Post-transplant hemolytic-uremic syndrome

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.

Characteristics, management and outcomes of atypical haemolytic uraemic syndrome in kidney transplant patients: a retrospective national study

Background

Kidney transplantation (KTx) is a strong trigger for the development of either recurrent or de novo atypical haemolytic uraemic syndrome (aHUS). According to previous studies, eculizumab (ECU) is effective for prophylaxis and for treatment of recurrence.

Methods

We evaluated the experiences of Spanish patients with recurrent and de novo aHUS associated with KTx, treated or not treated with ECU. In the de novo group, we classified patients as having early de novo (during the first month) or late de novo aHUS (subsequent onset).

Results

We analysed 36 cases of aHUS associated with KTx. All of the 14 patients with pre-KTx diagnosis of aHUS were considered to have high or moderate risk of recurrence. Despite receiving grafts from suboptimal donors, prophylactic ECU was effective for avoiding recurrence. The drug was stopped only in two cases with low–moderate risk of recurrence and was maintained in high-risk patients with no single relapse. There were 22 de novo aHUS cases and 16 belonged to the early de novo group. The median time of onset in the late group was 3.4 years. The early group had a better response to ECU than the late group, probably due to earlier diagnosis and use of the drug. No genetic pathogenic variant was detected in de novo aHUS cases, suggesting a secondary profile of the disease. ECU was stopped in all de novo patients with no relapses. ECU was well tolerated in all cases.

Conclusions

Both groups (pre-aHUS and de novo) presented different clinical profiles, management approaches and outcomes. One should consider aHUS regardless of time after KTx. Genetic studies are crucial to stratify risks of relapse and to determine necessary lengths of treatment. We suggest short ECU treatment for de novo cases without pathogenic mutation and that ECU treatment be considered pre-emptively for patients with moderate or high risk of recurrence.

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.

Shigella sonnei and hemolytic uremic syndrome: A case report and literature review

Hemolytic uremic syndrome (HUS) is a well-described process that is known to cause severe renal dysfunction, thrombocytopenia, and anemia. HUS is typically associated with toxins (shiga-like and shigella toxin) found in strains of E. coli and Shigella spp [1], [2], [3]. We present a case of a 27 year-old man with jaundice, thrombocytopenia, and renal dysfunction who was found to have HUS in the setting of Shigella sonnei infection. Outside of developing countries, cases of HUS related to S. sonnei are largely unreported.

Complement related kidney diseases: Recurrence after transplantation

The recurrence of renal disease after renal transplantation is becoming one of the main causes of graft loss after kidney transplantation. This principally concerns some of the original diseases as the atypical hemolytic uremic syndrome (HUS), the membranoproliferative glomerulonephritis (MPGN), in particular the MPGN now called C3 glomerulopathy. Both this groups of renal diseases are characterized by congenital (genetic) or acquired (auto-antibodies) modifications of the alternative pathway of complement. These abnormalities often remain after transplantation because they are constitutional and poorly influenced by the immunosuppression. This fact justifies the high recurrence rate of these diseases. Early diagnosis of recurrence is essential for an optimal therapeutically approach, whenever possible. Patients affected by end stage renal disease due to C3 glomerulopathies or to atypical HUS, may be transplanted with extreme caution. Living donor donation from relatives is not recommended because members of the same family may be affected by the same gene mutation. Different therapeutically approaches have been attempted either for recurrence prevention and treatment. The most promising approach is represented by complement inhibitors. Eculizumab, a monoclonal antibody against C5 convertase is the most promising drug, even if to date is not known how long the therapy should be continued and which are the best dosing. These facts face the high costs of the treatment. Eculizumab resistant patients have been described. They could benefit by a C3 convertase inhibitor, but this class of drugs is by now the object of randomized controlled trials.

