal transplants. A mutation in complement gene was identified in 39 (68%), in factor H (CFH), factor I (CFI), membrane cofactor-protein (MCP), C3 and factor B (CFB). At 5 years, death-censored graft survival was 51%. Disease recurrence was associated with graft loss (p = 0.001). Mutations in complement genes were associated with higher risk of recurrence (p = 0.009). Patients with CFH or gain of function (C3, CFB) mutations had a highest risk of recurrence. M-TOR inhibitor was associated with significant risk of recurrence (p = 0.043) but not calcineurin inhibitor immunosuppressive treatment (p = 0.29). Preemptive plasmatherapy was associated with a trend to decrease recurrence (p = 0.07). Our study highlights that characterization of complement genetic abnormalities predicts the risk of recurrence-related graft loss and paves the way for future genetically based individualized prophylactic therapeutic strategies.

Eculizumab for the treatment of de novo thrombotic microangiopathy post simultaneous pancreas-kidney transplantation--a case report

A 34-year-old female recipient of a simultaneous pancreas-kidney transplant presented 7 days posttransplant with acute renal allograft dysfunction, thrombocytopenia, and microangiopathic hemolytic anemia. Renal biopsy revealed acute antibody-mediated rejection (AMR) and acute thrombotic microangiopathy (TMA). Clinical and laboratory manifestations, which had only partly responded to treatment with daily plasma exchange and intravenous immunoglobulin, resolved rapidly and completely to eculizumab (Soliris, Alexion Pharmaceuticals, Inc., Cheshire, Conn), a complement factor C5 antibody. De novo posttransplant TMA is a rare and serious complication that can lead to graft loss in up to one third of cases. This is the first report of successful treatment of de novo TMA with eculizumab, which has previously shown benefit in recurrent atypical hemolytic uremic syndrome as well as in refractory acute AMR. Targeted complement inhibition offers the promise of a safe and effective therapeutic strategy in de novo TMA, especially in light of recent evidence suggesting that genetic mutations in complement regulatory proteins may predispose transplant recipients to this serious disease.

Thrombotic microangiopathy-like disorder after living-donor liver transplantation: A single-center experience in Japan

AIM: To investigate thrombotic microangiopathy (TMA) in liver transplantion, because TMA is an infrequent but life-threatening complication in the transplantation field.

METHODS: A total of 206 patients who underwent living-donor liver transplantation (LDLT) were evaluated, and the TMA-like disorder (TMALD) occurred in seven recipients.

RESULTS: These TMALD recipients showed poor outcomes in comparison with other 199 recipients. Although two TMALD recipients successfully recovered, the other five recipients finally died despite intensive treatments including repeated plasma exchange (PE) and re-transplantation. Histopathological analysis of liver biopsies after LDLT revealed obvious differences according to the outcomes. Qualitative analysis of antibodies against a disintegrin-like domain and metalloproteinase with thrombospondin type 1 motifs (ADAMTS-13) were negative in all patients. The fragmentation of red cells, the microhemorrhagic macules and the platelet counts were early markers for the suspicion of TMALD after LDLT. Although the absolute values of von Willebrand factor (vWF) and ADAMTS-13 did not necessarily reflect TMALD, the vWF/ADAMTS-13 ratio had a clear diagnostic value in all cases. The establishment of adequate treatments for TMALD, such as PE for ADAMTS-13 replenishment or treatments against inhibitory antibodies, must be decided according to each case.

CONCLUSION: The optimal induction of adequate therapies based on early recognition of TMALD by the reliable markers may confer a large advantage for TMALD after LDLT.

Complement mutation-associated de novo thrombotic microangiopathy following kidney transplantation

Mutations in one or more genes encoding complement-regulatory proteins predispose to atypical hemolytic uremic syndrome (aHUS) and its recurrence following kidney transplantation. We evaluated plasma complement level and performed a screening for mutations in genes encoding complement Factors H and I (CFH, CFI) and membrane cofactor protein (MCP) in 24 kidney transplant recipients experiencing de novo thrombotic microangiopathy (TMA). Six patients presented with low C3 and/or low Factor B levels suggestive complement alternative pathway. A mutation in the CFH or CFI gene was found in 7/24 patients (29%), two of whom had a mutation in both genes. On the contrary, no mutation was identified in a control kidney transplant patients group (n = 25) without TMA. Patients with or without mutations were similar with regard to clinical features. Eight out of 24 patients lost their graft within 1 year of posttransplantation including six patients with a CFH mutation or a decrease of C3 or CFB in plasma. To conclude, kidney transplant patients with de novo TMA exhibit an unexpectedly high frequency of CFH and CFI mutations. These results suggest that genetic abnormalities may represent risk factors for de novo TMA after kidney transplantation and raise the question of the best therapeutic strategy.

Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura

Discoveries during the past decade have revolutionized our understanding of idiopathic thrombotic thrombocytopenic purpura (TTP). Most cases in adults are caused by acquired autoantibodies that inhibit ADAMTS13, a metalloprotease that cleaves von Willebrand factor within nascent platelet-rich thrombi to prevent hemolysis, thrombocytopenia, and tissue infarction. Although approximately 80% of patients respond to plasma exchange, which removes autoantibody and replenishes ADAMTS13, one third to one half of survivors develop refractory or relapsing disease. Intensive immunosuppressive therapy with rituximab appears to be effective as salvage therapy, and ongoing clinical trials should determine whether adjuvant rituximab with plasma exchange also is beneficial at first diagnosis. A major unanswered question is whether plasma exchange is effective for the subset of patients with idiopathic TTP who do not have severe ADAMTS13 deficiency.

Enhanced allograft survival and modulation of T-cell alloreactivity induced by inhibition of MMP/ADAM enzymatic activity

Recent studies have shown significantly increased expression of matrix metalloproteinases (MMP) and disintegrin-type metalloproteinases (ADAM) during allograft rejection. In this regard, our previous studies have demonstrated contrasting roles for MMP-2 and MMP-9 during allograft rejection: MMP-2-deficiency enhanced allograft survival while MMP-9-deficiency decreased allograft survival. The aim of this study was to determine the effect of broad-spectrum MMP/ADAM inhibition on the pathogenesis of allograft rejection. Toward this, heterotopic BALB/c cardiac allografts were transplanted into C57BL/6 recipients treated with MMP/ADAM inhibitors, GM6001 or doxycycline. Systemic MMP/ADAM inhibition significantly enhanced allograft survival. Functioning allografts recovered from MMP/ADAM inhibitor-treated recipients showed lower cellular infiltration and tissue remodeling than rejected allografts recovered from control recipients. In addition, decreased chemotaxis of CD4+ and CD8+ T cells, B cells and macrophages was observed in vitro in the presence of MMP/ADAM inhibitors. Enhanced T-cell alloreactivity was also observed ex vivo in MMP/ADAM inhibitor-treated recipients and in vitro in the presence of MMP/ADAM inhibitors. These observations were associated with enhanced cytokine, chemokine and growth factor production. These results indicate that MMPs and ADAMs play a critical role in the pathogenesis of allograft rejection and may represent novel therapeutic targets for the treatment and/or prevention of this disease.