A case-based narrative review of pregnancy-associated atypical hemolytic uremic syndrome/complement-mediated thrombotic microangiopathy

Atypical hemolytic uremic syndrome is a complement-mediated thrombotic microangiopathy caused by uncontrolled activation of the alternative complement pathway in the setting of autoantibodies to or rare pathogenic genetic variants in complement proteins. Pregnancy may serve as a trigger and unmask atypical hemolytic uremic syndrome/complement-mediated thrombotic microangiopathy (aHUS/CM-TMA), which has severe, life-threatening consequences. It can be difficult to diagnose aHUS/CM-TMA in pregnancy due to overlapping clinical features with other thrombotic microangiopathy syndromes including hypertensive disorders of pregnancy. However, the distinction among thrombotic microangiopathy etiologies in pregnancy is important because each syndrome has specific disease management and treatment. In this narrative review, we discuss 2 cases to illustrate the diagnostic challenges and evolving approach in the management of pregnancy-associated aHUS/CM-TMA. The first case involves a 30-year-old woman presenting in the first trimester who was diagnosed with aHUS/CM-TMA and treated with eculizumab from 19 weeks' gestation. Genetic testing revealed a likely pathogenic variant in CFI. She successfully delivered a healthy infant at 30 weeks' gestation. In the second case, a 22-year-old woman developed severe postpartum HELLP syndrome, requiring hemodialysis. Her condition improved with supportive management, yet investigations assessing for aHUS/CM-TMA remained abnormal 6 months postpartum consistent with persistent complement activation but negative genetic testing. Through detailed case discussion describing tests assessing for placental health, fetal anatomy, complement activation, autoantibodies to complement regulatory proteins, and genetic testing for aHUS/CM-TMA, we describe how these results aided in the clinical diagnosis of pregnancy-associated aHUS/CM-TMA and assisted in guiding patient management, including the use of anticomplement therapy.

Case report: A family of atypical hemolytic uremic syndrome involving a CFH::CFHR1 fusion gene and CFHR3-1-4-2 gene duplication

Mutations in the complement factor H (CFH) gene are associated with complement dysregulation and the development of atypical hemolytic uremic syndrome (aHUS). Several fusion genes that result from genomic structural variation in the CFH and complement factor H-related (CFHR) gene regions have been identified in aHUS. However, one allele has both CFHR gene duplication and CFH::CFHR1 fusion gene have not been reported. An 8-month-old girl (proband) presented with aHUS and was treated with ravulizumab. Her paternal grandfather developed aHUS previously and her paternal great grandmother presented with anti-neutrophil cytoplasmic antibody-associated vasculitis and thrombotic microangiopathy (TMA). However, the proband's parents have no history of TMA. A genetic analysis revealed the presence of CFH::CFHR1 fusion gene and a CFHR3-1-4-2 gene duplication in the patient, her father, and her paternal grandfather. Although several fusion genes resulting from structural variations of the CFH-CFHR genes region have been identified, this is the first report of the combination of a CFH::CFHR1 fusion gene with CFHR gene duplication. Because the CFH-CFHR region is highly homologous, we hypothesized that CFHR gene duplication occurred. These findings indicate a novel pathogenic genomic structural variation associated with the development of aHUS.

Constipation and hemolytic uremic syndrome

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) classically presents with diarrhea. Absence of diarrheal prodrome increases suspicion for atypical HUS (aHUS). Inability to obtain a fecal specimen for culture or culture-independent testing limits the ability to differentiate STEC-HUS and aHUS.

CASE-DIAGNOSIS/TREATMENT

Our patient presented with abdominal pain and constipation, and evaluation of pallor led to a diagnosis of HUS. There was a complete absence of diarrhea during the disease course. Lack of fecal specimen for several days delayed testing for STEC. Treatment for atypical HUS was initiated with complement-blockade therapy. PCR-testing for Shiga toxin from fecal specimen later returned positive. Alternative complement-pathway testing did not identify a causative genetic variant or anti-Factor H antibody. A diagnosis of STEC-HUS was assigned, and complement-blockade therapy was stopped.

CONCLUSION

Diagnosis of aHUS remains a diagnosis of exclusion, whereby other causes of HUS are eliminated with reasonable certainty. Exclusion of STEC is necessary and relies on testing availability and recognition of testing limitations. Diarrhea-negative STEC-HUS remains a minority of cases, and future research is needed to explore the clinical characteristics of these patients.

Management of pediatric hemolytic uremic syndrome

Classical clinical triad of hemolytic uremic syndrome (HUS) is microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury associated with endothelial cell injury. Several situations, including infections, medications, malignancies, and transplantation can trigger endothelial damage. On the HUS spectrum, atypical hemolytic uremic syndrome (aHUS) deserves special attention in pediatric patients, as it can cause endstage kidney disease and mortality. A dysfunction in the alternative complement pathway, either acquired or genetic, has been shown to be the main underlying cause. In the last decades, breathtaking advances have been made in understanding the pathophysiology of this rare disease, which has led to more efficient treatment. Recent studies have implicated genes in pathways beyond the alternative complement system, such as DGKE, TSEN2, and INF2 highlighting the importance of personalized management. Eculizumab has brought about dramatic improvements in the treatment of aHUS. Beyond eculizumab, there are many alternative therapeutics in the pipeline that target the complement system. Because of the rarity of aHUS, data from multiple patient registries are very important. The present report aimed to summarize the most important aspects of diagnosing and treating aHUS based on the Turkish national registry and the literature so as to improve clinical practice.