Advances and challenges in the management of complement-mediated thrombotic microangiopathies

Complement activation plays a major role in several renal pathophysiological conditions. The three pathways of complement lead to C3 activation, followed by the formation of the anaphylatoxin C5a and the terminal membrane attack complex (MAC) in blood and at complement activating surfaces, lead to a cascade of events responsible for inflammation and for the induction of cell lysis. In case of ongoing uncontrolled complement activation, endothelial cells activation takes place, leading to events in which at the end thrombotic microangiopathy can occur. Atypical haemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy characterized by excessive complement activation on the surface of the microcirculation. It is a severe, rare disease which leads to end-stage renal failure (ESRF) and/or to death in more than 50% of patients without treatment. In the first decade of the second millennium, huge progress in understanding the aetiology of this disease was made, which paved the way to better treatment. First, protocols of plasma therapy for treatment, prevention of relapses and for renal transplantation in those patients were set up. Secondly, in some severe cases, combined kidney and liver transplantation was reported. Finally, at the end of this decade, the era of complement inhibitors, as anti-C5 monoclonal antibody (anti-C5 mAb) began. The past five years have seen growing evidence of the favourable effect of anti-C5 mAb in aHUS which has made this drug the first-line treatment in this disease. The possible complication of meningococcal infection needs appropriate vaccination before its use. Unfortunately, the worldwide use of anti-C5 mAb is limited by its very high price. In the future, extension of indications for anti-C5 mAb use, the elaboration of generics and of mAbs directed towards other complement factors of the terminal pathway of the complement system might succeed in reducing the cost of this new valuable therapeutic approach and render it available worldwide for patients from all social classes.

Renal dysfunction in end-stage liver disease and post-liver transplant

Renal dysfunction is a frequent complication in patients with end-stage liver disease awaiting orthotopic liver transplantation and in the post-liver transplant period. Although the stereotypical form of renal dysfunction is the hepatorenal syndrome, other causes of acute kidney injury in this population include prerenal azotemia and acute tubular necrosis. Renal injury in a patient with cirrhosis is associated with a poor prognosis.

Successful conversion to belatacept after thrombotic microangiopathy in kidney transplant patients

Thrombotic microangiopathy (TMA) is a severe complication of kidney transplantation. TMA may occur de novo or as recurrent disease post-transplant. De novo disease is usually associated with immunosuppressive drugs or can be seen as a part of endothelial damage that accompanies antibody-mediated rejection. Treatment for de novo TMA is limited to plasma exchange and change in immunosuppression. We report two cases of de novo TMA post-transplant that were successfully treated by converting to belatacept for maintenance immunosuppression.

Thrombotic microangiopathy in renal allografts

Thrombotic microangiopathy (TMA) is a serious complication of renal transplantation. It is a morphological expression of various etiological factors. In a renal allograft, TMA can occur de novo or be a recurrent disease. The aim of this study was to analyze the etiological factors and observe the changing trends of TMA with respect to emerging new etiological factors. We evaluated 131 graft biopsies over a period of 2½ years (2010-2012). All the renal biopsies were formalin fixed, paraffin embedded. Twenty serial sections were studied. Stains routinely used were Hematoxylin and Eosin, Periodic Acid Schiff, Massons Trichrome and Silver Methenamine stains. C4d by immunohistochemical method was done on all graft biopsies. Incidence of TMA in our series was 9.1%. Out of the 12 cases, five were associated with calcineurin inhibitor toxicity, three were diagnosed as acute antibody-mediated rejection, and two were recurrent haemolytic uremic syndrome. One patient developed haemolytic uremic syndrome on treatment with sirolimus and one patient was cytomegalovirus positive on treatment with ganciclovir, developed haemolytic uremic syndrome during treatment course. This study describes a spectrum of etiological factors for thrombotic mciroangiopathy ranging from common cause like calcineurin inhibitor toxicity to rare cause like ganciclovir induced TMA.

Targeted strategies in the prevention and management of atypical HUS recurrence after kidney transplantation

Atypical hemolytic and uremic syndrome (aHUS) is associated with a high rate of recurrence and poor outcomes after kidney transplantation. Fortunately, recent advances in the understanding of the pathogenesis of aHUS have permitted an individualized risk assessment of post-transplant recurrence. Acquired or inherited dysregulation of the alternative complement pathway, thought to be the driving force of the disease, is identified in most aHUS patients. Notably, depending on the mutations involved, the risk of recurrence greatly varies, highlighting the importance of undertaking etiological investigations prior to kidney transplantation. In those with moderate to high risk of recurrence, the use of a prophylactic therapy, consisting in either plasmapheresis or eculizumab therapies, represents a major stride forward in the prevention of aHUS recurrence after kidney transplantation. In those who experience aHUS recurrence, a growing number of observations suggest that eculizumab therapy outperforms curative plasma therapy. The optimal duration of both prophylactic and curative therapies remains an important, yet unaddressed, issue. In this respect, the kidney transplant recipients, continuously exposed to endothelial-insulting factors, referred here as to triggers, might have a sustained high risk of recurrence. A global therapeutic approach should thus attempt to reduce exposure to these triggers.

