Extra-renal manifestations of complement-mediated thrombotic microangiopathies

Risk factors of death or chronic renal replacement therapy requirements in patients with thrombotic microangiopathies without ADAMTS-13 deficiency

Thrombotic microangiopathy (TMA), characterized by microangiopathic hemolytic anemia, thrombocytopenia, and multisystem organ dysfunction, is a life-threatening disease. Patients with TMA who do not exhibit a severe ADAMTS-13 deficiency (defined as a disintegrin-like and metalloprotease with thrombospondin type 1 motif no. 13 activity ≥10%: TMA-13n) continue to experience elevated mortality rates. This study explores the prognostic indicators for augmented mortality risk or necessitating chronic renal replacement therapy (composite outcome: CO) in TMA-13n patients. We included 42 TMA-13n patients from January 2008 to May 2018. Median age of 41 years and 60% were female. At presentation, 62% required dialysis, and 57% warranted intensive care unit admission. CO was observed in 45% of patients, including a 9-patient mortality subset. Multivariate logistic regression revealed three independent prognostic factors for CO: early administration of eculizumab (median time from hospitalization to eculizumab initiation: 5 days, range 0-19 days; odds ratio [OR], 0.14; 95% confidence interval [CI], 0.02-0.94), presence of neuroradiological lesions (OR, 6.67; 95% CI, 1.12-39.80), and a PLASMIC score ≤4 (OR, 7.39; 95% CI, 1.18-46.11). In conclusion, TMA-13n patients exhibit a heightened risk of CO in the presence of low PLASMIC scores and neuroradiological lesions, while early eculizumab therapy was the only protective factor.

Differential contributions of the C5b-9 and C5a/C5aR pathways to microvascular and macrovascular thrombosis in complement-mediated thrombotic microangiopathy patients

To clarify the role of the C5a/C5aR (C5a receptor) and C5b-9 pathways in macrovascular thrombosis (MAT) and renal microthrombosis (MIT), 73 renal biopsy-proven complement-mediated thrombotic microangiopathy (C-TMA) patients were enrolled; 9 patients with pure MAT and 13 patients with pure MIT were selected for further study. Twenty-five external C-TMA patients were selected as the validation cohort. Plasma C5a and sC5b-9 (soluble C5b-9) levels were significantly higher in patients with MAT than in those with MIT (P = 0.008, P = 0.041, respectively). The mean optical density of C5aR1 in the kidney was significantly higher in MAT patients than in those with MIT (P < 0.001). Both urinary sC5b-9 levels (MIT: P < 0.001, MAT: P = 0.004) and renal deposition of C5b-9 (MIT: P < 0.001, MAT: P = 0.001) were significantly higher in C-TMA patients compared to normal control, but were similar between MAT and MIT groups. In the correlation analysis within 22C-TMA patients, urinary sC5b-9 levels and renal deposition of C5b-9 were positively correlated to renal MIT formation (P = 0.009 and P = 0.031, respectively). Furthermore, the renal citrullinated histone H3 (CitH3)- and neutrophil elastase (NE)-positive area ratios were both significantly higher in the MAT group than in the MIT group (P = 0.006 and P = 0.020, respectively). Therefore, the local C5b-9 and C5a/C5aR1 pathways might have differential contributions to MIT and MAT formation in the disease.

Long-term survival and renal outcomes of thrombotic microangiopathy in pregnancy: A retrospective cohort study

OBJECTIVE

Thrombotic microangiopathy (TMA) in pregnancy can rapidly progress, leading to severe morbidities. This study aimed to compare baseline demographics and clinical outcomes between pregnant women with and without TMA.

METHODS

Using the National Health Insurance Research Database, 207 patients with pregnancy-related TMA from January 1, 2006 to December 31, 2015 were enrolled. Their data were compared with a 1:4 propensity score-matched cohort of 828 pregnant women without TMA to evaluate mortality and end-stage renal disease (ESRD) risks. Cox proportional hazards models were used to estimate the adjusted hazard ratio and 95% confidence intervals.

RESULTS

A total of 1035 participants were included. The risks of mortality and ESRD were 4.46 and 5.97 times higher for the TMA cohort, respectively. Subgroup analysis revealed higher mortality and ESRD risks in patients with TMA aged >40 years with a history of hypertension, stroke, cancer, concomitant stroke, malignant hypertension, or gastroenterocolitis than in the matched cohort.

CONCLUSION

Pregnant patients with TMA, especially those older and with comorbidities and organ involvement, faced increased mortality and ESRD risks. Physicians should collaborate with obstetricians throughout the prenatal and postpartum periods for these patients.

HUS and TTP: traversing the disease and the age spectrum

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP) are rare diseases sharing a common pathological feature, thrombotic microangiopathy (TMA). TMA is characterized by microvascular thrombosis with consequent thrombocytopenia, microangiopathic hemolytic anemia and/or multiorgan dysfunction. In the past, the distinction between HUS and TTP was predominantly based on clinical grounds. However, clinical presentation of the two syndromes often overlaps and, the differential diagnosis is broad. Identification of underlying pathogenic mechanisms has enabled the classification of these syndromes on a molecular basis: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS or complement-mediated TMA (aHUS/CM-TMA) associated with genetic or acquired defects leading to dysregulation of the alternative pathway (AP) of complement; and TTP that results from a severe deficiency of the von Willebrand Factor (VWF)-cleaving protease, ADAMTS13. The etiology of TMA differs between pediatric and adult patients. Childhood TMA is chiefly caused by STEC-HUS, followed by CM-TMA and pneumococcal HUS (Sp-HUS). Rare conditions such as congenital TTP (cTTP), vitamin B12 metabolism defects, and coagulation disorders (diacylglycerol epsilon mutation) present as TMA chiefly in children under 2 years of age. In contrast secondary causes and acquired ADAMT13 deficiency are more common in adults. In adults, compared to children, diagnostic delays are more frequent due to the wide range of differential diagnoses. In this review we focus on the three major forms of TMA, STEC-HUS, aHUS and TTP, outlining the clinical presentation, diagnosis and management of the affected patients, to help highlight the salient features and the differences between adult and pediatric patients which are relevant for management.

Challenging Cases in Cerebrovascular Disease

Disorders involving the vascular system of the brain are numerous and sundry. Atherosclerotic thromboembolism of large vessels and lacunar infarctions of small vessel disease are well known. Brain infarction due to cardioembolism is common as well, and even more so when diligently sought. Rupture of intracranial blood vessels results in subarachnoid and intraparenchymal hemorrhage. We present four cases of stroke of uncommon cause and remind clinicians to be open minded to the many possible causes of stroke, in particular because early recognition and treatment is often critical. Case 1 discusses a patient with inflammatory cerebral amyloid angiopathy. The presentation, ability to recur, and current treatment considerations are reviewed. Case 2 discusses microangiopathic thrombotic angiopathy. Diagnosis and treatment are considered. An association with interferon therapy and the evolving terminology of this and related conditions are discussed. Case 3 discusses intracranial hemorrhage secondary to acute promyelocytic leukemia. Patients with acute leukemias require aggressive management of their coagulopathy, thrombocytopenia, and the disease itself. Finally, Case 4 discusses ischemic stroke due to a paradoxical embolism in the setting of a patent foramen ovale (PFO). Both medical and surgical management of a PFO for stroke prevention are considered.