[Genetic analysis of a child with atypical Hemolytic uremic syndrome and nephrotic-range proteinuria]

OBJECTIVE

To explore the clinical characteristics and genetic etiology for a child with atypical Hemolytic uremic syndrome (aHUS) in conjunct with nephrotic level proteinuria.

METHODS

A child patient who had visited the Affiliated Hospital of Qingdao University on June 25, 2020 was selected as the study subject. Clinical data of the patient was collected. Whole exome sequencing (WES) was carried out for the child, and candidate variant was verified by Sanger sequencing of the child and his parents.

RESULTS

The child, an 8-month-old male, had presented mainly with edema, oliguria, hematuria, nephrotic level proteinuria, anemia, thrombocytopenia, increased creatinine and urea, hypercholesterolemia but normal complement levels. Genetic testing revealed that he has harbored compound heterozygous variants of the DGKE gene, namely c.12_18dupGAGGCGG (p.P7fs*37) and c.1042G>T (p.D348Y), which were respectively inherited from his father and mother. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variants were classified as likely pathogenic and variant of uncertain significance, respectively. By combining his clinical manifestations and results of genetic testing, the child was diagnosed with aHUS with nephrotic level proteinuria.

CONCLUSION

For infants and young children with aHUS in conjunct with nephrotic level proteinuria, variants of the DGKE gene should be screened. Above finding has expanded the mutational spectrum of the DGKE gene.

Clinical features of women with thrombotic microangiopathy in pregnancy: A case series from a single Japanese tertiary perinatal care center

AIM

Although perinatal thrombotic microangiopathy has become increasingly understood, the racial characteristics of patients with this condition remain unclear. Herein, we report the characteristics of patients with perinatal thrombotic microangiopathy at a single institution in Japan.

METHODS

We conducted a retrospective study over a 5-year period from January 1, 2017, to December 31, 2021, using the electronic medical records of pregnant women who delivered at the perinatal center of our hospital. We extracted the data of those who developed perinatal thrombotic microangiopathy and evaluated their characteristics at the time of disease onset, final diagnosis, and maternal and fetal outcomes.

RESULTS

Of the 10 224 deliveries that occurred during the 5-year period, only seven patients (0.06%) had perinatal thrombotic microangiopathy. The median pre-pregnant body mass index was 18.65 kg/m2 (minimum 17.3 kg/m2 , maximum 20.7 kg/m2 ). More than half of the patients were conceived by in-vitro fertilization, and 42% these had twin deliveries. Four patients had a history of rheumatic disease. The other three patients without underlying diseases developed thrombotic microangiopathy with HELLP syndrome, and one patient transitioned to atypical hemolytic uremic syndrome.

CONCLUSIONS

Based on low body mass index and in-vitro fertilization, which are characteristic of Japanese women, medical complications and twin pregnancies may be a risk for thrombotic microangiopathy. Additionally, depending on the cause of thrombotic microangiopathy, its timing and onset differed.

Atypical haemolytic uraemic syndrome in a postpartum patient

A postpartum patient presented 1 week following uncomplicated pregnancy and elective repeat caesarean section with acute hypertension, severe anaemia and acute kidney injury. Her workup demonstrated microangiopathic anaemia, thrombocytopenia and liver enzyme elevations. Differential diagnoses included postpartum haemolysis-elevated liver enzyme-low platelet (HELLP) syndrome, haemolytic uraemic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP). She was treated initially with systemic corticosteroids, haemodialysis and plasmapheresis for presumed TTP while awaiting the results of ADAMSTS13 assay performed at an outside laboratory. When reported back as normal, the diagnosis of atypical HUS was established. Eculizumab was administered with rapid improvement of her condition.

Atypical HUS with multiple complement system mutations triggered by synthetic psychoactive drug abuse: a case report

Atypical hemolytic uremic syndrome is a rare disorder with an estimated annual incidence of about two cases per million in the adult population. It is caused by the overactivation of the alternative pathway of the complement system. The disease can be triggered by many factors, including pregnancy, viral diseases, and sepsis; approximately 30% of atypical hemolytic uremic syndrome cases are caused by unknown processes. We present a case of a patient with C3-complement system mutations and aHUS triggered by the use of a new synthetic psychoactive drug.

Genetic investigation of Nordic patients with complement-mediated kidney diseases

Background

Complement activation in atypical hemolytic uremic syndrome (aHUS), C3 glomerulonephropathy (C3G) and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) may be associated with rare genetic variants. Here we describe gene variants in the Swedish and Norwegian populations.