Multifaceted hemolytic uremic syndrome in pediatrics

Hemolytic uremic syndromes can have devastating consequences in childhood. The common feature of a microangiopathic hemolytic anemia and thrombocytopenia associated with varying degrees of renal injury often creates diagnostic confusion. The inability to arrive at a definitive diagnosis quickly can lead to a delay in initiating renal-preserving and sometimes life-saving treatment. Currently, both the treatment plan and the prognosis vary substantially according to the presumed diagnosis. The availability of anti-complement therapy makes differentiating the cause of the hemolytic uremic syndrome particularly critical. Therefore, it is imperative that consideration be given to each of the possible syndromes at presentation in order to facilitate correct diagnosis and development of an appropriate treatment strategy for both the acute phase and for the long-term care of the patient.

Management of renal dysfunction in patients receiving a liver transplant

Renal dysfunction is a frequent complication in patients with endstage liver disease awaiting orthotopic liver transplantation. Although the stereotypical form of renal dysfunction is the hepatorenal syndrome, common causes of acute kidney injury include prerenal azotemia and acute tubular necrosis in this population. Management involves hemodynamic support, renal replacement therapy, and mitigation of risk factors. Renal dysfunction in a cirrhotic patient usually implies a poor prognosis in the absence of liver transplantation. An important issue is the frequent need for kidney, in addition to liver, transplantation if renal insufficiency has been persistent in a decompensated cirrhotic.

Post transplant thrombotic microangiopathy causing acute renal failure

Acute Renal Failure (ARF) in the immediate post transplant period is most commonly due to acute tubular necrosis, acute cellular rejection and calcineurin inhibitor toxicity apart from usual prerenal and post renal causes. In this report, we discuss an interesting and unusual cause of ARF due to thrombotic micro angiopathy in the immediate post transplant setting.

Thrombotic microangiopathy after ABO-incompatible living donor liver transplantation: a case report

Thrombotic microangiopathy (TMA) has rarely been reported in the setting of liver transplantation. Herein we have reported a successful case of TMA after ABO-incompatible living donor liver transplantation (LDLT) treated with plasma exchange and high-dose intravenous gamma-globulin infusion. A 50-year-old woman was diagnosed with hepatitis C virus-related cirrhosis. We performed an ABO-incompatible LDLT (group B to O) with preoperative plasma exchange to reduce the anti-B hemagglutinin titers to 1:8. The immunosuppressants consisted of tacrolimus, mycophenolate mofetil, and steroid. On postoperative day (POD) 8, her anti-B hemagglutinin titer suddenly increased to 1:64. The serum lactate dehydrogenase (LDH) level was grossly elevated (1518 IU/L). On POD 13, we suspected infection of an intra-abdominal hematoma (Serratia marcescens) which was drained surgically. On day 5 after the reoperation, thrombocytopenia developed with a platelet count of 3 x 10(4)/mm3. A peripheral blood film showed severe red blood cell (RBC) fragmentation. Thus, we made a clinical diagnosis of TMA and reduced the tacrolimus dose. We started intensive daily plasma exchange (4 L/d) with fresh frozen plasma and high-dose intravenous gamma-globulin infusions. One week thereafter, thrombocytopenia improved with reduced transfusion requirements. The peripheral blood film showed normal RBC morphology. The serum LDH returned to baseline levels. Four factors were considered to have caused TMA in this case: the prescription of tacrolimus, ABO-incompatible liver transplantation, bacterial infection, and surgical stress. These factors may have all contributed by causing significant endothelial injury and TMA.

Haemolytic Uraemic Syndrome after Living-donor Liver Transplantation: Is Small-for-size Graft a Potential Risk Factor?

