Systematic review of atypical hemolytic uremic syndrome biomarkers

Inborn errors of immunity with kidney and urinary tract disorders: a review

Human inborn errors of immunity (IEIs), previously referred to as primary immunodeficiency disorders (PIDs), are a heterogeneous spectrum of inherited abnormalities of the immune system with different organ involvement. The number of identified IEIs is rapidly increasing, highlighting the non-negligible role of an interdisciplinary approach in clinical diagnosis. Kidney disorders are one of the important comorbidities in some of the affected patients and play a significant role in the diagnosis and course of disease. According to recent studies, 22 types of human IEI with renal manifestations have been identified so far, including immunodeficiency with congenital thrombocytopenia, thymic defects with additional congenital anomalies, complement deficiencies, type 1 interferonopathies, immunity related to non-hematopoietic tissues, congenital neutropenia's, common variable immunodeficiency disorder (CVID) phenotype and immuno-osseous dysplasia. Based on this classification, we herein review IEIs with renal features and explain the genetic defect, inheritance, and type of renal manifestations.

Usefulness and analytical performances of complement multiplex assay for measuring complement biomarkers in plasma

INTRODUCTION

The complement system is involved in numerous diseases, through diverse mechanisms and degree of activation. With the emergence of complement targeting therapeutic, simple and accessible tools to evaluate the extent of complement activation are strongly needed.

METHODS

We evaluated two multiplex panels, measuring complement activation fragments (C4a, C3a, C5a, Bb, Ba, sC5b9) and intact components or regulators (C1q, C2, C3, C4, C5, FD, FP, FH, FI). The specificity of each measurement was assessed by using complement proteins depleted sera and plasma collected from patients with complement deficiencies. Normal values distribution was estimated using 124 plasma samples from healthy donors and complement activation profile was assessed in plasma collected from 31 patients with various complement-mediated disorders.

RESULTS

We observed good inter-assay variation. All tested protein deficiencies were accurately detected. We established assay-specific reference values for each analyte. Except for C3, C4 and C4a, the majority of the measurements were in good agreement with references methods or published data.

CONCLUSION

Our study substantiates the utility of the Complement Multiplex assay as a tool for measuring complement activation and deficiencies. Quantifying complement cleavage fragments in patients exhibiting classical or alternative pathway activation allowed evaluating the activation state of the whole cascade.

Recommendations for the individualised management of atypical hemolytic uremic syndrome in adults

Background

Despite significant advances in therapeutic management of atypical hemolytic uremic syndrome (aHUS), guidelines are not timely updated and achieving a consensus on management recommendations remains a topic of ongoing discussion.

Methods

A Scientific Committee with five experts was set up. A literature review was conducted and publications addressing the classification of aHUS, patient profiles and therapeutic approach were selected. Recommendations were proposed at an initial meeting, evaluated through an online questionnaire and validated during a second meeting.

Results

Patients with confirmed or clear suspicion of aHUS should be treated with C5 inhibitors within 24 h of the diagnosis or suspicion of aHUS. Treatment monitoring and the decision to interrupt treatment should be individualised according to the risk of relapse and each patient's evolution. aHUS with a genetic variant or associated with pregnancy should be treated for at least 6-12 months; de novo aHUS associated with kidney transplant until renal function is recovered and genetic variants are ruled out; aHUS associated with malignant hypertension until genetic variants are ruled out; aHUS associated with non-kidney transplant, autoimmune diseases, infection-or drug-induced until the thrombotic microangiopathy is resolved. Patients with a high risk of relapse should be treated for longer than 6-12 months.

Conclusion

These recommendations provides physicians who are not familiar with the disease with recommendations for the management of aHUS in adults. The experts who participated advocate early treatment, maintenance for at least 6-12 months and treatment interruption guided by genetic background, trigger factors, risk of relapse and evolution.

HUS with mutations in CFH and STEC infection treated with eculizumab in a 4-year-old girl

BACKGROUND

Hemolytic uremic syndrome secondary to Shiga-toxin-producing Escherichia coli infection (STEC-HUS) generally shows a favorable outcome. Few cases develop extra-renal complications, since neurological involvement is an important cause of morbidity and mortality. The role of complement in STEC-HUS has been recently highlighted, and the use of eculizumab in severe cases has been communicated. HUS results from environmental and genetic factors, but the simultaneous occurrence of STEC and complement mutations remains undetermined.

METHODS

A pediatric case with severe STEC-HUS carrying CFH mutations, with favorable response to eculizumab is analyzed.

RESULTS

STEC-HUS was diagnosed in a 4-year-old girl with classic HUS, including low C3. Peritoneal dialysis was started due to hypertension, oligoanuria, and pleural effusion. She evolved with generalized tonic-clonic seizures and required mechanical ventilation. MRI reported multiple supra- and infratentorial ischemic lesions with laminar/striatal cortical necrosis and leukoencephalopathy. After two eculizumab doses, a significative stabilization in diuresis, blood pressure, creatinine, and C3 was achieved. At the third week, episodes of massive digestive bleeding and a life-threatening condition required a colectomy thus preserving the ileocecal valve. Due to atypical evolution, a genetic study was considered, identifying two heterozygous variants (CFH S1191L/V1197A).