Methods

Patients with these diagnoses (N=141) were referred for genetic screening. Sanger or next-generation sequencing were performed to identify genetic variants in 16 genes associated with these conditions. Nonsynonymous genetic variants are described when they have a minor allele frequency of <1% or were previously reported as being disease-associated.

Results

In patients with aHUS (n=94, one also had IC-MPGN) 68 different genetic variants or deletions were identified in 60 patients, of which 18 were novel. Thirty-two patients had more than one genetic variant. In patients with C3G (n=40) 29 genetic variants, deletions or duplications were identified in 15 patients, of which 9 were novel. Eight patients had more than one variant. In patients with IC-MPGN (n=7) five genetic variants were identified in five patients. Factor H variants were the most frequent in aHUS and C3 variants in C3G. Seventeen variants occurred in more than one condition.

Conclusion

Genetic screening of patients with aHUS, C3G and IC-MPGN is of paramount importance for diagnostics and treatment. In this study, we describe genetic assessment of Nordic patients in which 26 novel variants were found.

Concurrent Cobalamin C and Plasminogen Deficiencies in a Patient with Chronic Thrombotic Microangiopathy

BACKGROUND

Although most patients with atypical hemolytic uremic syndrome (aHUS) have variants in genes participating in alternative complement pathways, rare variants in non-complement pathway-related genes, including DGKE, INF2, MMACHC, PLG, and THBD, have also been described.

CASE PRESENTATION

We report an 18-year-old male patient with renal biopsy-proven chronic thrombotic microangiopathy that raised suspicion of aHUS. Whole-exome sequencing revealed a novel pathogenic homozygous MMACHC c.484G>T (p.Gly162Trp) variant. Subsequently, clinical and laboratory findings confirmed cobalamin C (Cbl C) deficiency. Also, homozygous missense c.1112C>T PLG (p.Thr371Ile) variant was detected (it had been reported as a variant of unknown significance). However, the low serum plasminogen (PLG) activity proved the pathogenicity of c.1112C>T. Hence, the patient was diagnosed with concurrent Cbl C and PLG deficiencies. Segregation analysis revealed that the mother and father had the same heterozygous PLG and MMACHC variants. PLG variants have generally been described in aHUS patients concomitant with complement gene variants in the literature; therefore, the association between aHUS and PLG variants is controversial. The possible contribution of PLG deficiency to thrombotic microangiopathy was also discussed in this case.

CONCLUSION

Non-complement-mediated aHUS is an exceptional disorder. A limited number of genes are involved in this entity. To our knowledge, this is the first aHUS patient diagnosed with both Cbl C and PLG deficiencies in the literature.

[Comparative characteristics of the complement system in patients with C3-glomerulopathy and atypical hemolytic uremic syndrome of chronic course who suffered an acute episode of thrombotic microangiopathy]

AIM

To compare changes in the complement system in C3-glomerulopathy (C3-GP) and atypical hemolytic uremic syndrome (aHUS) after the relief of an acute episode of thrombotic microangiopathy.

MATERIALS AND METHODS

The study included 8 patients diagnosed with C3-GP and 8 with aHUS in remission. The blood levels of the complement system components were determined: C3, C4, C3a, C5a, factor H (CFH), factor B (CFB), membrane-attacking complex (MAC), antibodies to C3b (anti-C3b-AT), the level of hemolytic activity (CH50), the content of factor D (CFD) in the urine.

RESULTS

C3 and CH50 levels were within the reference range in both groups, however, in the C3-GP group they were at the lower limit, and C3 level was significantly lower than in the aHUS group: 0.56 [0.44; 0.96] vs 1.37 [1.16; 2.52] (p=0.003). CFB increased level was detected in both groups, but in the C3-GP group it was significantly lower than in the aHUS group - 275.1 [222.1; 356.6] vs 438.7 [323.3; 449.3] (p=0.010). C3a, C5a and MAC levels were increased in both groups, but the maximum was in the C3-GP group, and the MAC level in the C3-GP group was 2 times higher than that in aHUS, and these differences reached statistical significance - 123 555±6686 vs 5603±1294 (p=0.036). CFH and CFD levels was increased in both groups, but their highest values was in the aHUS group.

CONCLUSION

Alternative complement pathway activation signs were present in both groups of patients with complement-mediated nephropathies, regardless the stage of the disease. In C3-GP, alternative complement pathway activation was more pronounced than in aHUS after the relief of an acute episode of thrombotic microangiopathy.