Cerebral vascular injury in transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) and atypical hemolytic uremic syndrome (aHUS) are complement-mediated TMAs. The central nervous system (CNS) is the most common extrarenal organ affected by aHUS, and, despite mechanistic overlap between aHUS and TA-TMA, CNS involvement is rarely reported in TA-TMA, suggesting that CNS involvement in TA-TMA may be underdiagnosed and that these patients may benefit from complement blockers. In addition, there are no widely used histologic or radiologic criteria for the diagnosis of TMA in the brain. Thirteen recipients of pediatric hematopoietic cell transplants (HCTs) who had TA-TMA and who underwent autopsy were studied. Seven of 13 brains had vascular injury, and 2 had severe vascular injury. Neurologic symptoms correlated with severe vascular injury. Classic TMA histology was present and most often observed in the cerebellum, brainstem, and cerebral white matter. Abnormalities in similar anatomic regions were seen on imaging. Brain imaging findings related to TMA included hemorrhages, siderosis, and posterior reversible encephalopathy syndrome. We then studied 100 consecutive HCT recipients to identify differences in neurologic complications between patients with and those without TA-TMA. Patients with TA-TMA were significantly more likely to have a clinical concern for seizure, have an electroencephalogram performed, and develop altered mental status. In summary, our study confirms that TA-TMA involves the brains of recipients of HCT and is associated with an increased incidence of neurologic symptoms. Based on these findings, we propose that patients with low- or moderate-risk TA-TMA who develop neurologic complications should be considered for TA-TMA-directed therapy.

The endothelial glycocalyx in critical illness: A pediatric perspective

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The endothelial glycocalyx thins with age and cardiovascular comorbidities.

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Endothelial glycocalyx is affected by and integral to severe pediatric illnesses.

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Mechanistic insight into cause/effect of endothelial glycocalyx injury is paramount.

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Vascular glycocalyx damage in pediatric critical illness warrants further study.

The vascular endothelium is the interface between circulating blood and end organs and thus has a critical role in preserving organ function. The endothelium is lined by a glycan-rich glycocalyx that uniquely contributes to endothelial function through its regulation of leukocyte and platelet interactions with the vessel wall, vascular permeability, coagulation, and vasoreactivity. Degradation of the endothelial glycocalyx can thus promote vascular dysfunction, inflammation propagation, and organ injury. The endothelial glycocalyx and its role in vascular pathophysiology has gained increasing attention over the last decade. While studies characterizing vascular glycocalyx injury and its downstream consequences in a host of adult human diseases and in animal models has burgeoned, studies evaluating glycocalyx damage in pediatric diseases are relatively few. As children have unique physiology that differs from adults, significant knowledge gaps remain in our understanding of the causes and effects of endothelial glycocalyx disintegrity in pediatric critical illness. In this narrative literature overview, we offer a unique perspective on the role of the endothelial glycocalyx in pediatric critical illness, drawing from adult and preclinical data in addition to pediatric clinical experience to elucidate how marked derangement of the endothelial surface layer may contribute to aberrant vascular biology in children. By calling attention to this nascent field, we hope to increase research efforts to address important knowledge gaps in pediatric vascular biology that may inform the development of novel therapeutic strategies.

Persistently elevated complement alternative pathway biomarkers in COVID-19 correlate with hypoxemia and predict in-hospital mortality

Mechanisms underlying the SARS-CoV-2-triggered hyperacute thrombo-inflammatory response that causes multi-organ damage in coronavirus disease 2019 (COVID-19) are poorly understood. Several lines of evidence implicate overactivation of complement. To delineate the involvement of complement in COVID-19, we prospectively studied 25 ICU-hospitalized patients for up to 21 days. Complement biomarkers in patient sera and healthy controls were quantified by enzyme-linked immunosorbent assays. Correlations with respiratory function and mortality were analyzed. Activation of complement via the classical/lectin pathways was variably increased. Strikingly, all patients had increased activation of the alternative pathway (AP) with elevated levels of activation fragments, Ba and Bb. This was associated with a reduction of the AP negative regulator, factor (F) H. Correspondingly, terminal pathway biomarkers of complement activation, C5a and sC5b-9, were significantly elevated in all COVID-19 patient sera. C5a and AP constituents Ba and Bb, were significantly associated with hypoxemia. Ba and FD at the time of ICU admission were strong independent predictors of mortality in the following 30 days. Levels of all complement activation markers were sustained throughout the patients’ ICU stays, contrasting with the varying serum levels of IL-6, C-reactive protein, and ferritin. Severely ill COVID-19 patients have increased and persistent activation of complement, mediated strongly via the AP. Complement activation biomarkers may be valuable measures of severity of lung disease and the risk of mortality. Large-scale studies will reveal the relevance of these findings to thrombo-inflammation in acute and post-acute COVID-19.

Diagnostic Considerations in H1N1 Influenza-induced Thrombotic Microangiopathy

Influenza virus can trigger atypical hemolytic uremic syndrome and present with complement-driven thrombotic microangiopathy (TMA). When administered promptly, complement-blocking therapies can spare organ injury and be lifesaving. However, diagnosing TMA in the setting of a severe viral infection can be challenging, as a significant overlap of symptoms and disease complications exists. This is particularly true in influenza virus infections and more recently, Coronavirus disease 2019 (COVID-19) infections. We present a 16-year-old male with H1N1 influenza-induced atypical hemolytic uremic syndrome who quickly improved with complement-blocking therapy, highlighting an urgent need to include TMA in the differential diagnosis of severe viral infections.

Case Report: Atypical HUS Presenting With Acute Rhabdomyolysis Highlights the Need for Individualized Eculizumab Dosing

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is an ultra-rare orphan disease caused by dysregulated complement activation resulting in thrombotic microangiopathy. Although complement-mediated endothelial injury predominantly affects the renal microvasculature, extra-renal manifestations are present in a significant proportion of patients. While eculizumab has significantly improved the morbidity and mortality of this rare disease, optimizing therapeutic regimens of this highly expensive drug remains an active area of research in the treatment of aHUS.

CASE PRESENTATION

This report describes the case of a previously healthy 4 year-old male who presented with rhabdomyolysis preceding the development of aHUS with anuric kidney injury requiring dialysis. Clinical stabilization required increased and more frequent eculizumab doses compared with the standardized weight-based guidelines. In the maintenance phase of his disease, pharmacokinetic analysis indicated adequate eculizumab levels could be maintained with an individualized dosing regimen every 3 weeks, as opposed to standard 2 week dosing, confirmed in this patient over a 4 year follow up period. Cost analyses show that weight-based maintenance dosing costs $312,000 per year, while extending the dosing interval to every 3 weeks would cost $208,000, a savings of $104,000 per year, relative to the cost of $72,000 from more frequent eculizumab dosing during his initial hospitalization to suppress his acute disease.

CONCLUSION

This case exemplifies the potential of severe, multisystem involvement of aHUS presenting with extra-renal manifestations, including rhabdomyolysis as in this case, and highlights the possibility for improved clinical outcomes and higher value care with individualized eculizumab dosing in patients over the course of their disease.

Concurrent cytomegalovirus enteritis and atypical hemolytic uremic syndrome with gastrointestinal tract involvement: a case report

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by complement dysregulation that may involve the extra-renal system. Without appropriate prophylactic treatment, aHUS commonly recur after kidney transplantation (KT). In contrast, cytomegalovirus (CMV) infection is common in KT recipients and may affect various organ systems. Herein, we report a case of recurrent aHUS complicated by CMV enteritis. This 17-year-old KT recipient with aHUS having a CFH mutation was admitted to the hospital for gastric pain and vomiting. With worsening hemogram, recurrence of aHUS involving the gastrointestinal (GI) system was suspected. Upon treatment with anti-C5 antibody, the patient’s blood counts soon improved, but her GI symptoms did not. Esophagogastroduodenoscopy revealed multiple ulcers in the duodenum with pathologic findings consistent with aHUS and CMV enteritis; however, she did not have CMV antigenemia despite these findings. Treatment with ganciclovir resolved GI symptoms within 7 days. This case shows that recurrence of aHUS is often induced by intercurrent infection, and common infections after allograft transplantation, such as CMV, should always be suspected and confirmed for a proper treatment, particularly because CMV enteritis may not accompany CMV antigenemia.