Haemolytic uraemic syndrome (HUS) is a rare complication of solid organ transplantation. Immunosuppressive drugs, including cyclosporin A and tacrolimus, have frequently been incriminated. Here we report a case of tacrolimus-induced HUS in a woman with small-for-size syndrome after living-donor liver transplantation. Hypertension, microangiopathic anaemia and end-stage renal failure occurred in the immediate post-transplant period; all other risk factors that might be implicated in the development of HUS were investigated and excluded if no evidence was found. A possible association between small-for-size syndrome, which frequently results in a high blood concentration of tacrolimus post-operatively, and the occurrence of HUS is discussed.

Synergistic interactions between interferon-gamma and TRAIL modulate c-FLIP in endothelial cells, mediating their lineage-specific sensitivity to thrombotic thrombocytopenic purpura plasma-associated apoptosis

Microvascular endothelial cell (MVEC) injury coupled to progression of platelet microthrombi facilitated by ADAMTS13 deficiency is characteristic of idiopathic and HIV-linked thrombotic thrombocytopenic purpura (TTP). Cytokines capable of inducing MVEC apoptosis in vitro are up-regulated in both TTP and HIV infection. However, the concentrations of these cytokines required to elicit EC apoptosis in vitro are 2- to 3-log-fold greater than present in patient plasmas. We report that clinically relevant levels of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and interferon (IFN)-gamma act in synergy to induce apoptosis in dermal MVECs, but have no effect on large-vessel ECs or pulmonary MVECs. This reflects the tissue distribution of TTP lesions in vivo. Sensitivity to TTP plasma or TRAIL plus IFN-gamma is paralleled by enhanced ubiquitination of the caspase-8 regulator cellular FLICE-like inhibitory protein (c-FLIP), targeting it for proteasome degradation. c-FLIP silencing with anti-FLIP short interfering RNA (siRNA) in pulmonary MVECs rendered them susceptible to TTP plasma- and cytokine-mediated apoptosis, while up-regulation of c-FLIP by gene transfer partially protected dermal MVECs from such injury. TTP plasma-mediated apoptosis appears to involve cytokine-induced acceleration of c-FLIP degradation, sensitizing cells to TRAIL-mediated caspase-8 activation and cell death. Suppression of TRAIL or modulation of immunoproteasome activity may have therapeutic relevance in TTP.

Plasma therapy in atypical haemolytic uremic syndrome: lessons from a family with a factor H mutation

Whilst randomised control trials are undoubtedly the best way to demonstrate whether plasma exchange or infusion alone is the best first-line treatment for patients with atypical haemolytic uremic syndrome (aHUS), individual case reports can provide valuable information. To that effect, we have had the unique opportunity to follow over a 10-year period three sisters with aHUS associated with a factor H mutation (CFH). Two of the sisters are monozygotic twins. A similar natural evolution and response to treatment would be expected for the three patients, as they all presented with the same at-risk polymorphisms for CFH and CD46 and no identifiable mutation in either CD46 or CFI. Our report of different modalities of treatment of the initial episode and of three transplantations and relapses in the transplant in two of them, strongly suggest that intensive plasma exchange, both acutely and prophylactically, can maintain the long-term function of both native kidneys and allografts. In our experience, the success of plasma therapy is dependent on the use of plasma exchange as opposed to plasma infusion alone, the prolongation of daily plasma exchange after normalisation of haematological parameters followed by prophylactic plasma exchange, the use of prophylactic plasma exchange prior to transplantation and the use of prophylactic plasma exchange at least once a week posttransplant with immediate intensification of treatment if there are any signs of recurrence.

Pathogenesis and prognosis of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is a clinicopathological syndrome characterized by thrombosis formation in the microvasculature of various organs. Included in the broad category of TMA are the hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Typical HUS is caused by Escherichia coli O157:H7, which produces the Shiga-like toxins; Stx-1 and Stx-2. In addition to damaging endothelial cells via the inhibition of protein synthesis, Shiga-like toxins also activate endothelial cells to produce inflammatory mediators, amplifying the prothrombogenic state. Although most patients with typical HUS recover renal functions, recent analysis has shown that typical HUS is not a benign disease in the long term. Genetic abnormalities of complement regulatory proteins predispose patients to atypical HUS. Mutations in factor H, membrane cofactor protein, and factor I are known to be associated with atypical HUS. Atypical HUS forms have a poor outcome and show recurrent and progressive courses. Autoimmune IgG inhibitors of a disintegrin and metalloprotease, with thrombospodin-1-like domains (ADAMTS) 13 and mutations of the ADAMTS13 gene lead to the development of TTP. Without treatment, TTP is associated with a very high mortality rate. As it is for atypical HUS, plasma exchange is currently the most feasible treatment for TTP. Etiological diagnosis at the bedside and the development of disease-specific therapeutic modalities will enable us to optimize the management of patients with TMA and improve their prognosis in the future.