[Various phenotypes of postpartum atypical hemolytic uremic syndrome: the role of genetic testing in determining prognosis. Case report]

We report a case of atypical hemolytic uremic syndrome (aHUS) that occurred after childbirth in a patient with a history of numerous recurrent episodes of TMA with nephrotic proteinuria and impaired renal function. At 33 weeks of the first spontaneous pregnancy, proteinuria up to 0.8 g/l was first registered, at 38 weeks she was hospitalized with proteinuria, reaching a maximum of 13 g/l, she was delivered promptly, after which progressive thrombocytopenia was noted over the next few days (up to 44×109/l) and anemia and severe arterial hypertension, which could not be corrected by several groups of antihypertensive drugs. Initiated plasma therapy had no effect. After exclusion of all other causes of TMA, therapy with eculizumab was initiated, which made it possible to quickly and completely stop the phenomena of TMA. The presented observation demonstrates the successful treatment of recurrent course of aHUS with eculizumab with the achievement of complete recovery of kidney function in a patient with a homozygous mutation in the MCP gene. It is worth noting the importance of genetic research even in those situations where clinically aHUS is beyond doubt.

Ischemic cerebrovascular complications with initial presentation of genetic atypical hemolytic uremic syndrome

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare disease, with scarce reports of neurologic manifestations in the acute setting. Ischemic cortical infarcts concurrently with aHUS presentation have not been described in adult patients.

CASE DESCRIPTION

A 46-year-old male presented with acutely declining mental status and progressive weakness, in the setting of longstanding hypertension and known type B aortic dissection. Urgent neuroimaging showed bilateral multifocal multiterritorial ischemic infarcts, concerning for an embolic source or hypercoagulable state. Systemic workup was notable for microangiopathic hemolytic anemia and acute kidney injury. Empiric plasmapheresis was initiated for presumed thrombotic thrombocytopenic purpura. Broad workup did not support such a diagnosis, and kidney biopsy showed findings compatible with aHUS. Additional blood testing showed increased complement pathway activity. Shiga toxin was negative, and overall clinical picture fit with aHUS as diagnosis. Treatment with complement inhibitor was started and patient gradually recovered. Genetic testing confirmed a pertinent pathogenic mutation, CFHR1 homozygous deletion.

CONCLUSION

Acute multifocal multiterritorial ischemic infarcts and systemic thrombotic microangiopathy may be a manifestation of aHUS, and with associated genetic mutation, even in adult population.

Genotypic analysis of a large cohort of patients with suspected atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. Complement and coagulation gene variants have been associated with aHUS susceptibility. We assessed the diagnostic yield of a next-generation sequencing (NGS) panel in a large cohort of Canadian patients with suspected aHUS. Molecular testing was performed on peripheral blood DNA samples from 167 patients, collected between May 2019 and December 2021, using a clinically validated NGS pipeline. Coding exons with 20 base pairs of flanking intronic regions for 21 aHUS-associated or candidate genes were enriched using a custom hybridization protocol. All sequence and copy number variants were assessed and classified following American College of Medical Genetics guidelines. Molecular diagnostic results were reported for four variants in three individuals (1.8%). Twenty-seven variants of unknown significance were identified in 25 (15%) patients, and 34 unique variants in candidate genes were identified in 28 individuals. An illustrative patient case describing two genetic alterations in complement genes is presented, highlighting that variable expressivity and incomplete penetrance must be considered when interpreting genetic data in patients with complement-mediated disease, alongside the potential additive effects of genetic variants on aHUS pathophysiology. In this cohort of patients with suspected aHUS, using clinical pipelines for genetic testing and variant classification, pathogenic/likely pathogenic variants occurred in a very small percentage of patients. Our results highlight the ongoing challenges in variant classification following NGS panel testing in patients with suspected aHUS, alongside the need for clear testing guidance in the clinical setting. KEY MESSAGES: • Clinical molecular testing for disease associated genes in aHUS is challenging. • Challenges include patient selection criteria, test validation, and interpretation. • Most variants were of uncertain significance (31.7% of patients; VUS + candidates). • Their clinical significance may be elucidated as more evidence becomes available.  • Low molecular diagnostic rate (1.8%), perhaps due to strict classification criteria. • Case study identified two likely pathogenic variants; one each in MCP/CD46 and CFI.

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.

Hemolytic Uremic Syndrome: A Case Report

Thrombotic microangiopathy is a pathological condition comprised of microvascular thrombosis involving any body organ leading to thrombocytopenia, coombs-negative hemolytic anemia, and end-organ damage. The clinical presentation of the case shows typical hemolytic uremic syndrome, however, lab reports show atypical hemolytic uremic syndrome (low C3). Pain abdomen and loose stool with some signs of dehydration were initial presentations. Early initiation of renal replacement therapy and management of dehydration was done. Simple diarrhea can also manifest as acute kidney injury with the hemolytic uremic syndrome. Hence we should keep hemolytic uremic syndrome as the differential diagnosis of diarrhea. Irrespective of lab parameters, early management in line with the typical hemolytic uremic syndrome should be done for better outcomes.

Keywords

anemia; case reports; dehydration; renal replacement therapy.