The Use of Eculizumab in Tacrolimus-Induced Thrombotic Microangiopathy

Drug-induced thrombotic microangiopathy (DITMA) is a secondary cause of thrombotic microangiopathy and a potentially fatal inflammatory disease. DITMA has been attributed to a variety of drugs, particularly chemotherapeutic and immunosuppressive agents. Prompt diagnosis is critical for survival and treatment necessitates withdrawal of the offending drug; however, many cases require further treatment including plasmapheresis, immunosuppression, and anticoagulation. In this article, we report a cutaneous biopsy-proven case of tacrolimus-induced DITMA, which was successfully treated with eculizumab after failing the conventional standard of care.

Cerebral Microangiopathy in Two Dogs with Cutaneous and Renal Glomerular Vasculopathy

Cutaneous and renal glomerular vasculopathy (CRGV) is an emerging disease in the UK, but its aetiology remains unclear. It is considered a thrombotic microangiopathy (TMA) in which the kidney and skin are the most commonly affected organs. We now document two cases of CRGV with brain lesions, which may have accounted for neurological signs displayed by these animals. The histopathological brain lesions were similar to TMA lesions in humans with thrombotic thrombocytopaenic purpura (TTP) and complement-mediated haemolytic uraemic syndrome (CM-HUS), in which the neurological signs are more associated with TMA than with any systemic disease or electrolyte imbalance. Fibrinoid necrosis in brain arterioles and associated lesions in these dogs were similar to those in human CM-HUS, indicating that the alternative complement pathway may play an important role in the pathophysiology of CRGV.

Pregnancy-triggered atypical hemolytic uremic syndrome (aHUS): a Global aHUS Registry analysis

Background

Atypical hemolytic uremic syndrome (aHUS) is a rare disease in which uncontrolled terminal complement activation leads to systemic thrombotic microangiopathy (TMA). Pregnancy can trigger aHUS and, without complement inhibition, many women with pregnancy-triggered aHUS (p-aHUS) progress to end-stage renal disease (ESRD) with a high risk of morbidity. Owing to relatively small patient numbers, published characterizations of p-aHUS have been limited, thus the Global aHUS Registry (NCT01522183, April 2012) provides a unique opportunity to analyze data from a large single cohort of women with p-aHUS.

Methods

The demographics and clinical characteristics of women with p-aHUS (n = 51) were compared with those of women of childbearing age with aHUS and no identified trigger (non-p-aHUS, n = 397). Outcome evaluations, including renal survival according to time to ESRD, were compared for patients with and without eculizumab treatment (a complement C5 inhibitor) in both aHUS groups.

Results

Baseline demographics and clinical characteristics were broadly similar in both groups. The proportion of women with p-aHUS and non-p-aHUS with pathogenic variant(s) in complement genes and/or anti-complement factor H antibodies was similar (45% and 43%, respectively), as was the proportion with a family history of aHUS (12% and 13%, respectively). Eculizumab treatment led to significantly improved renal outcomes in women with aHUS, regardless of whether aHUS was triggered by pregnancy or not: adjusted hazard ratio for time to ESRD was 0.06 (p = 0.006) in the p-aHUS group and 0.20 (p < 0.0001) in the non-p-aHUS group.

Conclusion

Findings from this study support the characterization of p-aHUS as a complement-mediated TMA.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01025-x.

Retrospective and Systematic Analysis of Causes and Outcomes of Thrombotic Microangiopathies in Routine Clinical Practice: An 11-Year Study

Background: Thrombotic microangiopathies (TMAs) are highly suspected in patients showing mechanical hemolytic anemia, thrombocytopenia, and haptoglobin consumption. Primary [thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome] and secondary TMA are considered. Even if ADAMTS13 measurements and alternative complement pathway explorations have greatly improved the ability to identify primary TMA, their diagnosis remains difficult, and their frequency relative to that of secondary TMA is undetermined. The objectives of the present study were, therefore, to describe the etiologies, management, and the outcomes of patients presenting with TMA in real-life clinical practice.

Methods: We conducted a retrospective study between 01/01/2008 and 31/12/2018 that included all consecutive patients presenting with biological TMA syndrome at admission or developing during hospitalization. Patients were identified from the laboratory databases, and their medical files were reviewed to confirm TMA diagnosis, to determine etiology, and to analyze their therapeutic management and outcomes.

Results: During this period, 239 patients with a full TMA biological syndrome were identified, and the TMA diagnosis was finally confirmed in 216 (90.4%) after the cases were reviewed. Primary TMAs (thrombotic thrombocytopenic purpura or atypical hemolytic uremic syndrome) were diagnosed in 20 of 216 patients (9.3%). Typical HUS was diagnosed in eight patients (3.7%), and the most frequent secondary TMAs were HELLP syndrome (79/216, 36.6%) and active malignancies (30/219, 13.9%). ADAMTS13 measurements and alternative complement pathway analyses were performed in a minority of patients. Multiple factors identified as TMA triggers were present in most patients, in 55% of patients with primary TMA, vs. 44.7% of patients with secondary TMA (p = 0.377). Death occurred in 57 patients (23.4%) during follow-up, and dialysis was required in 51 patients (23.6%). Active malignancies [odds ratio (OR) 13.7], transplantation (OR 4.43), male sex (OR 2.89), and older age (OR 1.07) were significantly associated with death.

Conclusion: Secondary TMAs represent many TMA causes in patients presenting a full TMA biological syndrome during routine clinical practice. Multiple factors favoring TMA are present in about half of primary or secondary TMA. ADAMTS13 and complement pathway were poorly explored in our cohort. The risk of death is particularly high in patients with malignancies as compared with patients with other TMA.

Severe Acral Necrosis Complicating Thrombotic Microangiopathy in Two Toddlers

Acral ischemia/necrosis is one of the rarest but most dreadful complications of thrombotic microangiopathy in pediatric patients. It is more reported with thrombotic thrombocytopenic purpura than with hemolytic and uremic syndrome. Even with anticoagulant therapy, it is often irreversible, leading to amputation.

Early relapse rate determines further relapse risk: results of a 5-year follow-up study on pediatric CFH-Ab HUS

BACKGROUND

The complement factor H antibody (CFH-Ab)-associated hemolytic uremic syndrome (HUS) forms a distinct subgroup within the complement-mediated HUS disease spectrum. The autoimmune nature of this HUS subgroup implies the potential benefit of a targeted immunosuppressive therapy. Data on long-term outcome are scarce.

METHODS

This observational study evaluates the clinical outcome of 19 pediatric CFH-Ab HUS patients from disease onset until their 5-year follow-up.

RESULTS

All but one relapse occurred during the first 2 years, and patients who had no relapse within the first 6 months were relapse-free until the end of the observation period. Kidney function at disease onset determines long-term kidney function: all individuals with normal kidney function at disease onset had normal kidney function after 5 years, and all patients with reduced kidney function at onset had impaired kidney function at the last follow-up. Level of CFH-Ab titer at disease onset was not correlated with a higher risk of recurrences or worse long-term outcome after 5 years. Resolution of CFH-Ab titers after 5 years was common.

CONCLUSIONS

CFH-Ab HUS patients have a varied overall long-term course. Early relapses are common, making close surveillance during the first years essential, regardless of the initial CFH-Ab titer.