Thrombotic microangiopathy after kidney transplantation

Two forms of post-transplant thrombotic microangiopathy (TMA) may be recognized: recurrent TMA and de novo TMA. Recurrent TMA may occur in patients who developed a nondiarrhoeal form of haemolytic uraemic syndrome (HUS) being particularly frequent in patients with autosomal recessive or dominant HUS. The recurrence is almost the rule in patients with mutation in complement factor H gene. Most patients eventually lose the graft. Treatment with plasma infusions or plasmapheresis is often disappointing, but few cases may be rescued. Intravenous immunoglobulins and rituximab have also been successful in anedoctic cases. De novo TMA is rarer. A number of factors including viral infection may be responsible of de novo TMA, but in most cases TMA is triggered by calcineurin inhibitors or mTOR inhibitors. The clinical presentation of de novo TMA may be variable with some patients showing clinical and laboratory features of HUS while others showing only a progressive renal failure. The prognosis is less severe than with recurrent TMA. Complete withdrawal of the offending drug may lead to improvement in many cases. The addition of plasma exchange may result in graft salvage in about 80% of cases.

Clinical Outcome of Thrombotic Microangiopathy after Living-Donor Liver Transplantation Treated with Plasma Exchange Therapy

Thrombotic microangiopathy (TMA) is a well-documented but severe complication that occurs after solid-organ transplant. Administration of calcineurin inhibitors is considered a major cause of this fatal complication; prompt initiation of plasma exchange therapy after reduction or conversion of calcineurin inhibitors has been recommended. Nevertheless, little is known about clinical evidence of this strategy against TMA after solid-organ, especially non-renal-organ, transplantation. Medical records of 63 patients who were hospitalized at Artificial Organ and Transplantation Division in Tokyo University Hospital and underwent blood purification therapy between January 1999 and May 2005 were reviewed. Twenty-eight living-donor liver transplantation (LDLT) recipients who received plasma exchange therapy were identified, and 18 of them were found retrospectively to receive a diagnosis of having TMA. Of the 18 patients, 10 (56%) responded to this therapy and survived after the treatment was stopped, whereas eight (44%) patients died before improvement. Subsequent follow-up of patients clarified that 1-yr survival rate of post-LDLT TMA was approximately 30%. Multivariate Cox proportional-hazards regression analysis demonstrated that the interval between transplant surgery and onset of TMA (hazard ratio 1.35 per 30 d; 95% confidence interval 1.07 to 1.71; P = 0.021) and pretreatment blood urea nitrogen level (hazard ratio 1.39 per 10 mg/dl; 95% confidence interval 1.02 to 1.90; P = 0.037) predicted mortality. Analyses identified post-LDLT recipients with TMA as being at high risk for poor prognosis. Effective strategies are needed for late-onset TMA after LDLT to improve treatment response and survival.

Genetic and functional analyses of membrane cofactor protein (CD46) mutations in atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is characterized by the triad of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. The non-Shiga toxin-associated HUS (atypical HUS [aHUS]) has been shown to be a disease of complement dysregulation. Mutations in the plasma complement regulators factor H and factor I and the widely expressed membrane cofactor protein (MCP; CD46) have been described recently. This study looked for MCP mutations in a panel of 120 patients with aHUS. In this cohort, approximately 10% of patients with aHUS (11 patients; nine pedigrees) have mutations in MCP. The onset typically was in early childhood. Unlike patients with factor I or factor H mutations, most of the patients do not develop end-stage renal failure after aHUS. The majority of patients have a mutation that causes reduced MCP surface expression. A small proportion expressed normal levels of a dysfunctional protein. As in other studies, incomplete penetrance is shown, suggesting that MCP is a predisposing factor rather than a direct causal factor. The low level of recurrence of aHUS in transplantation in patients with MCP mutations is confirmed, and the first MCP null individuals are described. This study confirms the association between MCP deficiency and aHUS and further establishes that a deficiency in complement regulation, specifically cofactor activity, predisposes to severe thrombotic microangiopathy in the renal vasculature.