Atypical hemolytic uremic syndrome: Consensus of diagnosis and treatment in Taiwan

Atypical hemolytic uremic syndrome (aHUS), characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, is a rare but life-threatening systemic disorder caused by the dysregulation of the complement pathway. Current advances in molecular analysis and pathogenesis have facilitated the establishment of diagnosis and development of effective complement blockade. Based on this recent consensus, we provide suggestions regarding the diagnosis and management of aHUS in Taiwan. The diagnosis of aHUS is made by the presence of TMA with normal ADAMTS13 activity without known secondary causes. Although only 60% of patients with aHUS have mutations in genes involving the compliment and coagulation systems, molecular analysis is suggestive for helping establish diagnosis, clarifying the underlying pathophysiology, guiding the treatment decision-making, predicting the prognosis, and deciding renal transplantation. Complement blockade, anti-C5 monoclonal antibody, is the first-line therapy for patients with aHUS. Plasma therapy should be considered for removing autoantibody in patients with atypical HUS caused by anti-CFH or complement inhibitor is unavailable.

Clinical characteristics and outcomes of a patient population with atypical hemolytic uremic syndrome and malignant hypertension: analysis from the Global aHUS registry

INTRODUCTION

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) often caused by alternative complement dysregulation. Patients with aHUS can present with malignant hypertension (MHT), which may also cause TMA.

METHODS

This analysis of the Global aHUS Registry (NCT01522183) assessed demographics and clinical characteristics in eculizumab-treated and not-treated patients with aHUS, with (n = 71) and without (n = 1026) malignant hypertension, to further elucidate the potential relationship between aHUS and malignant hypertension.

RESULTS

While demographics were similar, patients with aHUS + malignant hypertension had an increased need for renal replacement therapy, including kidney transplantation (47% vs 32%), and more pathogenic variants/anti-complement factor H antibodies (56% vs 37%) than those without malignant hypertension. Not-treated patients with malignant hypertension had the highest incidence of variants/antibodies (65%) and a greater need for kidney transplantation than treated patients with malignant hypertension (65% vs none). In a multivariate analysis, the risk of end-stage kidney disease or death was similar between not-treated patients irrespective of malignant hypertension and was significantly reduced in treated vs not-treated patients with aHUS + malignant hypertension (adjusted HR (95% CI), 0.11 [0.01-0.87], P = 0.036).

CONCLUSIONS

These results confirm the high severity and poor prognosis of untreated aHUS and suggest that eculizumab is effective in patients with aHUS ± malignant hypertension. Furthermore, these data highlight the importance of accurate, timely diagnosis and treatment in these populations and support consideration of aHUS in patients with malignant hypertension and TMA.

TRIAL REGISTRATION DETAILS

Atypical Hemolytic-Uremic Syndrome (aHUS) Registry. Registry number: NCT01522183 (first listed 31st January, 2012; start date 30th April, 2012).

How I diagnose and treat atypical hemolytic uremic syndrome

Our understanding and management of atypical hemolytic uremic syndrome (aHUS) have dramatically improved in the last decade. aHUS has been established as a prototypic disease resulting from a dysregulation of the complement alternative C3 convertase. Subsequently, prospective nonrandomized studies and retrospective series have shown the efficacy of C5 blockade in the treatment of this devastating disease. C5 blockade has become the cornerstone of the treatment of aHUS. This therapeutic breakthrough has been dulled by persistent difficulties in the positive diagnosis of aHUS, and the latter remains, to date, a diagnosis by exclusion. Furthermore, the precise spectrum of complement-mediated renal thrombotic microangiopathy is still a matter of debate. Nevertheless, long-term management of aHUS is increasingly individualized and lifelong C5 blockade is no longer a paradigm that applies to all patients with this disease. The potential benefit of complement blockade in other forms of HUS, notably secondary HUS, remains uncertain.

Atypical Hemolytic Uremic Syndrome Occurring After Receipt of mRNA-1273 COVID-19 Vaccine Booster: A Case Report

Atypical hemolytic uremic syndrome (aHUS) is a subtype of thrombotic microangiopathy (TMA) characterized by a dysregulation of the alternative complement pathway. Here, we report a previously healthy 38-year-old woman in whom aHUS developed after a COVID-19 vaccine booster. One day after receipt of a booster dose of mRNA-1273 vaccine, she felt ill. Because of persistent headache, nausea, and general malaise, she went to her general practitioner, who referred her to the hospital after detecting hypertension and acute kidney injury. A diagnosis of TMA was made. Her treatment consisted of blood pressure control, hemodialysis, plasma exchange, and respiratory support. Kidney biopsy confirmed the diagnosis of acute TMA. The patient was referred for treatment with eculizumab, and kidney function improved after initiation of this therapy. Genetic analysis revealed a pathogenic C3 variant. SARS-CoV-2 infection as a trigger for complement activation and development of aHUS has been described previously. In addition, there is one reported case of aHUS occurring after receipt of the adenovirus-based COVID-19 vaccine ChAdOx1 nCoV-19, but, to our knowledge, this is the first case of aHUS occurring after a booster dose of an mRNA COVID-19 vaccine in a patient with an underlying pathogenic variant in complement C3. Given the time frame, we hypothesize that the vaccine probably was the trigger for development of aHUS in this patient.