A US cost-minimization model comparing ravulizumab versus eculizumab for the treatment of atypical hemolytic uremic syndrome

AIMS

Ravulizumab, engineered from eculizumab, provides sustained C5 inhibition in atypical hemolytic uremic syndrome (aHUS) while reducing dosing frequency (every 8 vs 2 weeks, respectively). Treatment choice often carries significant financial implications. This study compared the economic consequences of ravulizumab and eculizumab for treating aHUS.

MATERIALS AND METHODS

A cost-minimization model compared direct medical costs for ravulizumab and eculizumab in treating aHUS, assuming equivalent efficacy and safety, and took a US payer perspective, a lifetime horizon, and a 3.0% cost discount rate. The base case modeled adult and pediatric treatment-naïve populations, with characteristics based on clinical trials, and treatment patterns (duration, discontinuation, re-initiation) derived from eculizumab studies with long-term follow-up. Treatment costs (2019 US$) were based on wholesale drug acquisition costs, Centers for Medicare & Medicaid fee schedules, and published disease management studies. Sensitivity analyses were conducted by adjusting relevant variables.

RESULTS

Ravulizumab provided lifetime per-patient cost reductions (discounted) of 32.4% and 35.5% vs eculizumab in adult and pediatric base cases, respectively. Total costs for ravulizumab vs eculizumab were $12,148,748 and $17,979,007, respectively, for adults, and $11,587,832 and $17,959,814, respectively, for children. Pre-discontinuation treatment contributed the largest proportion of total costs for ravulizumab (94.8% and 88.0%) and eculizumab (94.8% and 87.8%) in adults and children, respectively. Across sensitivity analyses, ravulizumab provided cost reductions vs eculizumab.

LIMITATIONS

The model included several typical assumptions. Base case patients with more severe stages of chronic kidney disease were assumed not to discontinue treatment, nor to experience an excess mortality risk in either treatment arm, which may not reflect real-world clinical observations. Additionally, rebates and discounts on medication acquisition or administration were not considered.

CONCLUSIONS

In US patients with aHUS, ravulizumab provided cost reductions of 32.4-35.5% vs eculizumab, with a reduced dosing frequency for ravulizumab. The magnitude of reductions was consistent across sensitivity analyses.

Is the COVID-19 thrombotic catastrophe complement-connected?

In December 2019, the world was introduced to a new betacoronavirus, referred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for its propensity to cause rapidly progressive lung damage, resulting in high death rates. As fast as the virus spread, it became evident that the novel coronavirus causes a multisystem disease (COVID-19) that may involve multiple organs and has a high risk of thrombosis associated with striking elevations in pro-inflammatory cytokines, D-dimer, and fibrinogen, but without disseminated intravascular coagulation. Postmortem studies have confirmed the high incidence of venous thromboembolism, but also notably revealed diffuse microvascular thrombi with endothelial swelling, consistent with a thrombotic microangiopathy, and inter-alveolar endothelial deposits of complement activation fragments. The clinicopathologic presentation of COVID-19 thus parallels that of other thrombotic diseases, such as atypical hemolytic uremic syndrome (aHUS), that are caused by dysregulation of the complement system. This raises the specter that many of the thrombotic complications arising from SARS-CoV-2 infections may be triggered and/or exacerbated by excess complement activation. This is of major potential clinical relevance, as currently available anti-complement therapies that are highly effective in protecting against thrombosis in aHUS, could be efficacious in COVID-19. In this review, we provide mounting evidence for complement participating in the pathophysiology underlying the thrombotic diathesis associated with pathogenic coronaviruses, including SARS-CoV-2. Based on current knowledge of complement, coagulation and the virus, we suggest lines of study to identify novel therapeutic targets and the rationale for clinical trials with currently available anti-complement agents for COVID-19.

Angiotensin-converting enzyme 2, the complement system, the kallikrein-kinin system, type-2 diabetes, interleukin-6, and their interactions regarding the complex COVID-19 pathophysiological crossroads

Because of the current COVID-19-pandemic, the world is currently being held hostage in various lockdowns. ACE2 facilitates SARS-CoV-2 cell-entry, and is at the very center of several pathophysiological pathways regarding the RAAS, CS, KKS, T2DM, and IL-6. Their interactions with severe COVID-19 complications (e.g. ARDS and thrombosis), and potential therapeutic targets for pharmacological intervention, will be reviewed.

A Case Report of Atypical Hemolytic Uremic Syndrome in a Two-Month-Old Infant With a Negative Reported Genetic Profile and Five-Year Follow-Up on Eculizumab

Atypical hemolytic uremic syndrome (aHUS) is a rare but life-threatening pediatric disease caused by uncontrolled activation of the alternative complement pathway related to genetic mutations and carries a worse prognosis. In the last decade, a monoclonal antibody against complement C5, eculizumab, has dramatically improved the disease outcomes. The complement mutations in aHUS are detected only in 60%-70% of cases in previous studies. We report a severe presentation of aHUS diagnosed in a two-month-old child who presented with seizures, renal failure with anuria, and microangiopathic hemolytic anemia and required peritoneal dialysis soon after admission. The patient was clinically diagnosed having aHUS and was started on eculizumab on day 4 of hospital admission. The genetic study for major known complement mutations causing aHUS was reported negative. He had a major episode of disease relapse associated with seizures four weeks after eculizumab therapy and required prolonged peritoneal dialysis over more than two months at the time of initial admission. He developed dilated cardiomyopathy and oro-motor dysfunction as complications of aHUS. At five-year follow-up, the patient has stage 3 chronic kidney disease (CKD), proteinuria, hypertension, and required G-tube for feeds. This report discussed the long-term outcome of an infant diagnosed with aHUS and tested negative for common complement mutations on eculizumab therapy. More research is needed to identify novel genes and antibodies contributing to aHUS. While the eculizumab is expensive, and the duration of treatment is not definite, the clinical severity of the disease, relapses, and presence of long-term renal complications are essential factors to decide treatment continuation.

Atypical Hemolytic Uremic Syndrome Presenting as Acute Heart Failure-A Rare Presentation: Diagnosis Supported by Skin Biopsy

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder of uncontrolled complement activation that manifests classically as anemia, thrombocytopenia, and renal failure, although extrarenal manifestations are observed in 20% of the patient most of which involving central nervous system, with relatively rare involvement of the heart. In this article, we report the case of a 24-year-old male with no history of heart disease presenting with acute systolic heart failure along with microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Given his presentation of thrombotic microangiopathy (TMA), along with laboratory results significant for low haptoglobin, platelets, hemoglobin, C3, C4, CH50, and normal ADAMTS13 levels, with no diarrhea and negative STEC polymerase chain reaction in stool, aHUS diagnosis was established with strong clinical suspicion, and immediate initiation of treatment was advised. Kidney biopsy to confirm diagnosis of aHUS was inadvisable because of thrombocytopenia, so the skin biopsy of a rash on his arm was done, which came to be consistent with thrombotic microangiopathy. Our case highlights a relatively rare association between aHUS and cardiac involvement, and the use of skin biopsy to support diagnosis of aHUS in patients who cannot undergo renal biopsy because of thrombocytopenia.

Renal and pulmonary thrombotic microangiopathy triggered by proteasome-inhibitor therapy in patient with smoldering myeloma: A renal biopsy and autopsy case report

RATIONALE

Thrombotic microangiopathy (TMA) is a group of clinical syndromes characterized by excessive platelet activation and endothelial injury that leads to acute or chronic microvascular obliteration by intimal mucoid and fibrous thickening, with or without associated thrombi. It frequently involves the kidney but may involve any organ or system at variable frequencies depending on the underlying etiology. Among its numerous causes, drug toxicities and complement regulation abnormalities stand out as some of the most common. A more recently described association is with monoclonal gammopathy. Lung involvement by TMA is infrequent, but has been described in Cobalamin C deficiency and post stem-cell transplantation TMA.