Posttransplantation cytomegalovirus-induced recurrence of atypical hemolytic uremic syndrome associated with a factor H mutation: successful treatment with intensive plasma exchanges and ganciclovir

Atypical hemolytic uremic syndrome (HUS) can recur after renal transplantation and often leads to graft loss. In some series of familial HUS, the risk of early graft loss due to recurrence of HUS approaches 100% despite any therapy. This led some authors to claim that kidney transplantation is contraindicated in those patients. The authors describe an 8-year-old girl with end-stage renal failure owing to familial atypical HUS with a factor H mutation who underwent successful transplantation using continuous prophylactic plasma exchange (PE). Twenty-four months after transplantation, plasma creatinine level is 1.2 mg/dL (106 micromol/L) despite 2 recurrences of HUS contemporaneous to 2 cytomegalovirus infections, which resolved with PE intensification and ganciclovir. This strongly suggests that cytomegalovirus infection may trigger posttransplant recurrent HUS. The feasibility of kidney transplantation in case of atypical HUS related to factor H mutation using continuous prophylactic PE intensified during relapses should be confirmed in prospective studies.

Renal transplantation 2004: where do we stand today?

In spite of considerable progress in immunosuppressive and supportive treatment, numerous problems persist which interfere with the success of renal transplantation. Before transplantation has been performed, factors impacting on outcome include the donor (living vs cadaver, age and HLA system) as well as the recipient (age, immunological reactivity, potential sensitization and duration of dialysis). These are the main factors that affect the outcome of the transplant, particularly in the long-term. After transplantation a number of events may put graft function at risk: potential recurrence of the primary renal disease in the allograft; 'de novo' renal disease triggered by infections, drugs or autoimmunity; and non-specific progression promoters, such as diabetes, hypertension, proteinuria, nephrotoxic agents and/or viral infections. The two most frequent causes of chronic allograft dysfunction are (i) chronic rejection (often triggered by preceding acute rejection, delayed graft function or poor compliance) and (ii) calcineurin-inhibitor nephrotoxicity (more likely to develop in kidneys of older donors or in marginal kidneys). The differential diagnosis between these two entities is generally difficult, but some histological clues (reduplication of glomerular basement membrane, obliterating vasculopathy and C4d deposits) as well as the demonstration of humoral antibodies are pointers suggesting rejection. Treatment of chronic graft dysfunction is difficult, whatever the cause, particularly in cases with advanced renal lesions. Therefore, early diagnosis is of paramount importance. In this regard, graft biopsy can be of great help. In spite of many problems and complications, not only short-term but also long-term results of renal transplantation are improving progressively, as documented by CTS data showing that in Europe for transplants performed between 1982 and 1984 the mean graft half-life was 7 years, while for transplants performed between 1997 and 1999 it was 20 years.

Selective use of mycophenolate mofetil in renal transplant patients in Indian scenario

PURPOSE

Although mycophenolate mofetil (MMF) has emerged as a valuable immunosuppressive in renal transplantation, its high cost demands that it be used selectively.

MATERIALS AND METHODS

This retrospectively study included 55 renal transplant patients on MMF for rescue therapy after treatment of acute vascular rejection (n = 45), acute/chronic liver disease with elevated transaminases (n = 4), early chronic rejection (n = 2), cyclosporine toxicity (n = 3), and cyclosporine-induced hemolytic-uremic syndrome (n = 1). The patients were given 1.5 to 2 g MMF in divided doses for at least 6 months, depending upon the tolerability, adverse effects, and finances, and followed for 1 year. The patients on MMF following treatment of acute rejections were compared with controls who received azathioprine-based triple immunosuppression after treatment of an acute rejection episode.

