Guideline for the investigation and initial therapy of diarrhea-negative hemolytic uremic syndrome

Atypical HUS: time to take stock of current guidelines and outcome measures?

European guidelines for the assessment and management of atypical HUS were written in 2009. Since then our understanding of this group of diseases has advanced. Evidence is emerging that eculizumab, a monoclonal antibody inhibiting C5 activation, is effective, and potentially superior to current treatment with plasmapheresis. The evidence base for the benefits of plasmapheresis consists of case series and small reports. Before we embark on a change of management policy it is vital that we set up a system for genetic diagnosis, standardised protocols and a means to collect predetermined outcome measures, so that we do not make the same mistakes with assessment of the effectiveness of eculizumab as we did for plasmapheresis.

Complement disorders and hemolytic uremic syndrome

PURPOSE OF REVIEW

Complement mediated hemolytic uremic syndrome (aHUS) accounts for a significant proportion of non-shiga toxin HUS. The purpose of this review is to outline the pathophysiology, clinical features and therapeutic options for aHUS.

RECENT FINDINGS

In the last decade, strides have been made in identifying several new disease-causing mutations in complement-regulating proteins.

SUMMARY

Complement mediated HUS (aHUS) has a worse prognosis compared with shiga toxin mediated HUS, often resulting in end stage renal disease. Early identification of aHUS is crucial so that plasma therapy can be initiated. After renal transplantation, there is very high risk of disease recurrence and graft loss. Eculizumab and combined liver-kidney transplantation offer promise for improved prognosis.

Combined complement gene mutations in atypical hemolytic uremic syndrome influence clinical phenotype

Several abnormalities in complement genes reportedly contribute to atypical hemolytic uremic syndrome (aHUS), but incomplete penetrance suggests that additional factors are necessary for the disease to manifest. Here, we sought to describe genotype-phenotype correlations among patients with combined mutations, defined as mutations in more than one complement gene. We screened 795 patients with aHUS and identified single mutations in 41% and combined mutations in 3%. Only 8%-10% of patients with mutations in CFH, C3, or CFB had combined mutations, whereas approximately 25% of patients with mutations in MCP or CFI had combined mutations. The concomitant presence of CFH and MCP risk haplotypes significantly increased disease penetrance in combined mutated carriers, with 73% penetrance among carriers with two risk haplotypes compared with 36% penetrance among carriers with zero or one risk haplotype. Among patients with CFH or CFI mutations, the presence of mutations in other genes did not modify prognosis; in contrast, 50% of patients with combined MCP mutation developed end stage renal failure within 3 years from onset compared with 19% of patients with an isolated MCP mutation. Patients with combined mutations achieved remission with plasma treatment similar to patients with single mutations. Kidney transplant outcomes were worse, however, for patients with combined MCP mutation compared with an isolated MCP mutation. In summary, these data suggest that genotyping for the risk haplotypes in CFH and MCP may help predict the risk of developing aHUS in unaffected carriers of mutations. Furthermore, screening patients with aHUS for all known disease-associated genes may inform decisions about kidney transplantation.

Multifaceted hemolytic uremic syndrome in pediatrics

Hemolytic uremic syndromes can have devastating consequences in childhood. The common feature of a microangiopathic hemolytic anemia and thrombocytopenia associated with varying degrees of renal injury often creates diagnostic confusion. The inability to arrive at a definitive diagnosis quickly can lead to a delay in initiating renal-preserving and sometimes life-saving treatment. Currently, both the treatment plan and the prognosis vary substantially according to the presumed diagnosis. The availability of anti-complement therapy makes differentiating the cause of the hemolytic uremic syndrome particularly critical. Therefore, it is imperative that consideration be given to each of the possible syndromes at presentation in order to facilitate correct diagnosis and development of an appropriate treatment strategy for both the acute phase and for the long-term care of the patient.

Atypical hemolytic uremic syndrome: what is it, how is it diagnosed, and how is it treated?

Atypical hemolytic uremic syndrome (aHUS) is a rare syndrome of hemolysis, thrombocytopenia, and renal insufficiency. Genetic mutations in the alternate pathway of complement are well recognized as the cause in more than 60% of patients affected by this thrombotic microangiopathy. The identification of aHUS as a disease of the alternate pathway of complement enables directed therapeutic intervention both in the acute and chronic setting and may include one or all of the following: plasma therapy, complement blockade, and liver transplantation. Because aHUS shares many of the presenting characteristics of the other thrombotic microangiopathies, and confirmatory genetic results are not available at the time of presentation, the diagnosis relies heavily on the recognition of a clinical syndrome consistent with the diagnosis in the absence of signs of an alternate cause of thrombotic microangiopathy. Limited understanding of the epidemiology, genetics, and clinical features of aHUS has the potential to delay diagnosis and treatment. To advance our understanding, a more complete characterization of the unique phenotypical features of aHUS is needed. Further studies to identify additional genetic loci for aHUS and more robust biomarkers of both active and quiescent disease are required. Advances in these areas will undoubtedly improve the care of patients with aHUS.

