A 'silent', new polymorphism of factor H and apparent de novo atypical haemolytic uraemic syndrome after kidney transplantation

Eculizumab Rescue Therapy in Patients with Recurrent Atypical Hemolytic Uremic Syndrome After Kidney Transplantation

Introduction

Since 2016, kidney transplantation in patients with atypical hemolytic uremic syndrome (aHUS) in the Netherlands is performed without eculizumab prophylaxis. Eculizumab is given in case of posttransplant aHUS recurrence. Eculizumab therapy is monitored in the CUREiHUS study.

Methods

All participating kidney transplant patients who received eculizumab therapy for a suspected posttransplant aHUS recurrence were evaluated. Overall recurrence rate was monitored prospectively at Radboud University Medical Center.

Results

In the period from January 2016 until October 2020, we included 15 (12 females, 3 males; median age 42 years, range 24-66 years) patients with suspected aHUS recurrence after kidney transplantation in this study. The time interval to recurrence showed a bimodal distribution. Seven patients presented early after transplantation (median 3 months, range 0.3-8.8 months), with typical aHUS features: rapid loss of estimated glomerular filtration rate (eGFR) and laboratory signs of thrombotic microangiopathy (TMA). Eight patients presented late (median 46 months, range 18-69 months) after transplantation. Of these, only 3 patients had systemic TMA, whereas 5 patients presented with slowly deteriorating eGFR without systemic TMA. Treatment with eculizumab resulted in improvement or stabilization of eGFR in 14 patients. Eculizumab discontinuation was tried in 7 patients; however, it was successful only in 3. At the end of the follow-up (median 29 months, range 3-54 months after start of eculizumab), 6 patients had eGFR <30 ml/min per 1.73 m². Graft loss had occurred in 3 of them. Overall, aHUS recurrence rate without eculizumab prophylaxis was 23%.

Conclusions

Rescue treatment of posttransplant aHUS recurrence is effective; however, some patients suffer from irreversible loss of kidney function, likely caused by delayed diagnosis and treatment and/or too aggressive discontinuation of eculizumab. Physicians should be aware that recurrence of aHUS can present without evidence of systemic TMA.

De Novo and Recurrent Thrombotic Microangiopathy After Renal Transplantation: Current Concepts in Management

Thrombotic microangiopathy is a well-recognized complication of kidney transplantation that leads frequently to allograft failure. This serious outcome can greatly depend on the underlying etiology and on the timing of therapeutic interventions. Thrombotic microangiopathy syndrome may occur with no previous history of thrombotic microangiopathy (that is, de novo thrombotic microangiopathy), mostly due to medica tions or infections. More frequently, it may recur after kidney transplant in patients with endstage renal failure due to atypical hemolytic uremic syndrome. However, for patients with Shiga-toxininduced hemolytic uremic syndrome, particularly pediatric patients, there is a favorable prognosis. A fundamental tool for management of this disease is genetic screening for abnormal mutations; this can recognize the suggested approach of therapy and may determine the outcome of the disease to a large extent. Although patients with complement factor H and I mutations have worse prognosis, other patients with membrane cofactor protein mutations, for example, have a more favorable prognosis. Accordingly, the plan of therapy can be tailored with a better chance of cure. Unfortunately, the successful use of the biological agent eculizumab, an anti-C5 agent, in some of these syndromes is largely impeded by its high cost, which is linked to its use as a life-long therapy. However, newly suggested therapeutic options may ameliorate this drawback.

Poor allograft outcome in Indian patients with post-transplant C3 glomerulopathy

Background

Complement 3 glomerulopathy (C3G) results from dysfunction of the alternative complement pathway (ACP). No data are available on post-transplant C3G in South Asia.

Methods

In this study, renal allograft biopsies of C3G patients performed from 2012 to 2017 were analysed for ACP functional assay (APFA), serum complement levels, complement factor H (CFH), complement factor B (CFB) and autoantibodies to CFH and CFB. Limited genetic screening for CFH/CFHR5 genes was carried out. All study patients were also followed up.

Results

A total of 21 cases of C3G were included, of which 11 had native C3G disease (that is, recurrent C3G). Of these 11 recurrent cases, 7 presented with allograft dysfunction and 4 with proteinuria and renal dysfunction. Early post-transplant recurrence (<1 month) was noted in six patients, whereas recurrence in five patients occurred within 8–17 months of transplant. Biopsies showed mild focal mesangial expansion with or without endocapillary proliferation and thrombotic microangiopathy. Rejection was also noted in six patients. APFA/C3 levels were low in all cases. Serum CFH levels were low [dense deposit disease (DDD), 44%; C3 glomerulonephritis (C3GN), 25%], whereas CFB levels were normal. Autoantibodies to CFH, CFB and C3 nephritic factor were present in 11, 0 and 44% of DDD cases, respectively, and in 17, 17 and 33% of C3GN cases, respectively. Genetic analysis revealed only non-pathogenic CFH gene variants (93%). No novel mutation was found. At follow-up (140 months), stable graft was noted in 28% of cases, progressive renal failure in 19%, graft loss in 34%, and 19% of patients died.

Conclusion

Post-transplant C3G can present with graft dysfunction and/or proteinuria. Subtle histological findings demand careful interpretation of immunofluorescence results. Autoantibodies to complement pathway regulatory proteins are common, and no novel mutation has been found from limited genetic workup. Clinical outcome is poor.

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.

Complement in Kidney Transplantation

The complement system is considered to be an important part of innate immune system with a significant role in inflammation processes. The activation can occur through classical, alternative, or lectin pathway, resulting in the creation of anaphylatoxins C3a and C5a, possessing a vast spectrum of immune functions, and the assembly of terminal complement cascade, capable of direct cell lysis. The activation processes are tightly regulated; inappropriate activation of the complement cascade plays a significant role in many renal diseases including organ transplantation. Moreover, complement cascade is activated during ischemia/reperfusion injury processes and influences delayed graft function of kidney allografts. Interestingly, complement system has been found to play a role in both acute cellular and antibody-mediated rejections and thrombotic microangiopathy. Therefore, complement system may represent an interesting therapeutical target in kidney transplant pathologies.