The treatment of atypical hemolytic uremic syndrome with eculizumab in pediatric patients: a systematic review

BACKGROUND

The atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy associated with high morbidity and high mortality. Eculizumab, a humanized anti-C5 monoclonal antibody, was the first medication approved for treating aHUS in 2011.

OBJECTIVE

The objective of this study is to evaluate the efficacy and safety of eculizumab treatment in pediatric patients with aHUS.

DATA SOURCES

We consulted PubMed, Scopus, SciELO, and Cochrane Library databases in July 2021. The descriptors were as follows: "Atypical Hemolytic Uremic Syndrome," "aHUS," "eculizumab," "Pediatrics," "Pediatric," "Child," "Children," "Adolescent."

STUDY ELIGIBILITY CRITERIA

The study eligibility criteria are as follows: clinical trials and observational studies that included pediatric patients with aHUS diagnosis and who were treated with eculizumab.

PARTICIPANTS AND INTERVENTIONS

The participants are pediatric patients, up to 18 years old, with aHUS. The intervention was eculizumab treatment.

STUDY APPRAISAL

For quality assessment, we used the Newcastle-Ottawa Scale, the National Institutes of Health (NIH) quality assessment tool for case series studies, and the Risk of Bias In Non-Randomized Studies of Interventions (ROBINS-I) tool.

RESULTS

The initial search retrieved 433 studies, from which 15 were selected after complete assessment: 9 cohorts, 4 case series, and 1 clinical trial. The publication date ranged from 2015 to 2021. In total, 940 pediatric patients were included, and 682 received eculizumab. All studies reported improvements in renal and hematological parameters in most of the patients treated with eculizumab. The mortality rate was 1.6% for all patients treated with eculizumab.

LIMITATIONS

The number of studies is limited, and the included studies were methodologically heterogeneous. The studies were mostly observational and many had small sample sizes.

CONCLUSIONS

Eculizumab appears to be safe and effective for the treatment of aHUS in pediatric patients. More research is necessary to establish long-term efficacy, safety, and time of discontinuation.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42021266255.

Maternal morbidity and mortality in pregnant/postpartum women with suspected HELLP syndrome identifiable as probable thrombotic thrombocytopenic purpura or atypical hemolytic uremic syndrome by high LDH to AST ratio

OBJECTIVE

To describe findings in 8 women initially diagnosed as presumptive HELLP Syndrome, eventually confirmed as TTP/aHUS as distinguished by elevated calculated LDH:AST ratio > 22:1.

METHODS

All medicolegal files of patients evaluated between 1986 and 2015 with presumptive HELLP syndrome but later determined to have TTP/aHUS had LDH:AST ratios evaluated throughout care.

RESULTS

Fifty-eight pregnant/postpartum women presented with a diagnosis of presumptive HELLP syndrome. In the final analysis, 8 women had TTP/aHUS characterized by severe thrombocytopenia (<20 000/μl) at admission, rare epigastric pain, and the consistent demonstration of a very high calculated total LDH to AST ratio. This calculation greatly exceeded 22:1 with TTP/aHUS (mean = 32:1) versus 2:1 with HELLP and could be consistently demonstrated throughout care. Six of 8 women with TTP/aHUS died.

CONCLUSION

Correctly distinguishing between HELLP syndrome versus an imitator disorder continues to challenge obstetric specialists. This medicolegal data supplements prior findings supporting the concept of the LDH:AST ratio as a useful screening tool for clinicians to differentiate TTP/aHUS apart from HELLP syndrome in order to facilitate earlier hematology consultation, patient referral to tertiary care and emergent hemotherapy for these mothers.

Atypical hemolytic uremic syndrome triggered by mRNA vaccination against SARS-CoV-2: Case report

Atypical hemolytic uremic syndrome (aHUS), also called complement-mediated hemolytic uremic syndrome (CM-HUS), is a rare disease caused by dysregulation in the alternative complement activation pathway. It is a life-threatening condition causing ischemia of a number of organs, and it typically causes acute kidney injury. This disorder may be triggered by various factors including viral or bacterial infections, pregnancy, surgery, and injuries. In about 60% of cases, the genetic origin of the disease can be identified—commonly mutations affecting complementary factor H and MCP protein. Eculizumab, a monoclonal antibody to the C5 component of the complement, represents the current effective treatment.We describe a case of a young woman with a previous history of polyvalent allergies, who developed atypical hemolytic uremic syndrome after vaccination with mRNA vaccine against SARS-CoV-2. The disease manifested by scleral bleeding, acute renal insufficiency, anemia, and thrombocytopenia. The patient was treated with plasma exchanges without sufficient effect; remission occurred only after starting treatment with eculizumab. Genetic examination showed that the patient is a carrier of multiple inherited risk factors (a rare pathogenic variant in CFH, MCPggaac haplotype of the CD46 gene, and the risk haplotype CFH H3). The patient is currently in hematological remission with persistent mild renal insufficiency, continuing treatment with eculizumab/ravulizumab. By this case report, we meant to point out the need for careful monitoring of people after vaccination, as it may trigger immune-mediated diseases, especially in those with predisposing factors.