Eculizumab for atypical hemolytic uremic syndrome recurrence in renal transplantation

Eculizumab (anti-C5) has been sporadically reported as an efficient therapy for atypical hemolytic uremic syndrome (aHUS). However, the lack of series precludes any firm conclusion about the optimal use of anti-C5 for preventing or treating aHUS posttransplant aHUS recurrence. We thoroughly studied 22 renal transplant recipients with aHUS who received off-label therapy with anti-C5, including 12 cases, which have not been reported yet. Nine patients, all carrying a complement genetic abnormality associated with a high risk of aHUS recurrence, received prophylactic anti-C5 therapy to prevent posttransplant recurrence. Eight of them had a successful recurrence-free posttransplant course and achieved a satisfactory graft function, while the remaining patient experienced early arterial thrombosis of the graft. Thirteen renal transplant recipients were given anti-C5 for posttransplant aHUS recurrence. A complete reversal of aHUS activity was obtained in all of them. Importantly, the delay of anti-C5 initiation after the onset of the aHUS episode inversely correlated with the degree of renal function improvement. Three patients in whom anti-C5 was subsequently stopped experienced a relapse. Altogether these data suggest that long-term eculizumab is highly effective for preventing and treating posttransplant aHUS recurrence. Our study also indicates that anti-C5 should be promptly started if a recurrence occurs.

Eculizumab therapy in a child with hemolytic uremic syndrome and CFI mutation

BACKGROUND

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in childhood. It usually occurs after a prodromal episode of diarrhea and it leads to significant morbidity and mortality during the acute phase. However, cases that start as diarrhea-positive HUS whose renal function fail to recover should be screened for genetic disorders of the complement system, which is called atypical HUS (aHUS).

CASE-DIAGNOSIS/TREATMENT

We herein report a 10-year-old girl, who initially came with bloody diarrhea and had features of HUS with delayed renal and hematological recovery despite plasma therapy. Eculizumab (600 mg/week) was initiated on day 15 for atypical presentation and later a complement factor I (CFI) mutation was detected. The girl recovered diuresis within 24 h and after the third eculizumab infusion, hemoglobin, platelet, and C3 levels normalized; renal function improved; and proteinuria completely disappeared in 2 weeks.

CONCLUSION

It is our belief that eculizumab can be the treatment of choice in children who have plasma exchange-refractory HUS with defective regulation of the alternative complement pathway.

Preservation of renal function in atypical hemolytic uremic syndrome by eculizumab: a case report

Genetic mutations in complement components are associated with the development of atypical hemolytic uremic syndrome (aHUS), a rare disease with high morbidity rate triggered by infections or unidentified factors. The uncontrolled activation of the alternative pathway of complement results in systemic endothelial damage leading to progressive development of renal failure. A previously healthy 8-month-old boy was referred to our hospital because of onset of fever, vomiting, and a single episode of nonbloody diarrhea. Acute kidney injury with preserved diuresis, hemolytic anemia, and thrombocytopenia were detected, and common protocols for management of HUS were followed without considerable improvement. The persistent low levels of complement component C3 led us to hypothesize the occurrence of aHUS. In fact, the child carried a specific mutation in complement factor H (Cfh; nonsense mutation in 3514G>T, serum levels of Cfh 138 mg/L, normal range 350-750). Given the lack of response to therapy and the occurrence of kidney failure requiring dialysis, we used eculizumab as rescue therapy, a monoclonal humanized antibody against the complement component C5. One week from the first administration, we observed a significant improvement of all clinical and laboratory parameters with complete recovery from hemodialysis, even in the presence of systemic infections. Our case report shows that complement inhibiting treatment allows the preservation of renal function and avoids disease relapses during systemic infections.

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 individual's 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.

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

Atypical hemolytic uremic syndrome (HUS) refers to the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury in the absence of Shiga toxin-producing Escherichia coli exposure or Streptococcus pneumoniae infection. Currently, approximately 50 % of the atypical cases have demonstrable mutations in complement regulatory proteins. Historically, the diagnosis of atypical HUS portends a poor prognosis with a high rate of disease recurrence, progression to end-stage renal disease, and death. However, it is now evident that atypical HUS actually encompasses a heterogeneous group of disorders, and there are reports suggesting that some cases of atypical HUS have a favorable prognosis, similar to that of diarrhea-associated disease. We present three patients with the atypical HUS phenotype who had complete renal recovery and no disease recurrence. We believe it is important to distinguish those cases of atypical HUS associated with disorders of complement regulatory proteins from other idiopathic causes of nondiarrheal HUS given the implications for prognosis and treatment.

CONCLUSION

Given the heterogeneous nature and variable prognosis of atypical HUS, treatment should be carefully considered prior to the use of long-term plasma therapy and/or eculizumab.

Thrombotic microangiopathy and associated renal disorders

Thrombotic microangiopathy (TMA) is a pathological process involving thrombocytopenia, microangiopathic haemolytic anaemia and microvascular occlusion. TMA is common to haemolytic uraemic syndrome (HUS) associated with shiga toxin or invasive pneumococcal infection, atypical HUS (aHUS), thrombotic thrombocytopenic purpura (TTP) and other disorders including malignant hypertension. HUS complicating infection with shiga toxin-producing Escherichia coli (STEC) is a significant cause of acute renal failure in children worldwide, occurring sporadically or in epidemics. Studies in aHUS have revealed genetic and acquired factors leading to dysregulation of the alternative complement pathway. TTP has been linked to reduced activity of the ADAMTS13 cleaving protease (typically with an autoantibody to ADAMTS13) with consequent disruption of von Willebrand factor multimer processing. However, the convergence of pathogenic pathways and clinical overlap create diagnostic uncertainty, especially at initial presentation. Furthermore, recent developments are challenging established management protocols. This review addresses the current understanding of molecular mechanisms underlying TMA, relating these to clinical presentation with an emphasis on renal manifestations. A diagnostic and therapeutic approach is presented, based on international guidelines, disease registries and published trials. Early treatment remains largely empirical, consisting of plasma replacement/exchange with the exception of childhood STEC-HUS or pneumococcal sepsis. Emerging therapies such as the complement C5 inhibitor eculizumab for aHUS and rituximab for TTP are discussed, as is renal transplantation for those patients who become dialysis-dependent as a result of aHUS.