PATIENT CONCERNS

This is the case of a patient with smoldering myeloma who received proteasome-inhibitor therapy due to retinopathy and developed acute renal failure within one week of therapy initiation.

DIAGNOSES

A renal biopsy showed thrombotic microangiopathy. At the time, mild pulmonary hypertension was also noted and presumed to be idiopathic.

INTERVENTIONS

Given the known association of proteasome-inhibitor therapy with thrombotic microangiopathy, Bortezomib was discontinued and dialysis was initiated.

OUTCOMES

Drug withdrawal failed to prevent disease progression and development of end-stage renal disease, as well as severe pulmonary hypertension that eventually lead to the patient's death.

LESSONS

To our knowledge, this is the first reported case of pulmonary involvement by TMA associated with monoclonal gammopathy which appears to have been triggered by proteasome-inhibitor therapy. Clinicians should be aware of this possibility to allow for more prompt recognition of pulmonary hypertension as a potential manifestation of monoclonal gammopathy-associated TMA, especially in patients also receiving proteasome-inhibitors, so that treatment aiming to slow disease progression can be instituted.

Extra-renal manifestations of atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare and complex disease resulting from abnormal alternative complement activation with a wide range of clinical presentations. Extra-renal manifestations of aHUS can involve many organ systems, including the peripheral and central nervous, gastrointestinal, cardiovascular, integumentary, pulmonary, as well as the eye. While some of these extra-renal manifestations occur in the acute phase of aHUS, some can also occur as long-term sequelae of unopposed complement activation. Extra-renal symptoms are observed in approximately 20% of patients with aHUS, with the incidence of specific organ system complications ranging from a few case reports to 50% of described patients. Careful monitoring for extra-renal involvement is critical in patients with aHUS, as prompt evaluation and management may decrease the risk of high morbidity and mortality associated with aHUS.

Extra-renal manifestations of atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare and complex disease resulting from abnormal alternative complement activation with a wide range of clinical presentations. Extra-renal manifestations of aHUS can involve many organ systems, including the peripheral and central nervous, gastrointestinal, cardiovascular, integumentary, pulmonary, as well as the eye. While some of these extra-renal manifestations occur in the acute phase of aHUS, some can also occur as long-term sequelae of unopposed complement activation. Extra-renal symptoms are observed in approximately 20% of patients with aHUS, with the incidence of specific organ system complications ranging from a few case reports to 50% of described patients. Careful monitoring for extra-renal involvement is critical in patients with aHUS, as prompt evaluation and management may decrease the risk of high morbidity and mortality associated with aHUS.

Atypical hemolytic uremic syndrome: a syndrome in need of clarity

Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA) originally understood to be limited to renal and hematopoietic involvement. Whereas aberrations in complement regulatory proteins (CRPs), C3 or complement factor B (CFB) are detected in ∼60% of patients, a complement-derived pathogenesis that reflects dysregulation of the alternative pathway (AP) of complement activation is present in ∼90% of patients. aHUS remains a diagnosis of exclusion. The discovery of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) and its utility in the diagnosis of thrombotic thrombocytopenic purpura (TTP) has resulted in the appreciation that cases of aHUS have been inappropriately diagnosed as TTP. Thus there has been an evolving appreciation of clinical manifestations of aHUS that renders the appellation aHUS misleading. This article will review the pathogenesis and the evolving clinical presentations of aHUS, present a hypothesis that there can be a phenotypic expression of aHUS due to a complement storm in a disorder where direct endothelial damage occurs and discuss future areas of research to more clearly define the clinical spectrum and management of aHUS.

Seizure as the Presenting Symptom for Atypical Hemolytic Uremic Syndrome

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a complement-mediated disease manifesting in thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. It has a higher incidence of extrarenal manifestations, including central nervous system findings like seizure or stroke, pancreatitis, and cardiac manifestations.

CASE REPORT

We present a case of an unimmunized 14-month-old girl presenting with generalized seizure and ultimately diagnosed with aHUS. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: These atypical neurological symptoms can cause the diagnosis to be commonly missed in the emergency department. The etiology of approximately 60% of patients with aHUS can be attributed to genetic mutations in complement regulators including factor H, membrane cofactor protein, factor I, activator factor B, or C3. Although previously treated with plasma transfusion and immunosuppressants, eculizumab is a newer treatment that has been changing prognosis and management of aHUS, but it should be administered within 48 h of symptom onset for best efficacy.

Targeting Complement Pathways in Polytrauma- and Sepsis-Induced Multiple-Organ Dysfunction

Exposure to traumatic or infectious insults results in a rapid activation of the complement cascade as major fluid defense system of innate immunity. The complement system acts as a master alarm system during the molecular danger response after trauma and significantly contributes to the clearance of DAMPs and PAMPs. However, depending on the origin and extent of the damaged macro- and micro -milieu, the complement system can also be either excessively activated or inhibited. In both cases, this can lead to a maladaptive immune response and subsequent multiple cellular and organ dysfunction. The arsenal of complement-specific drugs offers promising strategies for various critical conditions after trauma, hemorrhagic shock, sepsis, and multiple organ failure. The imbalanced immune response needs to be detected in a rational and real-time manner before the translational therapeutic potential of these drugs can be fully utilized. Overall, the temporal-spatial complement response after tissue trauma and during sepsis remains somewhat enigmatic and demands a clinical triad: reliable tissue damage assessment, complement activation monitoring, and potent complement targeting to highly specific rebalance the fluid phase innate immune response.

A pediatric neurologic assessment score may drive the eculizumab-based treatment of Escherichia coli-related hemolytic uremic syndrome with neurological involvement

BACKGROUND

Thrombotic microangiopathy (TMA) is a clinical syndrome encompassing a large group of rare but severe disorders including thrombotic thrombocytopenic purpura (TTP) and both typical and atypical forms of hemolytic uremic syndrome (HUS). The key role of the complement system is well known in TTP and atypical HUS, but recent reports describe its involvement in the pathogenesis of HUS secondary to gastrointestinal infections due to Shiga toxin-producing Escherichia coli (STEC).

METHODS

TMA mainly affects the kidney, but extra-renal complications are frequently described. The involvement of the central nervous system (CNS) represents often a life-threatening condition and it can result in serious long-term disability in HUS patients who overcome the acute phase of illness. In the present study, we retrospectively analyzed a pediatric cohort of a single tertiary pediatric hospital in Southern Italy, in which this complication occurred in 12/54 children (22% of cases), of whom five with severe neurological involvement had been successfully treated with eculizumab.

RESULTS

The great clinical variability of brain injury in our cohort has led us to retrospectively build a "neurological score" useful to assess the clinical severity of neurologic involvement. Subjects with higher neurologic score due to the most severe CNS involvement resulted in the group of patients early treated with eculizumab, obtaining a good clinical response (four out five patients). In conclusion, the early treatment with eculizumab in children with severe neurological involvement during STEC-HUS was associated with complete regression of both acute kidney injury (AKI) and neurological lesions observed at magnetic resonance imaging (MRI).

CONCLUSIONS

A "neurological score" may be a useful tool to drive the early treatment of CNS complications in STEC-HUS with eculizumab, although future perspective controlled studies are urgently needed to validate this therapeutic approach.