RESULTS

The incidence of recurrent acute rejection in the first year was 18% in the MMF group compared to 42% in the control group (P < .005). The serum transaminases in the acute/chronic liver disease group reached normal levels at 3 to 6 months. The serum creatinine remained stable for a mean duration of 8 months in the early chronic rejection patients. The patients with cyclosporine toxicity showed stable graft function on low-dose cyclosporine. The patient with hemolytic-uremic syndrome showed stable graft function for 4 years. The MMF-based triple regimen is two times more expensive than an azathioprine-based regimen.

CONCLUSION

MMF significantly decreases the recurrence of acute rejection. It is a good alternative agent in special situations like acute/chronic liver diseases with elevated transaminases, early chronic rejection, cyclosporine toxicity, and cyclosporine-induced hemolytic-uremic syndrome. Because of the high cost it should be used selectively in our population.

Increased risk of thrombotic microangiopathy in patients receiving a cyclosporin-sirolimus combination

A single-center cohort study of kidney and kidney-pancreas recipients was conducted to evaluate the association between new immunosuppressive regimens and risk of thrombotic microangiopathy (TMA). From January 1st,1996 to December 31, 2002, 368 patients received a kidney or kidney-pancreas transplant at our center. Four immunosuppressive regimens were evaluated as potential risk factors of TMA: cyclosporin + mycophenolate mofetil (CsA + MMF), cyclosporin + sirolimus (CsA + SRL), tacrolimus + myophenolate mofetil (FK + MMF), and tacrolimus + sirolimus (FK + SRL). Thirteen patients developed biopsy-proven TMA in the absence of vascular rejection. The incidence of TMA was significantly different in the four immunosuppressive regimens studied (p < 0.001). The incidence of TMA was highest in the CsA + SRL group (20.7%). The relative risk of TMA was 16.1 [95% confidence interval (CI): 4.3-60.8] for patients in the CsA + SRL group as compared with those in the FK + MMF group. We also investigated in vitro the pathophysiological basis of this association. The CsA-SRL combination was found to be the only regimen that concomitantly displayed pro-necrotic and anti-angiogenic activities on arterial endothelial cells. We propose that this combination concurs to development of TMA through dual activities on endothelial cell death and repair.

Thienopyridine-linked thrombotic microangiopathy: association with endothelial cell apoptosis and activation of MAP kinase signalling cascades

The thienopyridine platelet antagonist ticlopidine is associated with development of thrombotic thrombocytopenic purpura (TTP) but the pathophysiology of this link is unclear. Severe deficiency of disintegrin and metalloproteinase with thrombospondin motif-13 (ADAMTS13), described in familial cases and a significant fraction of idiopathic TTP, has been reported in only a few ticlopidine-linked cases. As ticlopidine can disrupt production of extracellular matrix (ECM) components critical to microvascular endothelial cell (MVEC) integrity in vitro, we explored the hypotheses that ticlopidine and ticlopidine-linked TTP plasmas induce MVEC apoptosis in a manner similar to that of idiopathic TTP plasmas, and that ECM components and related mitogen-activated protein kinase (MAPK) signalling cascades may be involved in this process. Replicating the activity of plasmas from patients with idiopathic TTP, plasma from five ticlopidine-linked TTP patients induced apoptosis of primary human dermal, glomerular and hepatic MVEC, but had no effect on pulmonary MVEC or large vessel endothelial cells (EC). Pharmacological levels of ticlopidine initiated apoptosis with similar EC lineage restriction. In parallel, ticlopidine and plasmas from idiopathic and ticlopidine-TTP patients decreased transcripts for the ECM component thrombospondin-1 in MVEC, but not in large vessel EC. These changes were accompanied by prolonged induction of MAPKs extracellular signal-related kinase (ERK)-1/2 and p38 only in TTP susceptible MVEC. Induction of apoptosis by ticlopidine and TTP plasma was abrogated by inhibitors of ERK-1/2 and p38 phosphorylation. In conclusion, MVEC apoptosis related to altered ECM-MVEC interactions may be a key part of the pathology of ticlopidine-linked and idiopathic TTP.