Invasive pneumococcal pneumonia is the major cause of paediatric haemolytic-uraemic syndrome in Taiwan

AIM

Streptococcus pneumoniae-associated haemolytic uraemic syndrome (SP-HUS) is a major concern of paediatric acute renal failure in Taiwan; it leads to significant morbidity and mortality during the acute phase and to long-term morbidity after an acute episode.

METHODS

Twenty children diagnosed with HUS between 1 May 1995, and 31 December 2008 was enrolled. Clinical variables related to laboratory data, organ involved, and outcomes were examined between patients with and without SP-HUS.

RESULTS

Thirteen of the 20 (13/20, 65%) patients required dialysis, nine (9/20, 45.0%) developed hepatic dysfunction, disseminated intravascular coagulation (DIC), gastrointestinal bleeding, and hypertension, respectively. They were the second most common extrarenal complication except empyema (11/20, 55%). Two (10%) died and seven (35%) of the survivors developed long-term renal morbidity. Twelve of the 20 patients (60%) were diagnosed with SP-HUS. Younger age, female children, higher white blood cell count, higher alanine transaminase, higher lactate dehydrogenase and high incidence of DIC were significantly common in SP-HUS cases. All SP-HUS cases were complicated with pleural effusion, empyema, or both. Positive Thomsen-Freidenreich antigen (T-Ag) activation was 83% sensitive and 100% specific for SP-HUS, and a positive direct Coombs' test was 58% sensitive and 100% specific.

CONCLUSION

Invasive pneumococcal infection is the most common cause of HUS in Taiwan. Positive T-Ag activation and a direct Coombs' test are rapid predictors of SP-HUS in children with invasive pneumonia.

Common variable immunodeficiency complicated with hemolytic uremic syndrome

Common variable immunodeficiency is a primary immunodeficiency disease characterized by reduced serum immunoglobulins and heterogeneous clinical features. Recurrent pyogenic infections of upper and lower respiratory tracts are the main clinical manifestations of common variable immunodeficiency. Hemolytic uremic syndrome is a multisystemic disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ ischemia due to platelet aggregation in the arterial microvasculature. This is one of the rare cases of patients diagnosed with common variable immunodeficiency, which was complicated by hemolytic uremic syndrome.

Tandem plasma-exchange and haemodialysis in a paediatric dialysis unit

BACKGROUND

The simultaneous use of plasma-exchange (PE) and haemodialysis (HD), known as tandem PE and HD (TPH), may be an additional resource for treating patients who need both therapies at the same time. However, little experience is reported in the paediatric setting.

CASE-DIAGNOSIS/TREATMENT

We retrospectively reviewed the TPH sessions performed in the last 5 years in our unit. Thirty-nine TPH treatments in eight pediatric patients were traced. The median age of the patients was 10.5 (range 5.1-19.2) years, and median weight was 27.6 (range 14.7-66.2) kg. Indications for TPH were atypical haemolytic uremic syndrome due to factor H or factor I dysregulation, or to a not yet defined abnormality, in most of the sessions (34/39 sessions). The remaining five sessions were performed for vasculitis, focal segmental glomerulosclerosis and hyperimmunization in a patient waiting for kidney transplant. In all treatments, TPH was completed and reached the desired ultrafiltration and substitution volumes; the duration of PE was shorter than that of HD. No significant adverse events were observed.

CONCLUSIONS

In those rare patients who require both PE and HD, TPH can improve their quality of life by reducing the time spent in extracorporeal circulation. This tandem treatment is safe and well-tolerated, even in subjects of relatively small body size.

Eculizumab in atypical haemolytic-uraemic syndrome allows cessation of plasma exchange and dialysis

Disorders in complement regulation are a major cause of atypical haemolytic-uraemic syndrome (aHUS). Eculizumab, a monoclonal antibody targeting complement C5 and blocking the terminal complement cascade, should theoretically be useful in this disease, particularly when associated with specific complement pathway anomalies such as Factor H deficiency. Eculizumab is emerging as an effective treatment for post-transplant aHUS recurrence and may have a role in treating de novo aHUS, halting the haemolytic process. In this case report, we describe the fourth case of aHUS treated with eculizumab. In our patient, with a known complement Factor H mutation, not only has the disease process become quiescent but also this therapy has led to significantly improved renal function so that dialysis is no longer necessary.

Management of hemolytic uremic syndrome

2011 has been a special year for hemolytic uremic syndrome (HUS): on the one hand, the dramatic epidemic of Shiga toxin producing E. coli -associated HUS in Germany brought the disease to the attention of the general population, on the other hand it has been the year when eculizumab, the first complement blocker available for clinical practice, was demonstrated as the potential new standard of care for atypical HUS. Here we review the therapeutic options presently available for the various forms of hemolytic uremic syndrome and show how recent knowledge has changed the therapeutic approach and prognosis of atypical HUS.