The roles of homocysteinemia and methylmalonic acidemia in kidney injury in atypical hemolytic uremic syndrome caused by cobalamin C deficiency

BACKGROUND

Cobalamin C (cblC), a vitamin B12 processing protein, plays a crucial role in metabolism for the conversion of homocysteine to methionine and methylmalonyl-CoA to succinyl-CoA. CblC deficiency, an inborn error of cobalamin processing, is a rare cause of atypical hemolytic-uremic syndrome (aHUS) and results in hyperhomocysteinemia and methylmalonic aciduria. Both substances are thought to contribute to thrombotic microangiopathy (TMA) in cblC deficiency patients. However, the roles of homocysteine and methylmalonic acid (MMA) in these patients remain unclear. We want to shed more light on the contributions of homocysteine and MMA levels as contributing factors for thrombotic microangiopathy (TMA)/aHUS by a follow-up of a cblC deficiency patient over 6 years.

CASE DIAGNOSIS

A 27-day-old Hispanic female presented with abnormal C3-carnitine on her newborn screen, poor feeding, decreased activity, and oligouria. She was diagnosed with cblC deficiency after laboratory results revealed elevated serum homocysteine, and serum MMA along with genetic testing showing a homozygous pathogenic frameshift variant in MMACHC. The patient developed aHUS and acute kidney injury (AKI), which resolved after appropriate therapy. Over 6 years, she continued to have normal kidney function with no thrombocytopenia despite persistently elevated homocysteine and MMA levels.

CONCLUSION

We question the roles of homocysteine and MMA as causative of aHUS/TMA in cblC deficiency as they remained elevated during follow-up but did not result in aHUS/TMA or AKI. Hyperhomocysteinemia and/or MMA caused by other metabolic diseases do not result in aHUS/TMA or AKI. This suggests that other nephrotoxic factors may trigger aHUS/TMA in cblC patients.

Management of atypical uremic hemolytic syndrome in pregnant patient

Atypical uremic haemolytic syndrome is a variant of thrombotic micro-andiopathy characterized by non-autoimmune hemolytic anemia, thrombocytopenia and acute renal failure as a result of excessive activation of the complement. Up to 60% of patients have mutations in the genes that encode the complement system. A disensing factor is required for its manifestation, including gestation. It is an entity with a high morbidity, which can decrease drastically if an early diagnosis is made and appropriate treatment is initiated. Administration of ecuilizumab has demonstrated rapid process disruption, reducing the need for extrarenal purification therapies and improving renal function and patient prognosis.

Atypical Hemolytic Uremic Syndrome-Associated FHR1 Isoform FHR1*B Enhances Complement Activation and Inflammation

Atypical hemolytic uremic syndrome (aHUS) is a rare but severe type of thrombotic microangiopathy that is triggered by the abnormal activation of the alternative complement pathway. Previous studies have reported that three completely linked coding variants of CFHR1 form two haplotypes, namely, CFHR1*A (c.469C, c.475C, c.523G) and CFHR1*B (c.469T, c.475G, c.523C). CFHR1*B is associated with susceptibility to aHUS. To explore the genetic mechanism by which CFHR1 isoforms contribute to aHUS, we compared the structures of FHR1*A and FHR1*B by homology modeling and found differences in the angles between SCR3 and SCR4-SCR5, as FHR1*B had a larger angle than FHR1*A. Then, we expressed FHR1*A and FHR1*B recombinant proteins and compared their functions in complement system regulation and inflammation. We found that FHR1*B presented a significantly higher capacity for binding C3b and necrotic cells than FHR1*A. In a cofactor assay, the FHR-1*B showed stronger influence on FH mediated cofactor function than the FHR-1*A, resulted in fewer C3b cleavage products. In the C3 convertase assays, FHR1*B showed more powerful effect compared with FHR1*A regarding to de-regulate FH function of inhibition the assembling of C3bBb. Additionally, we also found that FHR1*B triggered monocytes to secrete higher levels of IL-1β and IL-6 than FHR1*A. In the present study, we showed that variants of CFHR1 might differently affect complement activation and sterile inflammation. Our findings provide a possible mechanism underlying the predisposition to aHUS caused by CFHR1 isoform CFHR1*B.

[CME: Diagnostic Approach and Management of Thrombotic Microangiopathy]

CME: Diagnostic Approach and Management of Thrombotic Microangiopathy Abstract. Thrombotic microangiopathies (TMA) are characterized by organ thrombosis induced by endothelial injury. They present with thrombocytopenia, hemolytic anemia and schistocytes. In case of an underlying disease-causing TMA, the treatment of the underlying disease is essential. Primary TMAs are divided into thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome and atypical hemolytic-uremic syndrome. Differentiation of these entities is essential, as fast initiation of empiric treatment might be life-saving and disease-modifying treatments for the different entities do exist.

