Fadi Fakhouri

Use of eculizumab for atypical haemolytic uraemic syndrome and C3 glomerulopathies

In the past decade, a large body of evidence has accumulated in support of the critical role of dysregulation of the alternative complement pathway in atypical haemolytic uraemic syndrome (aHUS) and C3 glomerulopathies. These findings have paved the way for innovative therapeutic strategies based on complement blockade, and eculizumab, a monoclonal antibody targeting the human complement component 5, is now widely used to treat aHUS. In this article, we review 28 case reports and preliminary data from 37 patients enrolled in prospective trials of eculizumab treatment for episodes of aHUS involving either native or transplanted kidneys. Eculizumab may be considered as an optimal first-line therapy when the diagnosis of aHUS is unequivocal and this treatment has the potential to rescue renal function when administered early after onset of the disease. However, a number of important issues require further study, including the appropriate duration of treatment according to an individuals genetic background and medical history, the optimal strategy to prevent post-transplantation recurrence of aHUS and a cost–efficacy analysis. Data regarding the efficacy of eculizumab in the control of C3 glomerulopathies are more limited and less clear, but several observations suggest that eculizumab may act on the most inflammatory forms of this disorder.

Genetics and Outcome of Atypical Hemolytic Uremic Syndrome: A Nationwide French Series Comparing Children and Adults

BACKGROUND AND OBJECTIVES Atypical hemolytic uremic syndrome (aHUS) is a rare complement-mediated kidney disease that was first recognized in children but also affects adults. This study assessed the disease presentation and outcome in a nationwide cohort of patients with aHUS according to the age at onset and the underlying complement abnormalities. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A total of 214 patients with aHUS were enrolled between 2000 and 2008 and screened for mutations in the six susceptibility factors for aHUS and for anti-factor H antibodies. RESULTS Onset of aHUS occurred as frequently during adulthood (58.4%) as during childhood (41.6%). The percentages of patients who developed the disease were 23%, 40%, 70%, and 98% by age 2, 18, 40, and 60 years, respectively. Mortality was higher in children than in adults (6.7% versus 0.8% at 1 year) (P=0.02), but progression to ESRD after the first aHUS episode was more frequent in adults (46% versus 16%; P<0.001). Sixty-one percent of patients had mutations in their complement genes. The renal outcome was not significantly different in adults regardless of genetic background. Only membrane cofactor protein (MCP) and undetermined aHUS were less severe in children than adults. The frequency of relapse after 1 year was 92% in children with MCP-associated HUS and approximately 30% in all other subgroups. CONCLUSION Mortality rate was higher in children than adults with aHUS, but renal prognosis was worse in adults than children. In children, the prognosis strongly depends on the genetic background.

Recessive mutations in DGKE cause atypical hemolytic-uremic syndrome

Pathologic thrombosis is a major cause of mortality. Hemolytic-uremic syndrome (HUS) features episodes of small-vessel thrombosis resulting in microangiopathic hemolytic anemia, thrombocytopenia and renal failure. Atypical HUS (aHUS) can result from genetic or autoimmune factors that lead to pathologic complement cascade activation. Using exome sequencing, we identified recessive mutations in DGKE (encoding diacylglycerol kinase ɛ) that co-segregated with aHUS in nine unrelated kindreds, defining a distinctive Mendelian disease. Affected individuals present with aHUS before age 1 year, have persistent hypertension, hematuria and proteinuria (sometimes in the nephrotic range), and develop chronic kidney disease with age. DGKE is found in endothelium, platelets and podocytes. Arachidonic acid–containing diacylglycerols (DAG) activate protein kinase C (PKC), which promotes thrombosis, and DGKE normally inactivates DAG signaling. We infer that loss of DGKE function results in a prothrombotic state. These findings identify a new mechanism of pathologic thrombosis and kidney failure and have immediate implications for treating individuals with aHUS.

C3 glomerulopathy: consensus report

C3 glomerulopathy is a recently introduced pathological entity whose original definition was glomerular pathology characterized by C3 accumulation with absent or scanty immunoglobulin deposition. In August 2012, an invited group of experts (comprising the authors of this document) in renal pathology, nephrology, complement biology, and complement therapeutics met to discuss C3 glomerulopathy in the first C3 Glomerulopathy Meeting. The objectives were to reach a consensus on: the definition of C3 glomerulopathy, appropriate complement investigations that should be performed in these patients, and how complement therapeutics should be explored in the condition. This meeting report represents the current consensus view of the group.