Therapeutic apheresis in children: special considerations

The provision of therapeutic apheresis to children is a technically challenging procedure, requiring trained personnel and an understanding of the disease processes that leads to the need for apheresis. Most apheresis protocols are derived from studies in adult patients, even though most studies are of limited sample size. The focus of this review is to highlight the disease processes commonly treated with therapeutic apheresis in children, and to address the technical considerations pertinent to the provision of safe and effective apheresis in the pediatric setting.

Pneumococcal disease manifestation in children before and after vaccination: what's new?

Pneumococcal infections remain a relevant cause of morbidity and mortality in children, especially in countries where vaccination has not been introduced. In contrast to the common belief by many pediatricians, the most important pneumococcal infections are of the respiratory tract and not invasive diseases. The recent pandemic of the H1N1 virus prompted studies to better understand the interaction between the influenza virus, Streptococcus pneumoniae, and pneumonia outcomes. Radiological findings of bacteremic pneumonia have been well investigated and besides the typical alveolar consolidation, a broad spectrum of atypical patterns has been reported. Molecular techniques, such as real-time polymerase chain reaction (PCR), can improve the detection of S. pneumoniae in sterile fluids, mainly in regions where previous antibiotic therapy is a common practice. In the post vaccination era, new manifestations of pneumococcal invasive disease, such as hemolytic uremic syndrome, have increased in association with parapneumonic empyema. Moreover, serotypes not included in PCV7, particularly serotypes 1, 3, 5, 7F, and 19A, have been among the most common isolates in pneumococcal disease. In Latin America, pneumococcal primary peritonitis has been described as an important clinical syndrome in a growing proportion of patients, mainly in girls. The development of newer and more specific diagnostic markers to distinguish bacterial and viral pneumonia are urgently sought, and will be especially pertinent after the introduction of pneumococcal conjugate vaccines with expanded serotypes. Such markers would minimize inappropriate diagnosis of false positive cases and treatment with antibacterial agents, while increasing positive predictive values for diagnosis of bacterial pneumonia. The extension of serotype coverage with the new conjugate vaccines is promising for pneumococcal infections and coverage against antibiotic-resistant strains.

Atypical hemolytic uremic syndrome in children: complement mutations and clinical characteristics

BACKGROUND

Mutations in complement factor H (CFH), factor I (CFI), factor B (CFB), thrombomodulin (THBD), C3 and membrane cofactor protein (MCP), and autoantibodies against factor H (αFH) with or without a homozygous deletion in CFH-related protein 1 and 3 (∆CFHR1/3) predispose development of atypical hemolytic uremic syndrome (aHUS).

METHODS

Different mutations in genes encoding complement proteins in 45 pediatric aHUS patients were retrospectively linked with clinical features, treatment, and outcome.

RESULTS

In 47% of the study participants, potentially pathogenic genetic anomalies were found (5xCFH, 4xMCP, and 4xC3, 3xCFI, 2xCFB, 6xαFH, of which five had ∆CFHR1/3); four patients carried combined genetic defects or a mutation, together with αFH. In the majority (87%), disease onset was preceeded by a triggering event; in 25% of cases diarrhea was the presenting symptom. More than 50% had normal serum C3 levels at presentation. Relapses were seen in half of the patients, and there was renal graft failure in all except one case following transplant.

CONCLUSIONS

Performing adequate DNA analysis is essential for treatment and positive outcome in children with aHUS. The impact of intensive initial therapy and renal replacement therapy, as well as the high risk of recurrence of aHUS in renal transplant, warrants further understanding of the pathogenesis, which will lead to better treatment options.

Eculizumab in the treatment of atypical hemolytic uremic syndrome in infants

A 28-day-old male newborn weighing 3.6 kg was given a diagnosis of atypical hemolytic-uremic syndrome, new-onset thrombotic microangiopathy (TMA; hemoglobin, 7.7 g/dL; schistocytes, 9%), thrombocytopenia (platelets, 49 × 10(3)/μL [49 × 10(9)/L]), and acute kidney failure (serum creatinine, 1.13 mg/dL [99.8 μmol/L], corresponding to estimated glomerular filtration rate [eGFR] of 15 mL/min/1.73 m(2) [0.25 mL/s/1.73 m(2)]). Repeated high-volume plasma infusions were ineffective. Plasma exchange was attempted, but not tolerated. The patient required mechanical ventilation and continuous renal replacement therapy. He developed multiple intestinal perforations and leg skin necrosis due to systemic TMA. A low C3 level (36 mg/dL) suggested complement activation. Eculizumab, 300 mg, was administered, and within 48 hours the patient recovered from acute kidney failure, with complete hematologic remission 2 weeks later. The infant, 14 months old at the time of writing, continues to receive eculizumab, 300 mg, every 3 weeks; he is free of disease activity and has a normal creatinine level of 0.2 mg/dL (17.68 μmol/L; corresponding to eGFR of 110 mL/min/1.73 m(2) [1.83 mL/s/1.73 m(2)]), but mild proteinuria (urinary protein-creatine ratio, 1 mg/g). Results of additional studies, including probing for cobalamin anomalies and measuring levels of ADAMTS13, complement factor H (CFH), factor I (CFI), and membrane cofactor protein (MCP), were unremarkable. Antibodies to CFH were undetectable, and mutation testing of the genes for CFH, CFI, and MCP gave negative results. Treatment with eculizumab was life saving, and with continued treatment, the patient showed sustained freedom from clinical TMA complications.

