A time for reappraisal of "atypical" hemolytic uremic syndrome: should all patients be treated the same?

Profile and Post-Kidney Retrieval Outcomes in Asymptomatic Kidney Donors With Genetic Mutations in Complement Factors–Related Genes

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder triggered by various stressors. Most of the time, stressors may not be identified in patients with aHUS. The disease may remain quiescent without manifestation throughout life.

BACKGROUND

To assess the outcome of an asymptomatic carrier of genetic mutations of patients with aHUS who had undergone donor kidney retrieval surgery.

METHODS

We retrospectively included the patients diagnosed with a genetic abnormality in complement factor H (CHF) or CHF-related (CFHR) genes without manifestation of the aHUS and who had undergone donor kidney retrieval surgery. The data were analyzed with descriptive statistics.

RESULTS

Among patients who were the kidney recipients from the prospective donors, 6 donors were screened for genetic mutations in CFH and CFHR genes. Four donors showed positive mutation for CFH and CFHR. The mean age was 54.5 years (range, 50-64 years). After over a year since donor kidney retrieval surgery, all prospective mother donors are alive without aHUS activation and with a normal kidney function on a single kidney.

CONCLUSION

Asymptomatic carriers of genetic mutations in CFH and CFHR can be the prospective donors for their first-degree family member who have active aHUS. A genetic mutation in an asymptomatic donor should not be a contraindication for refuting the prospective donor.

C3 glomerulopathy and atypical hemolytic uremic syndrome: an updated review of the literature on alternative complement pathway disorders

The complement system plays a significant role within the pathological process of C3 glomerulopathy (C3GP) and atypical hemolytic uremic syndrome (aHUS). In daily practice, clinicians should differentiate the subgroups of C3GP because of they should apply different treatment modalities. In the past, C3GP was considered as a part of membranoproliferative glomerulonephritis (MPGN). MPGN is defined as glomerular capillary thickening secondary to the synthesis of the new glomerular basement membrane and mesangial cellular hyperplasia with mesangial matrix expansion. Atypical hemolytic uremic syndrome is an ultra-rare disease that can be outlined by the triad of Coombs negative microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Recent advances demonstrated that these diseases share common abnormalities of the control of the alternative complement system. Therefore, nowadays, most researchers advocate that there may be overlap in the pathogenesis of C3GP and aHUS. This review will provide recent novel mechanisms and treatment options in these diseases. For the purposes that we mentioned above and to help clinicians, we aimed to describe the etiology, pathophysiology, and treatment of C3GP and aHUS in this comprehensive review.

New insights into the pathogenesis of Streptococcus pneumoniae-associated hemolytic uremic syndrome

The purpose of this review is to describe Streptococcus pneumoniae-associated hemolytic uremic syndrome (P-HUS) with emphasis on new insights into the pathophysiology and management over the past 10 years. Even though awareness of this clinico-pathological entity has increased, it likely remains under-recognized. Recent observations indicate that although neuraminidase activity and exposure of the T-antigen are necessary for development of P-HUS, they are not sufficient; activation of the alternate pathway of complement may also contribute. It is unclear, however, whether or not eculizumab and/or plasmapheresis are of value.

First-Line, Early and Long-Term Eculizumab Therapy in Atypical Hemolytic Uremic Syndrome: A Case Series in Pediatric Patients

INTRODUCTION

Studies relating to first-line, early, and long-term eculizumab treatment and outcomes in children with atypical hemolytic uremic syndrome (aHUS) are scarce and unclear. The aim of this case-series study was to evaluate the outcomes of first-line, early, and long-term eculizumab treatment in our aHUS patients.

MATERIALS AND METHODS

We reviewed the data from four pediatric patients with aHUS who were treated with eculizumab. In three of them, eculizumab was used as a first-line therapy, and the follow-up period was ≥2 years in three patients.

RESULTS

Plasma exchange could not be performed in any patient. Plasma infusions were used only in Patient 1 (a 14-month-old boy) for 8 days without any response. Therefore, eculizumab was started on day 11 after admission. Patient 2 (a 16-month-old boy), Patient 3 (an 11-year-old girl), and Patient 4 (a 32-month-old girl) were treated with eculizumab as a first-line therapy, which was started 2-4 days after admission. The dosage of eculizumab was adjusted according to body weight. The hematologic parameters (the time frames were 3-17 days) and C ₃ (the time frames were 10-17 days) returned to normal in all patients after receipt of eculizumab. Although Patient 1 developed stage III chronic kidney disease, complete renal recovery occurred in Patients 2 and 4. Patient 3 also had reflux nephropathy with bilateral grade III vesicoureteral reflux and renal scars. Her creatinine clearance returned to the baseline value after receiving eculizumab. No complications related to eculizumab were observed in any patient during the follow-up period.