Pregnancy-Associated Hemolytic Uremic Syndrome Revisited in the Era of Complement Gene Mutations

In contrast to pregnancy-associated thrombotic thrombocytopenic purpura, the pathogenesis and presentation of pregnancy-associated atypical hemolytic uremic syndrome (P-aHUS) remain ill-defined. We conducted a retrospective study to assess the presentation and outcomes of patients presenting with P-aHUS and the prevalence of alternative C3 convertase dysregulation. P-aHUS occurred in 21 of the 100 adult female patients with atypical HUS, with 79% presenting postpartum. We detected complement abnormalities in 18 of the 21 patients. The outcomes were poor: 62% reached ESRD by 1 month and 76% by last follow-up. The risk for P-aHUS was highest during a second pregnancy. Thirty-five women, 26 (74%) of whom had complement abnormalities, had at least one pregnancy before the onset of a non-pregnancy-related aHUS. Outcomes did not differ between patients with pregnancy-related and non-pregnancy-related aHUS. Mutations in the SCR19-20 domains of factor H were less frequent in P-aHUS patients compared with non-pregnancy-related aHUS. Pregnancies in female patients with complement abnormalities (n = 44) were complicated by fetal loss and preeclampsia in 4.8% and 7.7%, respectively. Better understanding of complement dysregulation in pregnancy complications is essential, especially to guide development of pharmacologic agents to modulate this system.

Primary glomerulonephritis with isolated C3 deposits: a new entity which shares common genetic risk factors with haemolytic uraemic syndrome

Introduction: Abnormal control of the complement alternative pathway (CAP) (factor H, factor I and membrane cofactor protein (MCP) deficiencies) is a well established risk factor for the occurrence of haemolytic uraemic syndrome (HUS). In some instances, HUS may be associated with an unusual glomerulonephritis with isolated C3 deposits (glomerulonephritis C3). We determined whether HUS and glomerulonephritis C3 share common genetic susceptibility factors. Methods: We identified 19 patients with glomerulonephritis C3. We measured levels of circulating complement components, performed assays for the detection of C3 nephritic factor (C3NeF) and screened factor H, factor I and MCP coding genes for the presence of mutations. Results: Patients were divided in two groups based on renal pathology findings: group I (n = 13) had typical features of type I membranoproliferative glomerulonephritis (glomerulonephritis C3 with membranoproliferative glomerulonephritis (MPGN)) and group II (n = 6) was characterised by mesangial and epimembranous C3 deposits in the absence of mesangial proliferation (glomerulonephritis C3 without MPGN). Mutations in complement regulatory genes were detected in 4/6 patients with glomerulonephritis C3 without MPGN (heterozygous mutations in factor H gene (two patients) with low factor H antigenic level in one case, heterozygous mutations in factor I gene (two patients)) and in only 2/13 patients with glomerulonephritis C3 with MPGN (heterozygous mutations in factor H gene (one patient) and double heterozygous mutation in CD 46 gene (one patient)). In contrast, C3NeF was present in 5/13 patients with glomerulonephritis C3 with MPGN and in 2/6 patients with glomerulonephritis C3 without MPGN, one of whom had a factor H mutation. Conclusion: HUS and glomerulonephritis C3 without MPGN share common genetic risk factors. Constitutional or acquired dysregulation of the CAP is probably associated with a wide spectrum of diseases, ranging from HUS to glomerulonephritis C3 with MPGN.

C3 glomerulopathy: a new classification.

Several distinct pathological patterns of glomerular inflammation are associated with abnormal regulation of the complement system, specifically, with dysregulation of the alternative pathway of the complement system. However, these conditions share the pathological finding of complement C3 (C3) deposited within the glomerulus in the absence of substantial immunoglobulin. This finding has alerted us and others to the possible presence of genetic and acquired complement dysregulation in individual patients. This article summarizes our current understanding of the relationship between dysregulation of the complement system and glomerular inflammation. Here, we suggest that glomerular pathologies that are characterized by the isolated deposition of C3 could usefully be classified by the term C3 glomerulopathy. In our view, this classification would alert the pathologist and nephrologist to the importance of screening for acquired and genetic abnormalities in complement regulation. In the future, it could help to identify individuals who might benefit from therapeutic inhibition of the complement system.