Plasma therapy for atypical haemolytic uraemic syndrome associated with heterozygous factor H mutations

Atypical haemolytic uraemic syndrome (aHUS) is frequently associated with mutations in the gene encoding complement factor H (CFH). The clinical response to plasma therapy in aHUS is variable. We present here our experience of plasma therapy in three aHUS patients with CFH mutations. Three children presented aged 4, 22 and 6 months (patients 1-3 respectively) in acute kidney injury requiring dialysis. Plasma therapy consisting of plasma filtration (patient 1) or plasma exchange (PEX; patients 2 and 3) was commenced early following presentation. This resulted in aHUS remission and cessation of dialysis after 2 weeks, 9 days and 2 weeks respectively. Relapses were common and associated with increasing the interval between PEX, but all responded to intensification of PEX therapy. Patient 1 recovered 50% of renal function after first presentation. She had four relapses and started peritoneal dialysis 41 months after presentation. Mutation screening of CFH showed a missense mutation (c.3546 G > T, p.Arg1182Ser) in exon 23. PEX in patient 2 was slowly tapered over 4 months to fortnightly sessions, but she relapsed when PEX was extended to every 4 weeks. Renal function remained normal 12 months post-presentation. Mutation screening of CFH showed a mutation in exon 23 (c.3590 T > C, p.Val1197Ala) and two additional sequence variants in exons 3 and 4. Patient 3 had two relapses associated with intercurrent illnesses concurrent with reducing PEX to weekly doses. Renal function was normal 5 months post-presentation. All three patients showed a good response to PEX with improved renal function both initially and following a relapse. Further research is necessary to determine the best maintenance strategy to delay or prevent end-stage kidney disease.

Eculizumab in atypical hemolytic uremic syndrome: long-term clinical course and histological findings

Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy associated with defective regulation of the alternative complement pathway. The prognosis for patients with aHUS is poor, and plasma exchange represents the first-line therapy. Eculizumab is a humanized monoclonal anti-C5 antibody that prevents the activation of the terminal complement pathway. Here, we report the case of a 9-year-old girl with frequent relapsing aHUS due to heterozygous factor H mutation who was initially treated with plasma exchange three times per week with 150% plasma exchange volume. This treatment frequently caused allergic reactions and school absences. Because any reduction in the frequency of plasma exchange immediately induced relapses of the aHUS, treatment with eculizumab, 600 mg every 2 weeks, was started and plasma exchange completely stopped. On this drug regimen the patient showed no evidence of disease activity during a period of more than 24 months. Renal function improved, proteinuria disappeared, the number of antihypertensive medications could be decreased, and the quality of life increased substantially. The inhibition of the terminal complement pathway by eculizumab was also confirmed by renal biopsy, which showed the absence of thrombotic microangiopathy 2 months after the initiation of eculizumab therapy. This case illustrates the long-term favorable outcome of aHUS with eculizumab treatment.

[Thrombophilic states in intensive care medicine]