CONCLUSION

STEC-HUS in patients with a genetic predisposition has been previously reported, but the low frequency of occurrence makes it a rare disease. As in the present case, patients with atypical course might benefit from genetic analysis to evaluate early eculizumab initiation and to better understand its phenotype. A higher resolution version of the Graphical abstract is available as Supplementary information.

Exploratory Prognostic Biomarkers of Complement-Mediated Thrombotic Microangiopathy (CM-TMA) in Adults with Atypical Hemolytic Uremic Syndrome (aHUS): Analysis of a Phase III Study of Ravulizumab

BACKGROUND

Clinically validated biomarkers for monitoring of patients with complement-mediated thrombotic microangiopathy (CM-TMA) including atypical hemolytic uremic syndrome (aHUS) are unavailable. Improved characterization of biomarkers in patients with aHUS may inform treatment and monitoring for patients with CM-TMA.

METHODS

This analysis used data collected from 55/56 (98.2 %) adult patients with aHUS enrolled in the global Phase III study of ravulizumab (NCT02949128). Baseline (pre-treatment) patient serum, plasma and urine biomarker levels were compared with the maximum observed levels in normal donors and evaluated for associations with pre-treatment plasma exchange/infusion and dialysis status. Biomarkers were also assessed for associations with key clinical measures at baseline and with changes at 26 and 52 weeks from treatment initiation via linear regression analyses.

RESULTS

Complement-specific urine levels (factor Ba and sC5b-9) were elevated in >85 % of patients and are significantly associated with pre-treatment kidney dysfunction. Baseline levels of other evaluated biomarkers were elevated in >70 % of patients with aHUS, except for plasma sC5b-9 and serum sVCAM-1. Lower levels of urine complement markers at baseline are significantly associated with improvements in total urine protein and estimated glomerular filtration rate at 26 and 52 weeks of treatment. Clinical assessment of complement activation by a receiver operating characteristic analysis of Ba and sC5b-9 was more sensitive and specific in urine matrix than plasma.

CONCLUSION

This analysis identified a set of biomarkers that may show utility in the prognosis of CM-TMA, including their potential for measuring and predicting response to anti-C5 therapy. Further studies are required to enhance patient risk stratification and improve management of these vulnerable patients.

CLINICAL TRIALS REGISTRATION

NCT02949128, ClinicalTrials.gov.

Renal Thrombotic Microangiopathy: A Review

Thrombotic microangiopathy (TMA), a pathological lesion observed in a wide spectrum of diseases, is triggered by endothelial injury and/or dysfunction. Although TMA lesions are often accompanied by clinical features of microangiopathic hemolytic anemia, thrombocytopenia, and ischemic end-organ injury, renal-limited forms of TMA are not infrequently encountered in clinical practice. The presence of renal-limited manifestations can be diagnostically challenging, often delaying the initiation of targeted therapy. Prompt investigation and empirical treatment of TMA is warranted to reduce associated morbidity and mortality. Major advances have been made with respect to the pathophysiology of primary TMA entities, with the subsequent development of novel diagnostic tools and lifesaving therapies for diseases like thrombotic thrombocytopenic purpura and complement-mediated TMA. This article will review the clinical presentation and pathologic hallmarks of TMA involving the kidney, and the disease-specific mechanisms that contribute to the endothelial injury that characterizes TMA lesions. Diagnostic approach and both empirical and disease-specific treatment strategies will be discussed, along with the potential role for emerging targeted disease-specific therapies.

Diagnosis and treatment of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is characterized by thrombocytopenia, microangiopathic haemolytic anaemia and end organ damage. TMAs have varying underlying pathophysiology and can therefore present with an array of clinical presentations. Renal involvement is common as the kidney is particularly susceptible to the endothelial damage and microvascular occlusion. TMAs require rapid assessment, diagnosis, and commencement of appropriate treatment due to the high morbidity and mortality associated with them. Ground-breaking research into the pathogenesis of TMAs over the past 20 years has driven the successful development of targeted therapeutics revolutionizing patient outcomes. This review outlines the clinical presentations, pathogenesis, diagnostic tests and treatments for TMAs.

Device-Related Thrombotic Microangiopathy in an Elderly Patient With a History of Aortic Surgery

Thrombotic microangiopathy (TMA) is caused by several diseases, including infections, congenital and autoimmune diseases, and malignancies, usually requiring admission to intensive care. The primary pathophysiology of TMA is microvascular thrombosis, and its diagnosis is based on the presence of hemolysis, thrombocytopenia, schistocytes in a blood smear, and organ damage. Among secondary TMAs, device-related TMA could be difficult to diagnose if device implementation was performed years ago. We report the case of an 87-year-old woman with a chief complaint of dyspnea diagnosed with device-related TMA. In device-related TMA, thrombogenesis/thrombocytopenia is triggered by hemolysis/fragmented red blood cells. However, in other TMAs, thrombogenesis or thrombocytopenia is preceded by hemolysis and the presence of fragmented red blood cells. Thus, rapid plasma exchange is necessary to address TMA pathogenesis. TMA can be managed in a community hospital if the facility has access to plasma exchange. It is possible to treat complex TMAs even in community hospitals by carefully considering their pathophysiology. Additionally, improving the quality of general practice in community hospitals will allow for more effective diagnosis and treatment of TMAs.