CONCLUSION

Eculizumab can be successfully used as a first-line therapy in pediatric aHUS patients. We observed that the early initiation of eculizumab was associated with the complete recovery of renal function.

Monitoring of complement activation biomarkers and eculizumab in complement-mediated renal disorders

Various complement-mediated renal disorders are treated currently with the complement inhibitor eculizumab. By blocking the cleavage of C5, this monoclonal antibody prevents cell damage caused by complement-mediated inflammation. We included 23 patients with atypical haemolytic uraemic syndrome (aHUS, n = 12), C3 glomerulopathies (C3G, n = 9) and acute antibody-mediated renal graft rejection (AMR, n = 2), treated with eculizumab in 12 hospitals in Germany. We explored the course of complement activation biomarkers and the benefit of therapeutic drug monitoring of eculizumab. Complement activation was assessed by analysing the haemolytic complement function of the classical (CH50) and the alternative pathway (APH50), C3 and the activation products C3d, C5a and sC5b-9 prior to, 3 and 6 months after eculizumab treatment. Eculizumab concentrations were determined by a newly established specific enzyme-linked immunosorbent assay (ELISA). Serum eculizumab concentrations up to 1082 μg/ml point to drug accumulation, especially in paediatric patients. Loss of the therapeutic antibody via urine with concentrations up to 56 μg/ml correlated with proteinuria. In aHUS patients, effective complement inhibition was demonstrated by significant reductions of CH50, APH50, C3d and sC5b-9 levels, whereas C5a levels were only reduced significantly after 6 months' treatment. C3G patients presented increased C3d and consistently low C3 levels, reflecting ongoing complement activation and consumption at the C3 level, despite eculizumab treatment. A comprehensive complement analysis together with drug monitoring is required to distinguish mode of complement activation and efficacy of eculizumab treatment in distinct renal disorders. Accumulation of the anti-C5 antibody points to the need for a patient-orientated tailored therapy.

Atypical hemolytic uremic syndrome: a clinical conundrum

BACKGROUND

Patients negative for Shiga toxin-producing E. coli (STEC) are categorized as having atypical hemolytic uremic syndrome (HUS) and are associated with an increased risk for complement mutations and poorer prognosis compared with typical HUS. However, STEC identification is limited by the natural history of HUS.

METHODS

The current study is aimed at identifying HUS patients with poor outcomes based on the presence or absence of diarrhea (D) or Shiga toxin (S). A single-center retrospective review (2003-2012) of 42 HUS patients (follow-up 31.3 ± 38.7 months) was carried out. HUS was managed clinically with supportive treatments such as dialysis, plasma therapy, and eculizumab.

RESULTS

There was no significant difference in the D+S+ (31 %), D+S- (50 %) and D-S- (19 %) groups in the outcome variables of chronic kidney disease stages I-II (100 % vs 81 % vs 67 %) and proteinuria at follow-up (20 % vs 12.5 % vs 33.3 %), hospitalization duration (16.0 ± 8.7 vs 18.1 ± 9.5 vs 23.7 ± 12.9 days); dialysis requirement (50 % vs 81 % vs 66.7 %), and dialysis duration (10.2 ± 1.9 vs 33.3 ± 72.8 vs 10.3 ± 8.1 days). There was no significant difference in study outcomes in STEC+ (59 %) versus STEC- (41 %) groups. Genetic testing was performed in 12 % of HUS patients based on age, recurrent HUS, familial HUS, persistently low C3, or prolonged dialysis, and 80 % of the patients tested were positive for genetic mutations.

CONCLUSIONS

Our study does not show poorer outcomes in STEC- HUS. Indications and the cost-effectiveness of genetic testing, eculizumab, and plasmapheresis in STEC- HUS need to be evaluated further.