Thrombophilic states are common in intensive care medicine. Generally, they are complications of serious underlying diseases or adverse effects of treatment measures. The attributive mortality rate for thrombophilic states is high. Early recognition and management are, thus, indispensable. In this review, important diagnostic and therapeutic aspects are briefly summarized. Leading symptoms and the context to the underlying disease or therapy, which result in a thrombophilic state, are the basics for a specific diagnostic workup. Almost all current treatment recommendations are based on expert opinion.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by the triad of mechanical hemolytic anemia, thrombocytopenia and renal impairment. Atypical HUS (aHUS) defines non Shiga-toxin-HUS and even if some authors include secondary aHUS due to Streptococcus pneumoniae or other causes, aHUS designates a primary disease due to a disorder in complement alternative pathway regulation. Atypical HUS represents 5 -10% of HUS in children, but the majority of HUS in adults. The incidence of complement-aHUS is not known precisely. However, more than 1000 aHUS patients investigated for complement abnormalities have been reported. Onset is from the neonatal period to the adult age. Most patients present with hemolytic anemia, thrombocytopenia and renal failure and 20% have extra renal manifestations. Two to 10% die and one third progress to end-stage renal failure at first episode. Half of patients have relapses. Mutations in the genes encoding complement regulatory proteins factor H, membrane cofactor protein (MCP), factor I or thrombomodulin have been demonstrated in 20-30%, 5-15%, 4-10% and 3-5% of patients respectively, and mutations in the genes of C3 convertase proteins, C3 and factor B, in 2-10% and 1-4%. In addition, 6-10% of patients have anti-factor H antibodies. Diagnosis of aHUS relies on 1) No associated disease 2) No criteria for Shigatoxin-HUS (stool culture and PCR for Shiga-toxins; serology for anti-lipopolysaccharides antibodies) 3) No criteria for thrombotic thrombocytopenic purpura (serum ADAMTS 13 activity > 10%). Investigation of the complement system is required (C3, C4, factor H and factor I plasma concentration, MCP expression on leukocytes and anti-factor H antibodies; genetic screening to identify risk factors). The disease is familial in approximately 20% of pedigrees, with an autosomal recessive or dominant mode of transmission. As penetrance of the disease is 50%, genetic counseling is difficult. Plasmatherapy has been first line treatment until presently, without unquestionable demonstration of efficiency. There is a high risk of post-transplant recurrence, except in MCP-HUS. Case reports and two phase II trials show an impressive efficacy of the complement C5 blocker eculizumab, suggesting it will be the next standard of care. Except for patients treated by intensive plasmatherapy or eculizumab, the worst prognosis is in factor H-HUS, as mortality can reach 20% and 50% of survivors do not recover renal function. Half of factor I-HUS progress to end-stage renal failure. Conversely, most patients with MCP-HUS have preserved renal function. Anti-factor H antibodies-HUS has favourable outcome if treated early.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by the triad of mechanical hemolytic anemia, thrombocytopenia and renal impairment. Atypical HUS (aHUS) defines non Shiga-toxin-HUS and even if some authors include secondary aHUS due to Streptococcus pneumoniae or other causes, aHUS designates a primary disease due to a disorder in complement alternative pathway regulation. Atypical HUS represents 5 -10% of HUS in children, but the majority of HUS in adults. The incidence of complement-aHUS is not known precisely. However, more than 1000 aHUS patients investigated for complement abnormalities have been reported. Onset is from the neonatal period to the adult age. Most patients present with hemolytic anemia, thrombocytopenia and renal failure and 20% have extra renal manifestations. Two to 10% die and one third progress to end-stage renal failure at first episode. Half of patients have relapses. Mutations in the genes encoding complement regulatory proteins factor H, membrane cofactor protein (MCP), factor I or thrombomodulin have been demonstrated in 20-30%, 5-15%, 4-10% and 3-5% of patients respectively, and mutations in the genes of C3 convertase proteins, C3 and factor B, in 2-10% and 1-4%. In addition, 6-10% of patients have anti-factor H antibodies. Diagnosis of aHUS relies on 1) No associated disease 2) No criteria for Shigatoxin-HUS (stool culture and PCR for Shiga-toxins; serology for anti-lipopolysaccharides antibodies) 3) No criteria for thrombotic thrombocytopenic purpura (serum ADAMTS 13 activity > 10%). Investigation of the complement system is required (C3, C4, factor H and factor I plasma concentration, MCP expression on leukocytes and anti-factor H antibodies; genetic screening to identify risk factors). The disease is familial in approximately 20% of pedigrees, with an autosomal recessive or dominant mode of transmission. As penetrance of the disease is 50%, genetic counseling is difficult. Plasmatherapy has been first line treatment until presently, without unquestionable demonstration of efficiency. There is a high risk of post-transplant recurrence, except in MCP-HUS. Case reports and two phase II trials show an impressive efficacy of the complement C5 blocker eculizumab, suggesting it will be the next standard of care. Except for patients treated by intensive plasmatherapy or eculizumab, the worst prognosis is in factor H-HUS, as mortality can reach 20% and 50% of survivors do not recover renal function. Half of factor I-HUS progress to end-stage renal failure. Conversely, most patients with MCP-HUS have preserved renal function. Anti-factor H antibodies-HUS has favourable outcome if treated early.

Genetics and CKD

The diagnosis of hereditary monogenic kidney diseases is frequently delayed, in part because of physicians' unfamiliarity with the relatively rare conditions or because of the late onset of symptoms in some patients. Molecular biology methods have clarified the underlying mutations in several types of CKD, and in the process have revealed previously unknown genes and pathogenetic pathways. Mutations affecting the integrity of the glomerular filtration barrier cause proteinuria or nephrotic syndrome; different types of Alport syndrome are caused by mutations in glomerular basement membrane type IV collagen; dysfunction of the primary cilium of tubule cells may lead to a variety of inherited progressive tubulointerstitial diseases; atypical hemolytic-uremic syndrome is frequently caused by inherited complement deficiencies; and progressive kidney injury develops in many inherited systemic or metabolic disorders. Some genetic diseases may not manifest until late childhood or adulthood. Accurate diagnosis is important for appropriate treatment, prognosis, genetic counseling, and possible renal transplantation.

Is complement a culprit in infection-induced forms of haemolytic uraemic syndrome?

Haemolytic uraemic syndrome (HUS) accounts for the most common cause of childhood acute renal failure. Characterized by the classical triad of a microangiopathic haemolytic anaemia, thrombocytopaenia and acute renal failure, HUS occurs as a result of Shiga-toxin producing microbes in 90% of cases. The remaining 10% of cases represent a heterogeneous subgroup in which inherited and acquired forms of complement dysregulation have been described in up to 60%. Emerging evidence suggests that microbes associated with HUS exhibit interaction with the complement system. With the advent of improved genetic diagnosis, it is likely that certain cases of infection-induced HUS may be attributed to underlying defects in complement components. This review summarises the interplay between complement and infection in the pathogenesis of HUS.

Microangiopathic disorders in pregnancy

Microangiopathic disorders present with thrombocytopenia, hemolytic anemia, and multiorgan damage. In pregnancy, these disorders present a challenge both diagnostically and therapeutically, with widely overlapping clinical scenarios and disparate treatments. Although rare, a clear understanding of these diseases is important because devastating maternal and fetal outcomes may ensue if there is misdiagnosis and improper treatment. Microangiopathic disorders presenting in pregnancy are thus best assessed and treated by both obstetric and hematology teams. As a better understanding of the pathophysiology underlying each of the disease processes is gained, new diagnostic testing and therapies will be available, which will lead to improved outcomes.