Angiotensin II Activates Collagen I Gene Through a Mechanism Involving the MAP/ER Kinase Pathway

Vascular remodeling and rearrangement of the extracellular matrix formation are among the major adaptive mechanisms to chronic increase in blood pressure. In previous studies we have found that angiotensin II (Ang II) participates in the hypertension-associated aortic and renal vascular fibrosis by stimulating collagen type I formation. The purpose of the present study was to gain insight into the molecular events that lead from the Ang II receptor to collagen I gene activation. To this end, we used a novel strain of transgenic mice harboring the luciferase gene under the control of the collagen I-&agr;2 chain promoter [procol&agr;2(I)]. Ang II produced an early (1 hour) 2- to 3-fold stimulation of procol&agr;2(I) activity in freshly isolated aortas and renal cortical slices (P <0.01) followed by similar increase in procol&agr;2(I) mRNA aortic levels. This effect of Ang II was inhibited by AT1-receptor antagonism (candesartan) and blockade of the MAPK/ERK cascade (PD98059); in contrast, inhibition of the P38 kinase pathway (SB202190) and blockade of the release of the transcription factor NF&kgr;B (PDTC) did not have any effect in the Ang II–induced activation of the collagen I gene. In addition, Ang II induced a rapid (5 minutes) increase of the MAPK/ERK activity that was accompanied by increased expression (3-fold) of the c-fos proto-oncogene. This increase of c-fos mRNA expression was blocked by PD98059; in addition, curcumin, a blocker of the transcriptional factor AP-1, canceled the effect of Ang II on the collagen I gene. Decorin, a scavenger of the active form of transforming growth factor-&bgr; (TGF-&bgr;), canceled the Ang II effect on collagen I gene, whereas inhibition of the MAPK/ERK pathway had no effect on the TGF-&bgr;–induced activation of procol&agr;2(I). These data indicate that the cellular events after AT1 receptor stimulation and leading to activation of collagen I gene expression require activation of both the MAPK/ERK and TGF-&bgr; signaling pathways.

An international consensus approach to the management of atypical hemolytic uremic syndrome in children

Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of complement dysregulation. This advance facilitated the development of novel, rational treatment options targeting terminal complement activation, e.g., using an anti-C5 antibody (eculizumab). We review treatment and patient management issues related to this therapeutic approach. We present consensus clinical practice recommendations generated by HUS International, an international expert group of clinicians and basic scientists with a focused interest in HUS. We aim to address the following questions of high relevance to daily clinical practice: Which complement investigations should be done and when? What is the importance of anti-factor H antibody detection? Who should be treated with eculizumab? Is plasma exchange therapy still needed? When should eculizumab therapy be initiated? How and when should complement blockade be monitored? Can the approved treatment schedule be modified? What approach should be taken to kidney and/or combined liver–kidney transplantation? How should we limit the risk of meningococcal infection under complement blockade therapy? A pressing question today regards the treatment duration. We discuss the need for prospective studies to establish evidence-based criteria for the continuation or cessation of anticomplement therapy in patients with and without identified complement mutations.

Thrombotic microangiopathy secondary to VEGF pathway inhibition by sunitinib

BACKGROUND Drugs targeting the VEGF pathway are associated with renal adverse events, including proteinuria, hypertension and thrombotic microangiopathy (TMA). Most cases of TMA are reported secondary to bevacizumab. It was shown recently that sunitinib, a small molecule inhibiting several tyrosine kinase receptors, including VEGF receptors, can also induce proteinuria, hypertension and biological features of TMA. Case. A 44-year-old woman with a history of malignant skin hidradenoma was started on sunitinib for refractory disease. She developed hypertension after 2 weeks and low-grade proteinuria after 4 weeks. Renal function remained normal, and biological signs of TMA were absent. A renal biopsy was performed 6 months later as proteinuria persisted, demonstrating typical features of TMA. The patient was given irbesartan, and sunitinib was continued for 3 months after diagnosis. Over this period, blood pressure and renal function remained stable and proteinuria became undetectable. CONCLUSION We report on the first case of histologically documented TMA secondary to sunitinib and provide detailed description of renal histological involvement. This suggests that all anti-VEGF drugs may share a common risk for developing renal adverse events, including TMA. Our case highlights the possible discrepancy between mild clinical manifestation on one hand and severe TMA features on renal biopsy on the other hand and pleads for large indication of renal biopsy in this setting. The renin-angiotensin system blockers may be considered in patients with mild clinical manifestations and in the absence of therapeutic alternative to anti-VEGF drugs.