Atypical Hemolytic-Uremic Syndrome: An Update on Pathophysiology, Diagnosis, and Treatment

Atypical hemolytic uremic syndrome (aHUS), a rare variant of thrombotic microangiopathy, is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. The condition is associated with poor clinical outcomes with high morbidity and mortality. Atypical HUS predominantly affects the kidneys but has the potential to cause multi-organ system dysfunction. This uncommon disorder is caused by a genetic abnormality in the complement alternative pathway resulting in over-activation of the complement system and formation of microvascular thrombi. Abnormalities of the complement pathway may be in the form of mutations in key complement genes or autoantibodies against specific complement factors. We discuss the pathophysiology, clinical manifestations, diagnosis, complications, and management of aHUS. We also review the efficacy and safety of the novel therapeutic agent, eculizumab, in aHUS, pregnancy-associated aHUS, and aHUS in renal transplant patients.

Gemcitabine-induced haemolytic uremic syndrome, although infrequent, can it be prevented: A case report and review of literature

Gemcitabine is an antineoplastic used to treat several malignancies including pancreatic cancer. Its toxicity profile is well known with myelotoxicity, increased vascular permeability and peripheral oedema as most frequent adverse events. However, several cases of acute renal failure have been reported and haemolytic uremic syndrome (HUS) seems to be the underlying process. The cause of HUS remains unknown but its consequences can be lethal. Therefore, a high grade of suspicion is crucial to diagnose it and promptly treat it. This hopefully will reduce its morbidity. HUS is characterized by progressive renal failure associated with microangiopathic haemolytic anaemia and thrombocytopenia. The primary event is damage to endothelial cells and thrombotic microangiopathy (TMA) is the histopathological lesion. TMA affects mainly renal microvasculature. However, some cases evolve with central nervous or cardiovascular systems involvement. We present here a case of gemcitabine-induced HUS, with renal and cardiovascular system affected at the time of diagnosis which to our knowledge this is the first time of such case to be reported.

An adult case of atypical hemolytic uremic syndrome presented with posterior reversible encephalopathy syndrome: Successful response to late-onset eculizumab treatment

Atypical hemolytic uremic syndrome is a rare and progressive disease caused by uncontrolled alternative complement activation. Dysregulatıon of the complement activation results in thrombotic microangiopathy and multiorgan damage. A 29-yearold woman who was admitted with complaints of vomiting and headache was detected to have acute renal failure with microangiopathic hemolytic anemia (MAHA). After the diagnosis of atypical hemolytic uremic syndrome (aHUS), she was treated with plasma exchange (PE) and hemodialysis (HD). She has experienced hypertensionrelated posterior reversible encephalopathy syndrome (PRES) at the second plasma exchange. She was initiated on eculizumab therapy because of no response to PE on the 34^th days. Her renal functions progressively improved with eculizumab treatment. Dependence on dialysis was over by the 4^th month. Dialysis free-serum Creatinine level was 2.2 mg/dL [glomerular filtration rate (e-GFR): 30 mL/min/1.73 m²] after 24 months.

Neurological involvement (PRES, etc.) is the most common extrarenal complication and a major cause of mortality and morbidity from aHUS. More importantly, we showed that renal recovery may be obtained following late-onset eculizumab treatment in patient with aHUS after a long dependence on hemodialysis.

Extra-Renal manifestations of atypical hemolytic uremic syndrome in children

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a chronic disease characterized by thrombotic microangiopathy and a high risk of end-stage kidney disease. Dysregulation and/or excessive activation of the complement system results in thrombotic microangiopathy. Interest in extrarenal manifestations of aHUS is increasing. This study aimed to determine the clinical characteristics of patients with extrarenal manifestations of aHUS in childhood.

METHODS

This study included 70 children with extrarenal manifestations of HUS from the national Turkish aHUS Registry. The demographics, clinical characteristics, genetic test results, all treatments, and renal/hematologic status of aHUS patients with extrarenal involvement were recorded.

RESULTS

The most common extrarenal manifestation was neurological system involvement (n = 46 [27.2%]), followed by gastrointestinal (n = 20 [11.8%]), cardiovascular (n = 12 [7%]), and respiratory (n = 12 [7%]) involvement. The patients with neurological involvement had a higher mortality rate and a lower estimated glomerular filtration rate (eGFR) than the other patients at last follow-up. Eculizumab (with or without plasma exchange/plasma infusion) treatment increased the renal and hematologic recovery rates.

CONCLUSIONS

The most common and serious extrarenal manifestation of aHUS is neurological involvement and treatment outcome findings presented herein are important to all relevant clinicians.

Atypical hemolytic uremic syndrome: Review of clinical presentation, diagnosis and management

Thrombotic microangiopathies (TMA) are a class of disorders characterized by microangiopathic hemolytic anemia, non-immune thrombocytopenia, and organ dysfunction. One type of TMA is atypical hemolytic uremic syndrome (aHUS) a disorder caused by hyper-activation of the alternative complement pathway due to over activation of C3 convertases and loss of complement regulatory mechanisms. The pathophysiological mechanism of aHUS involves increased continuous spontaneous hydrolysis of C3 to C3b which leads to tissue deposition of C3b, the membrane attack complex formation and subsequent tissue injury. The underlying susceptibility factors to aHUS include acquired autoantibodies or germline mutations in complement proteins or their regulators. Currently there are no clear diagnostic criteria for aHUS. Diagnosis involves ruling out other causes of TMA and incorporating complement serologic and genetic data. TPE has been used to treat aHUS; however, clinical improvement in these patents is far less than in patients with thrombotic thrombocytopenic purpura. Furthermore, there is a higher rate of progression to end stage renal disease with almost half of patients progressing despite TPE. For those, another option for treatment is eculizumab, a monoclonal antibody that blocks complement C5. Eculizumab has proven effective in aHUS and dramatically changed the prognosis of this syndrome. In this review the clinical presentation, diagnosis and management of aHUS are highlighted with three clinical cases.

Clinical and genetic predictors of atypical hemolytic uremic syndrome phenotype and outcome

Atypical hemolytic uremic syndrome (aHUS) is a rare, genetic, life-threatening disease. The Global aHUS Registry collects real-world data on the natural history of the disease. Here we characterize end-stage renal disease (ESRD)-free survival, the rate of thrombotic microangiopathy, organ involvement and the genetic background of 851 patients in the registry, prior to eculizumab treatment. A sex-specific difference was apparent according to age at initial disease onset as the ratio of males to females was 1.3:1 for childhood presentation and 1:2 for adult presentation. Complement Factor I and Membrane Cofactor Protein mutations were more common in patients with initial presentation as adults and children, respectively. Initial presentation in childhood significantly predicted ESRD risk (adjusted hazard ratio 0.55 [95% confidence interval 0.41-0.73], whereas sex, race, family history of aHUS, and time from initial presentation to diagnosis, did not. Patients with a Complement Factor H mutation had reduced ESRD-free survival, whereas Membrane Cofactor Protein mutation was associated with longer ESRD-free survival. Additionally extrarenal organ manifestations occur in 19%-38% of patients within six months of initial disease presentation (dependent on organ). Thus, our real-world results provide novel insights regarding phenotypic variables and genotypes on the clinical manifestation and progression of aHUS.

Hemolytic uremic syndrome with dual caution in an infant: cobalamin C defect and complement dysregulation successfully treated with eculizumab

BACKGROUND

Hemolytic uremic syndrome (HUS) is a clinical syndrome characterized by hemolytic anemia, thrombocytopenia, and acute kidney injury. Atypical hemolytic uremic syndrome (aHUS) is a devastating disease with significant mortality and high risk of progression to end-stage kidney disease. It is mostly caused by dysregulation of the alternative complement pathway. Cobalamin C (Cbl C) defect is a genetic disorder of cobalamin metabolism and is a rare cause of HUS.