Critical appraisal of eculizumab for atypical hemolytic uremic syndrome

The biology of atypical hemolytic uremic syndrome has been shown to involve inability to limit activation of the alternative complement pathway, with subsequent damage to systemic endothelial beds and the vasculature, resulting in the prototypic findings of a thrombotic microangiopathy. Central to this process is the formation of the terminal membrane attack complex C5b-9. Recently, application of a monoclonal antibody that specifically binds to C5, eculizumab, became available to treat patients with atypical hemolytic uremic syndrome, replacing plasma exchange or infusion as primary therapy. This review focuses on the evidence, based on published clinical trials, case series, and case reports, on the efficacy and safety of this approach.

Post-streptococcal glomerulonephritis associated with atypical hemolytic uremic syndrome: to treat or not to treat with eculizumab?

A 7-year-old male with poststreptococcal glomerulonephritis (PSGN) developed hemolytic uremic syndrome (HUS) and achieved remission. He was treated with eculizumab for 1 year. The eculizumab was discontinued and the patient remained in remission. This is the 10th reported case of PSGN associated with HUS. The histopathological feature observed at the 1-year follow-up was indistinguishable from the expected findings in an individual with healed PSGN without associated HUS. The relatively good prognosis in most prior cases and the absence of any reported recurrences strongly suggest that this form of atypical HUS does not warrant long-term eculizumab therapy.

First-line therapy in atypical hemolytic uremic syndrome: consideration on infants with a poor prognosis

Background

Atypical hemolytic uremic syndrome (aHUS) is a rare and heterogeneous disorder. The first line treatment of aHUS is plasma therapy, but in the past few years, the recommendations have changed greatly with the advent of eculizumab, a humanized monoclonal anti C5-antibody. Although recent recommendations suggest using it as a primary treatment for aHUS, important questions have arisen about the necessity of immediate use of eculizumab in all cases. We aimed to draw attention to a specific subgroup of aHUS patients with rapid disease progression and high mortality, in whom plasma therapy may not be feasible.

Methods

We present three pediatric patients of acute complement-mediated HUS with a fatal outcome. Classical and alternative complement pathway activity, levels of complement factors C3, C4, H, B and I, as well as of anti-factor H autoantibody and of ADAMTS13 activity were determined. The coding regions of CFH, CFI, CD46, THBD, CFB and C3 genes were sequenced and the copy number of CFI, CD46, CFH and related genes were analyzed.

Results

We found severe activation and consumption of complement components in these patients, furthermore, in one patient we identified a previously not reported mutation in CFH (Ser722Stop), supporting the diagnosis of complement-mediated HUS. These patients were not responsive to the FFP therapy, and all cases had fatal outcome.

Conclusion

Taking the heterogeneity and the variable prognosis of atypical HUS into account, we suggest that the immediate use of eculizumab should be considered as first-line therapy in certain small children with complement dysregulation.

Current treatment of atypical hemolytic uremic syndrome

Tremendous advances have been made in understanding the pathogenesis of atypical Hemolytic Uremic Syndrome (aHUS), an extremely rare disease. Insights into the molecular biology of aHUS resulted in rapid advances in treatment with eculizumab (Soliris(®), Alexion Pharmaceuticals Inc.). Historically, aHUS was associated with very high rates of mortality and morbidity. Prior therapies included plasma therapy and/or liver transplantation. Although often life saving, these were imperfect and had many complications. We review the conditions included under the rubric of aHUS: S. pneumoniae HUS (SpHUS), inborn errors of metabolism, and disorders of complement regulation, emphasizing their differences and similarities. We focus on the clinical features, diagnosis, and pathogenesis, and treatment of aHUS that results from mutations in genes encoding alternative complement regulators, SpHUS and HUS associated with inborn errors of metabolism. Mutations in complement genes, or antibodies to their protein products, result in unregulated activity of the alternate complement pathway, endothelial injury, and thrombotic microangiopathy (TMA). Eculizumab is a humanized monoclonal antibody that inhibits the production of the terminal complement components C5a and the membrane attack complex (C5b-9) by binding to complement protein C5a. This blocks the proinflammatory and cytolytic effects of terminal complement activation. Eculizumab use has been reported in many case reports, and retrospective and prospective clinical trials in aHUS. There have been few serious side effects and no reports of tachphylaxis or drug resistance. The results are very encouraging and eculizumab is now recognized as the treatment of choice for aHUS.