Successful simultaneous liver-kidney transplant in an adult with atypical hemolytic uremic syndrome associated with a mutation in complement factor H

Atypical hemolytic uremic syndrome was diagnosed in a 62-year-old man. Sequencing of the CFH gene, which encodes complement factor H, revealed a heterozygous adenine to guanine mutation at nucleotide 3550 of the complementary DNA, leading to a predicted substitution of alanine for threonine at amino acid position 1184 in the protein (c.3550A>G, p.Thr1184Ala). Three years later, he received a simultaneous liver-kidney transplant with plasmapheresis and intratransplant plasma infusion. The postoperative course was complicated by an anastomotic biliary stricture that was treated successfully using endoscopic stenting. One year later, he has excellent function of both transplants, emphasizing that simultaneous liver-kidney transplant is a valuable treatment option in the management of adult patients with atypical hemolytic uremic syndrome.

Pre-emptive eculizumab and plasmapheresis for renal transplant in atypical hemolytic uremic syndrome

The case of a 12-year-old with a hybrid CFH/CFHL1 gene and atypical hemolytic uremic syndrome (aHUS) that had previously developed native kidney and then renal allograft loss is reported. This case illustrates the relatively common occurrence of renal loss from the late presentation of aHUS. Also presented is a protocol for the pre-emptive use of eculizumab and plasmapheresis as part of a renal transplant plan for the treatment of aHUS in patients deemed at high risk for recurrent disease. This protocol was a result of a multidisciplinary approach including adult and pediatric nephrology, transplant surgery, transfusion medicine, and infectious disease specialists. This protocol and the justifications and components of it can function as a guideline for the treatment of a group of children that have waited in limbo for the first U.S. transplant to open the door to this type of definitive care for this devastating disease.

Efficacy of eculizumab in a patient with factor-H-associated atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare, chronic, life-threatening disease due to complement dysregulation. The use of early-onset plasma therapy is recommended, but optimal long-term treatment regimen is not well defined. Eculizumab, a monoclonal humanized anti-C5 antibody, has shown success in patients with aHUS. We report a 7-year-old girl with aHUS associated with factor H mutations successfully treated with eculizumab. Weekly plasma infusion (PI) of 25-30 ml/kg with short-term intensified PI during aHUS exacerbations was effective for 4.3 years. Progressive mild renal failure (stage 2) was attributed to chronic glomerular lesions. Subsequently, she exhibited aHUS exacerbation unresponsive to intensified PI. Eculizumab was initiated at 600 mg, resulting in immediate and complete inhibition of terminal complement activation. During the week following treatment, we observed a complete reversal of aHUS activity. She has been receiving 600 mg eculizumab every 2 weeks for the last 12 months. She had no aHUS exacerbation, and serum creatinine level returned to normal. In this patient, eculizumab led to control of PI-resistant aHUS exacerbation and chronic microangiopathic hemolytic activity. Clinical trials are ongoing to assess the safety and efficacy of this drug in the management of aHUS.

Advances in our understanding of the pathogenesis of glomerular thrombotic microangiopathy

Glomerular thrombotic microangiopathy is a hallmark feature of haemolytic uraemic syndrome, the leading cause of acute renal failure in childhood. This paper is a review of the different mechanistic pathways that lead to this histological picture in the kidney. It will focus on atypical HUS and complement dysregulation, but will also highlight some other recent advances in our understanding of this condition, including the potential role of the molecule vascular endothelial growth factor-A (VEGF-A).

Evaluation and management of critically ill children with acute kidney injury

PURPOSE OF REVIEW

This review will highlight recent studies on the diagnosis of acute kidney injury (AKI), review the differential diagnosis, highlight the importance of cumulative fluid overload and provide key management strategies for the pediatric patient with AKI.

RECENT FINDINGS

Over the last decade, serum creatinine-based categorical definitions of AKI have been accepted, which allow detection earlier in the disease process. Evidence-based modifications of these definitions have occurred. Fluid overload portends poor outcomes in critically ill patients. Significant improvements in our understanding of the pathophysiology of glomerular/vascular causes of AKI have occurred.

SUMMARY

Categorical definitions of AKI have shown that higher AKI portends poor outcomes even with adjustment for severity of illness and other confounders. Cumulative fluid overload independently predicts poor outcomes. Strategies to prevent and/or treat fluid overload are likely to improve outcomes.

[Atypical hemolytic-uremic syndrome related to abnormalities within the complement system]