CASE-DIAGNOSIS/TREATMENT

We present a 6-month-old male infant who was admitted to the pediatric intensive care unit (PICU) due to restlessness, severe hypertension, anemia, respiratory distress, and acute kidney injury. Metabolic screening revealed elevated plasma homocysteine levels, low methionine levels, and methylmalonic aciduria, and the patient was diagnosed as having HUS secondary to Cbl C defect. Additionally, complement factor H (CFH) and complement C3 levels were decreased. The infant was treated with betaine, hydroxycobalamin, and folic acid. After treatment, the homocysteine and methylmalonic acid levels were normalized but hemolysis and acute kidney failure persisted. He required continued renal replacement treatment (CRRT) and plasma exchange due to thrombotic microangiopathy (TMA). Therefore, we considered a second mechanism in the pathogenesis as complement dysregulation and gave eculizumab to the patient. After eculizumab treatment, the renal and hematologic indices improved and he was free of dialysis.

CONCLUSIONS

To the best of our knowledge, our patient is the first to have Cbl C defect-HUS accompanied by complement dysregulation, who responded well to eculizumab therapy.

The use of eculizumab in gemcitabine induced thrombotic microangiopathy

BACKGROUND

Thrombotic microangiopathy (TMA) secondary to gemcitabine therapy (GiTMA) is a very rare pathology that carries a poor prognosis, with nearly half of the cases progressing to end stage renal disease. GiTMA is most commonly associated with adenocarcinomas, most notably pancreatic cancers. The mainstay of management is withdrawal of the offending drug and supportive care. Plasmapheresis has a limited role and hemodialysis may help in the management of fluid overload secondary to renal failure. Furthermore, a C5 inhibitor, eculizumab, has been successfully used in the treatment of GiTMA.

CASE PRESENTATION

A 64-year-old Caucasian female with history of pancreatic adenocarcinoma on gemcitabine chemotherapy presented with signs and symptoms of fluid overload and was found to have abnormal kidney function. Her BP was 195/110 mmHg, serum creatinine 4.48 mg/dl, hemoglobin 8.2 g/dl, platelets 53 × 103/cmm, lactate dehydrogenase 540 IU/L, and was found to have schistocytes on blood film. A diagnosis of TMA secondary to gemcitabine therapy was suspected. Hemodialysis for volume overload and daily plasmapheresis were initiated. After six days of plasmapheresis, renal function did not improve. Further work up revealed ADAMTS 13 activity >15%, low C3, and stool culture and Shiga-toxin PCR were negative. Renal biopsy was consistent with TMA. Gemcitabine was discontinued, but renal function failed to improve and eculizumab therapy was considered due to suspicion of aHUS. Serum creatinine >2.26 mg/dl and a platelet count of >/= 30 × 109/L is highly suggestive of aHUS, while TTP is more likely when creatinine is <2.26 mg/dl and platelet count of <30 × 109/L. She received intravenous eculizumab for eight months, which resulted in significant improvement of renal function. Other markers of hemolysis, namely LDH and bilirubin, also rapidly improved following eculizumab therapy. Plasmapheresis and hemodialysis were discontinued after two and eight weeks of initiation respectively.

CONCLUSION

Chemotherapy induced TMA is very rare and requires a high index of clinical suspicion for timely diagnosis. Discontinuation of the offending drug and supportive care is the main stay of treatment; however, eculizumab has been shown to be beneficial in GiTMA. Further research is required to validate this approach.

Short- and Long-Term Renal Outcome of Hemolytic-Uremic Syndrome in Childhood

Introduction: Hemolytic-uremic syndrome (HUS) is a common cause for intrarenal acute kidney injury in childhood. More than 90% of HUS cases are associated with an infection by Shigatoxin-producing Escherichia coli (STEC) whereas the reminder comprises a heterogeneous group (here classified as Non-STEC-HUS). Renal impairment can persist in patients with HUS. This study presents data from four decades investigating the short- and long-term outcome of HUS in childhood. Materials and Methods: In a retrospective single-center-study clinical and laboratory data of the acute phase and of 1- to 10-year follow-up visits of children with HUS were analyzed. Results: 92 HUS-patients were identified from 1996 to 2014 (STEC-HUS-group: n = 76; Non-STEC-HUS-group: n = 16) and 220 HUS-patients between 1976 and 1995. STEC-HUS was increasingly caused by Non-O157 strains and mortality rate declined over the past decades (1.3 vs. 9.5%). Renal sequelae persisted more often in the group 1976-1995 (39.3%) than in the group 1996-2014 (28.3%), but more than 50% of all patients were lost to follow-up. Conclusion: Although renal outcome has improved over the investigated last decades, patients with HUS still face a high risk of permanent renal damage. These findings underline the importance of a consequent long-term follow-up in HUS-patients.

Differential diagnosis of thrombotic microangiopathy in nephrology

Background

The differential diagnosis of thrombotic microangiopathy (TMA) is complex however the rapid diagnosis of the underlying condition is vital to inform urgent treatment decisions. A survey was devised with the objective of understanding current practices across Europe and the Middle East, and of challenges when diagnosing the cause of TMA.

Methods

Over 450 clinicians, from 16 countries were invited to complete an online survey.

Results

Of 254 respondents, the majority were nephrologists, had >10 years’ experience in their specialty, and had diagnosed a patient with TMA. The triad of thrombocytopenia, haemolytic anaemia and acute kidney injury are the main diagnostic criteria used. Responses indicate that a differential diagnosis of TMA is usually made within 1–2 (53%) or 3–4 days (26%) of presentation. Similarly, therapy is usually initiated within the first 4 days (74%), however 13% report treatment initiation >1-week post-presentation. Extrarenal symptoms and a panoply of other conditions are considered when assessing the differential diagnosis of TMA. While 70 and 78% of respondents stated they always request complement protein levels and ADAMTS13 activity, respectively. Diagnostic considerations of paediatric and adult nephrologists varied. A greater proportion of paediatric than adult nephrologists consider extrarenal manifestations clinically related to a diagnosis of TMA; pulmonary (45% vs. 18%), gastrointestinal (67% vs. 50%), CNS (96% vs. 84%) and cardiovascular (54% vs. 42%), respectively. Variability in the availability of guidelines and extent of family history taken was also evident.

Conclusions

This survey reveals the variability of current practices and the need for increased urgency among physicians in the differential diagnosis of TMA, despite their experience. Above all, the survey highlights the need for international clinical guidelines to provide systematically developed recommendations for understanding the relevance of complement protein levels, complement abnormalities and ADAMTS13 testing, in making a differential diagnosis of TMA. Such clinical guidelines would enable physicians to make a more rapid and informed diagnosis of TMA, therefore initiate effective treatment earlier, with a consequent improvement in patient outcomes.

Electronic supplementary material

The online version of this article (doi: 10.1186/s12882-017-0727-y) contains supplementary material, which is available to authorized users.

Outcomes of patients with atypical haemolytic uraemic syndrome with native and transplanted kidneys treated with eculizumab: a pooled post hoc analysis

Atypical haemolytic uraemic syndrome (aHUS) often leads to end-stage renal disease (ESRD) and kidney transplantation; graft loss rates are high due to disease recurrence. A post hoc analysis of four prospective clinical trials in aHUS was performed to evaluate eculizumab, a terminal complement inhibitor, in patients with native or transplanted kidneys. The trials included 26-week treatment and extension periods. Dialysis, transplant and graft loss were evaluated. Study endpoints included complete thrombotic microangiopathy (TMA) response, TMA event-free status, haematologic and renal parameters and adverse events. Of 100 patients, 74 had native kidneys and 26 in the transplant subgroup had a collective history of 38 grafts. No patients lost grafts and only one with pre-existing ESRD received a transplant on treatment. Efficacy endpoints were achieved similarly in both subgroups. After 26 weeks, mean absolute estimated glomerular filtration rate increased from baseline to 61 and 37 ml/min/1.73 m² in native (n = 71; P < 0.0001) and transplanted kidney (n = 25; P = 0.0092) subgroups. Two patients (one/subgroup) developed meningococcal infections; both recovered, one continued therapy. Eculizumab was well tolerated. Eculizumab improved haematologic and renal outcomes in both subgroups. In patients with histories of multiple graft losses, eculizumab protected kidney function.