The risk of recurrence of hemolytic uremic syndrome after renal transplantation in children

We reviewed the literature to analyze the risk of recurrence of hemolytic uremic syndrome (HUS) after renal transplantation in children. Among 118 children transplanted after post-diarrheal (D+) HUS, 1 (0.8%) had recurrence with graft loss. Among 63 children transplanted after HUS not associated with a prodrome of diarrhea (D-) of unknown mechanism, 13 (21%) had recurrence with graft loss. Of 11 patients with HUS associated with factor H deficiency who were transplanted, 5 lost the graft because of recurrence. Of 7 patients with HUS associated with normal factor H concentration but mutations in factor H gene who were transplanted, probably 2 had recurrence. Three patients with HUS associated with low serum C3, but no factor H deficiency or mutation lost their graft because of recurrence. The risk of recurrence in the autosomal recessive forms of HUS of unknown mechanism is not documented in children, but is around 60% in adults. A similar risk has been reported in the autosomal dominant forms. The only transplant patient with a constitutional deficiency of von Willebrand factor-cleaving protease had recurrence. Further efforts to document the post-transplant course of patients with D- HUS and progress in the understanding of the mechanisms and genetics of the disease are needed to allow more accurate prediction of the recurrence risk and to define therapeutic approaches.

Mutations in human complement regulator, membrane cofactor protein (CD46), predispose to development of familial hemolytic uremic syndrome

Membrane cofactor protein (MCP; CD46) is a widely expressed transmembrane complement regulator. Like factor H it inhibits complement activation by regulating C3b deposition on targets. Factor H mutations occur in 10-20% of patients with hemolytic uremic syndrome (HUS). We hypothesized that MCP mutations could predispose to HUS, and we sequenced MCP coding exons in affected individuals from 30 families. MCP mutations were detected in affected individuals of three families: a deletion of two amino acids (D237/S238) in family 1 (heterozygous) and a substitution, S206P, in families 2 (heterozygous) and 3 (homozygous). We evaluated protein expression and function in peripheral blood mononuclear cells from these individuals. An individual with the D237/S238 deletion had reduced MCP levels and approximately 50% C3b binding compared with normal controls. Individuals with the S206P change expressed normal quantities of protein, but demonstrated approximately 50% reduction in C3b binding in heterozygotes and complete lack of C3b binding in homozygotes. MCP expression and function was evaluated in transfectants reproducing these mutations. The deletion mutant was retained intracellularly. S206P protein was expressed on the cell surface but had a reduced ability to prevent complement activation, consistent with its reduced C3b binding and cofactor activity. This study presents further evidence that complement dysregulation predisposes to development of thrombotic microangiopathy and that screening patients for such defects could provide informed treatment strategies.

Renal transplantation in patients with hemolytic uremic syndrome: high rate of recurrence and increased incidence of acute rejections

BACKGROUND

The reported outcome of renal transplantation in patients with the hemolytic uremic syndrome (HUS) varies greatly, probably related to the diverse causes of HUS. In this single-center retrospective study, we have analyzed the recurrence rate, the incidence of acute rejections, and graft survival in patients suffering from adult-onset and childhood-onset HUS.

METHODS

The medical records of 35 patients with end-stage renal disease caused by HUS, who received 50 renal allografts, were reviewed. A definite recurrence of HUS was diagnosed if both clinical and histologic signs of thrombotic microangiopathy (TMA) were present in the absence of any endovasculitis. If there were signs of mild endovasculitis, a probable recurrence was diagnosed.

RESULTS

After first renal transplantation, 0 definite and 1 (6%) probable recurrence occurred in 18 patients with childhood-onset HUS, as opposed to 7 (41%) definite and 3 (18%) probable recurrences in 17 adult-onset HUS patients (odds ratio [OR], 13.4; 95% confidence interval [CI], 1.7-105.7). In the latter patients, early use of cyclosporine A increased the risk for recurrence. The incidence of acute rejections was increased compared with matched controls (OR, 1.52; 95% CI, 1.05-2.19 for adult-onset HUS and OR, 1.88; 95% CI, 1.34-2.62 for childhood-onset HUS). One-year graft survival in adult-onset HUS was poor (29%), whereas 1-year graft survival in childhood-onset HUS was comparable to matched controls.

CONCLUSIONS

In adult-onset HUS, the recurrence rate and the incidence of acute rejections are high, resulting in a detrimental graft survival. In childhood-onset HUS, the recurrence rate is low, but the posttransplantation course is complicated by an increased incidence of acute rejections.