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy (TMA) disorder characterised by the association of haemolytic anaemia, thrombocytopenia and acute renal failure. Atypical forms (non-shigatoxin related forms) may be familial or sporadic, frequently with relapses and most of them lead to end stage renal failure. During the last years, different groups have demonstrated genetic predisposition to atypical HUS (aHUS) involving five genes encoding for complement components which play a role in the activation or control of the alternative pathway: encoding factor H (CFH), accounting for 30% of aHUS; CD46 (encoding membrane cofactor protein [MCP]) accounting for approximately 10% of aHUS; CFI (encoding factor I) accounting for an estimated 5-15% of patients; C3 (encoding C3) accounting for approximately 10% of aHUS; and rarely CFB (encoding factor B). Predisposition to aHUS is inherited with incomplete penetrance. It is admitted that mutations confer a predisposition to develop aHUS rather than directly causing the disease and that a second event (genetic or environmental) is required for disease manifestation. HUS onset follows a triggering event in most cases (frequently banal seasonal infection and pregnancy). Uncontrolled C3 convertase leads to increased deposition of C3b on vascular endothelium and participates to the prothrombotic state. The phenotype of aHUS is variable ranging from mild forms, with complete recovery of renal function to severe forms with end stage renal disease within the first year after the onset. Overall, the outcome is severe with a mortality rate of 10% and with more than 60% of patients on dialysis. The most severe prognosis was in the CFH mutation group. There is a high risk of recurrence of the disease after renal transplantation in patients with mutations in CFH, CFI, CFB and C3. Plasma therapy may allow complete haematological remission but frequently with persistent renal damage. Some patients are plasma resistant and some are plasma dependent. The recent progress in the determination of the susceptibility factors for aHUS, have allowed to propose new diagnostic tests including a molecular genetic testing and may permit to consider some new specific treatments in this disease (human plasma-derived CFH or complement inhibitors).

Alternative complement pathway assessment in patients with atypical HUS

The atypical Hemolytic Uremic Syndrome (aHUS) is a rare thrombotic microangiopathy leading to end stage renal disease in approximately 60% of patients. Over the last decade, a clear link has been demonstrated between this disease and defective complement regulation. The hallmark of the aHUS is the association with mutations in complement alternative pathway genes. Endothelial damage is related to complement dysregulation, but the exact mechanism is just starting to be elucidated. Screening for and characterization of mutations in the components of the C3 convertase (C3 and FB) or its regulators (FH, FI, MCP, and Thrombomodulin) or anti-FH antibodies has become an indispensable part of the disease's diagnostic. This review will initially summarize current knowledge on the understanding of complement activation and regulation, followed by a description on the genetic analysis as well as the methods used for complement protein quantification. Another part of this review will focus on the mechanisms of action of aHUS-associated mutations. We will emphasize on when and why some mutations lead to protein deficiency, while others result in - to dysfunctional but normally expressed proteins. Finally, we will discuss how the therapy of aHUS patients can be modified according to the functional consequences of each particular genetic defect.

Atypical hemolytic uremic syndrome, genetic basis, and clinical manifestations

Atypical hemolytic uremic syndrome (aHUS) is now well recognized to be a disease characterized by excessive complement activation in the microvasculature. In both the familial and sporadic forms, inherited and acquired abnormalities affecting components of the alternative complement pathway are found in ~ 60% of patients. These include mutations in the genes encoding both complement regulators (factor H, factor I, membrane cofactor protein, and thrombomodulin) and activators (factors B and C3) and autoantibodies against factor H. Multiple hits are necessary for the disease to manifest, including a trigger, mutations, and at-risk haplotypes in complement genes. The prognosis for aHUS is poor, with most patients developing end-stage renal failure. Renal transplantation in most patients also has a poor prognosis, with frequent loss of the allograft to recurrent disease. However, improving results with combined liver-kidney transplantation and the advent of complement inhibitors such as eculizumab offer hope that the prognosis for aHUS will improve in future years.

aHUS caused by complement dysregulation: new therapies on the horizon

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective complement regulation in over 50% of cases. Mutations have been identified in genes encoding both complement regulators [complement factor H (CFH), complement factor I (CFI), complement factor H-related proteins (CFHR), and membrane cofactor protein (MCP)], as well as complement activators [complement factor B (CFB) and C3]. More recently, mutations have also been identified in thrombomodulin (THBD), an anticoagulant glycoprotein that plays a role in the inactivation of C3a and C5a. Inhibitory autoantibodies to CFH account for an additional 5-10% of cases and can occur in isolation or in association with mutations in CFH, CFI, CFHR 1, 3, 4, and MCP. Plasma therapies are considered the mainstay of therapy in aHUS secondary to defective complement regulation and may be administered as plasma infusions or plasma exchange. However, in certain cases, despite initiation of plasma therapy, renal function continues to deteriorate with progression to end-stage renal disease and renal transplantation. Recently, eculizumab, a humanized monoclonal antibody against C5, has been described as an effective therapeutic strategy in the management of refractory aHUS that has failed to respond to plasma therapy. Clinical trials are now underway to further evaluate the efficacy of eculizumab in the management of both plasma-sensitive and plasma-resistant aHUS.

Genetics and complement in atypical HUS

Central to the pathogenesis of atypical hemolytic uremic syndrome (aHUS) is over-activation of the alternative pathway of complement. Following the initial discovery of mutations in the complement regulatory protein, factor H, mutations have been described in factor I, membrane cofactor protein and thrombomodulin, which also result in decreased complement regulation. Autoantibodies to factor H have also been reported to impair complement regulation in aHUS. More recently, gain of function mutations in the complement components C3 and Factor B have been seen. This review focuses on the genetic causes of aHUS, their functional consequences, and clinical effect.

Triggering of atypical hemolytic uremic syndrome by influenza A (H1N1)

We report a case of atypical hemolytic uremic syndrome (aHUS) triggered by influenza A (H1N1) in a 17-year-old boy with a mutation in the gene (CD46) encoding the transmembrane complement regulator membrane cofactor protein. The patient recovered completely following treatment with oseltamivir, plasma exchange, and hemodialysis. We describe the case and discuss this unusual association of diseases.