Expert Statements on the Standard of Care in Critically Ill Adult Patients With Atypical Hemolytic Uremic Syndrome

A typical hemolytic uremic syndrome (aHUS) presents similarly to thrombotic thrombocytopenic purpura (TTP) and other causes or conditions with thrombotic microangiopathy (TMA), such as disseminated intravascular coagulation or sepsis. Similarity in clinical presentation may hinder diagnosis and optimal treatment selection in the urgent setting in the ICU. However, there is currently no consensus on the diagnosis or treatment of aHUS for ICU specialists. This review aims to summarize available data on the diagnosis and treatment strategies of aHUS in the ICU to enhance the understanding of aHUS diagnosis and outcomes in patients managed in the ICU. To this end, a review of the recent literature (January 2009-March 2016) was performed to select the most relevant articles for ICU physicians. Based on the paucity of adult aHUS cases overall and within the ICU, no specific recommendations could be formally graded for the critical care setting. However, we recognize a core set of skills required by intensivists for diagnosing and managing patients with aHUS: recognizing thrombotic microangiopathies, differentiating aHUS from related conditions, recognizing involvement of other organ systems, understanding the pathophysiology of aHUS, knowing the diagnostic workup and relevant outcomes in critically ill patients with aHUS, and knowing the standard of care for patients with aHUS based on available data and guidelines. In conclusion, managing critically ill patients with aHUS requires basic skills that, in the absence of sufficient data from patients treated within the ICU, can be gleaned from an increasingly relevant literature outside the ICU. More data on critically ill patients with aHUS are needed to validate these conclusions within the ICU setting.

Potential influences of complement factor H in autoimmune inflammatory and thrombotic disorders

Complement system homeostasis is important for host self-protection and anti-microbial immune surveillance, and recent research indicates roles in tissue development and remodelling. Complement also appears to have several points of interaction with the blood coagulation system. Deficiency and altered function due to gene mutations and polymorphisms in complement effectors and regulators, including Factor H, have been associated with familial and sporadic autoimmune inflammatory - thrombotic disorders, in which autoantibodies play a part. These include systemic lupus erythematosus, rheumatoid arthritis, atypical haemolytic uremic syndrome, anti-phospholipid syndrome and age-related macular degeneration. Such diseases are generally complex - multigenic and heterogeneous in their symptoms and predisposition/susceptibility. They usually need to be triggered by vascular trauma, drugs or infection and non-complement genetic factors also play a part. Underlying events seem to include decline in peripheral regulatory T cells, dendritic cell, and B cell tolerance, associated with alterations in lymphoid organ microenvironment. Factor H is an abundant protein, synthesised in many cell types, and its reported binding to many different ligands, even if not of high affinity, may influence a large number of molecular interactions, together with the accepted role of Factor H within the complement system. Factor H is involved in mesenchymal stem cell mediated tolerance and also contributes to self-tolerance by augmenting iC3b production and opsonisation of apoptotic cells for their silent dendritic cell engulfment via complement receptor CR3, which mediates anti-inflammatory-tolerogenic effects in the apoptotic cell context. There may be co-operation with other phagocytic receptors, such as complement C1q receptors, and the Tim glycoprotein family, which specifically bind phosphatidylserine expressed on the apoptotic cell surface. Factor H is able to discriminate between self and nonself surfaces for self-protection and anti-microbe defence. Factor H, particularly as an abundant platelet protein, may also modulate blood coagulation, having an anti-thrombotic role. Here, we review a number of interaction pathways in coagulation and in immunity, together with associated diseases, and indicate where Factor H may be expected to exert an influence, based on reports of the diversity of ligands for Factor H.

Recovery of renal function after long-term dialysis and resolution of cardiomyopathy in a patient with aHUS receiving eculizumab

We present the case of a 18-month-old girl with renal and cardiac manifestations of atypical haemolytic uraemic syndrome (aHUS), and a novel complement factor H mutation. Transient haematological remission was achieved with intensive plasmapheresis, but cardiac function deteriorated and renal function was not restored. Initiation of eculizumab after 6 months of dialysis significantly improved organ function. At 43 months after presentation, haematological values had normalised and cardiac function had improved. Dialysis was discontinued after 10 months (the longest reported time in a patient with aHUS) and the estimated glomerular filtration rate had recovered to 70 mL/min/1.73 m(2). In conclusion, treatment of aHUS with eculizumab, even after long-term dialysis, can significantly improve renal function. Discontinuation of dialysis and resolution of cardiac function has implications on the potential recovery and treatment choice of such patients. Earlier initiation of eculizumab, however, might have prevented the irreversible renal sclerosis and cardiac dysfunction.

Case report of atypical hemolytic uremic syndrome with retinal arterial and venous occlusion treated with eculizumab

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by chronic, uncontrolled activation of the alternative complement pathway, leading to thrombotic microangiopathy. Renal impairment and progression to end-stage renal disease are common in untreated patients with aHUS, and extrarenal manifestations are being increasingly characterized in the literature. Ocular involvement remains rare in aHUS. This report describes a patient with aHUS with bilateral central retinal artery and vein occlusion, vitreous hemorrhage, and blindness in addition to renal impairment. The patient's hematologic and renal parameters and ocular manifestation improved following initiation of eculizumab therapy.

HUS and the case for complement

Hemolytic-uremic syndrome (HUS) is a thrombotic microangiopathy that is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. Excess complement activation underlies atypical HUS and is evident in Shiga toxin-induced HUS (STEC-HUS). This Spotlight focuses on new knowledge of the role of Escherichia coli-derived toxins and polyphosphate in modulating complement and coagulation, and how they affect disease progression and response to treatment. Such new insights may impact on current and future choices of therapies for STEC-HUS.

De novo tacrolimus-induced thrombotic microangiopathy in the early stage after renal transplantation successfully treated with conversion to everolimus

BACKGROUND

Calcineurin inhibitor (CNI)-induced thrombotic microangiopathy (TMA) is a rare complication after renal transplantation. It may be difficult to distinguish from CNI toxicity and acute antibody-mediated rejection (AMR). Its clinical presentation may vary from isolated localised forms up to catastrophic systemic presentations.

CASE

We report a case of tacrolimus-induced TMA soon after renal transplantation in an 11-year-old boy who received his second renal transplantation. His first graft was lost because of AMR. On day 12 after his second renal transplantation, his renal function started worsening and a kidney biopsy was performed, which showed histopathological signs of TMA. The diagnosis of tacrolimus-induced TMA was established after excluding AMR and other causes of de novo TMA. Genetic complement investigation disclosed two complement factor H risk polymorphisms as possible modifiers of TMA emergence. Treatment was based on replacing tacrolimus with everolimus, with a subsequent normalisation of renal function.

CONCLUSION

A prompt diagnosis of de novo TMA by early allograft biopsy is essential for the allograft outcome and genetic investigations for possible complement abnormalities are reasonable, not only for patients with a systemic aspect of their post-transplant TMA. Replacing tacrolimus with everolimus effectively controlled the TMA and stabilised renal function in our patient.