[A hemolytic episode following COVID-19 in a case with atypical hemolytic uremic syndrome]

Atypical hemolytic uremic syndrome (aHUS) is a lethal disease resulting in systemic thrombotic microangiopathies due to complement dysregulation. Immune activation by viral infections, such as SARS-CoV-2, may trigger hemolytic attack. A 38-year-old man, who had been previously diagnosed with aHUS due to complement component 3 mutation, was proven to be positive for SARS-CoV-2 without respiratory symptoms. No specific intervention was given to the patient, and he developed hematuria and oliguria three days after diagnosis. The patient was subsequently referred to our hospital and treated with eculizumab (900 mg). Afterward, the hemolytic symptoms improved rapidly. To the best of our knowledge, there have been reports of at least ten cases of hemolysis triggered by COVID-19 in patients with aHUS, and a potential clinical benefit of eculizumab for hemolytic attack, as well as for COVID-19, has been suggested. Here, we report the findings of a case, which indicate the efficacy of eculizumab introduction at an early stage.

POSTPARTUM RENAL THROMBOTIC MICROANGIOPATHY: A TURN-BASED DIFFERENTIAL DIAGNOSIS

Pregnancy-associated renal thrombotic microangiopathy is a rare condition with poor maternal outcome. Pregnancy may trigger atypical hemolytic uremic syndrome or thrombotic thrombocytopenic purpura. The article describes the clinical case of a 37-year-old woman who developed acute renal failure following complicated delivery. A turn-based differential diagnosis of atypical hemolytic uremic syndrome was performed. Unwarranted discontinuation of the targeted therapy with Eculisumab led to the development of chronic renal failure. Pregnancy-associated atypical hemolytic uremic syndrome is a life-threatening condition rarely seen in pregnancy making its early recognition difficult. As thrombotic microangiopathies require urgent treatment, plasmapheresis should be started as soon as they are suspected, followed by Eculisumab after the confirmation of the diagnosis of atypical hemolytic uremic syndrome. This may contribute to reducing maternal morbidity and mortality rates.

Coexistence of Anti Neutrophilic Cytoplasmic Antibody (ANCA) Negative Renal Limited Vasculitis and Atypical- Hemolytic Uremic Syndrome (aHUS)

Small vessel necrotizing vasculitis is divided into two groups; Immune complex mediated and Pauci immune vasculitis. Hemolytic uremic syndrome (HUS) is a rare disease manifested as microangiopathic hemolytic anemia, thrombocytopenia and renal involvement. The coexistence of ANCA negative vasculitis and atypical HUS (aHUS) is rare. We describe a case of a 40 years old lady with rapidly declining kidney function. Renal Biopsy revealed Crescentic necrotizing glomerulonephritis (CGN). She was treated with plasmapheresis alternating with hemodialysis (HD) and immunosuppressive therapy. One month later she developed hemolytic anemia with peripheral schistocytes and thrombocytopenia and diagnosed as aHUS. Same treatment continued and her aHUS resolved spontaneously over one week. However her kidney functions didn't improve and ended up with end stage renal disease (ESRD). DOI: 10.52547/ijkd.6443.

Atypical Hemolytic Uremic Syndrome (aHUS) and Adenosine Deaminase (ADA)-Deficient Severe Combined Immunodeficiency (SCID)-Two Diseases That Exacerbate Each Other: Case Report

Hemolytic uremic syndrome (HUS) is defined by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury (AKI). Atypical HUS (aHUS), distinguished by its etiology, is caused by uncontrolled overactivation of the alternative complement pathway. The correct diagnosis of aHUS is complex and involves various gene mutations. Severe combined immunodeficiency (SCID), characterized by severe T-cell lymphocytopenia and a lack of antigen-specific T-cell and B-cell immune responses, is of seldom occurrence. In 10–15% of pediatric patients, SCID is caused by adenosine deaminase (ADA) deficiency. The authors describe the case of a boy who suffered from both aHUS and ADA-deficient SCID. At the age of 9 months, the patient presented acute kidney injury with anuria and coagulopathy. The diagnosis of aHUS was established on the basis of alternative complement pathway deregulation and disease-associated gene mutations. Further examination revealed immune system failure and, at the age of 13 months, the ADA deficiency was confirmed by genetic tests and the boy was diagnosed with ADA-SCID. ADA SCID has recently been described as a possible triggering factor of aHUS development and progression. However, more research is required in this field. Nevertheless, it is crucial in clinical practice to be aware of these two co-existing life-threatening diseases.

An Atypical Case of Thrombotic Microangiopathy Secondary to Acute Pancreatitis

Thrombotic microangiopathies (TMAs) are a group of disorders characterized by microangiopathic hemolytic anemia, thrombocytopenia, and end-organ damage. It can often be challenging to determine the underlying etiology. Our patient presented with acute pancreatitis and later developed thrombocytopenia and hemolytic anemia, along with acute renal failure. A working diagnosis of an atypical hemolytic uremic syndrome was made; however, he improved clinically and eculizumab was not started. Workup for the atypical hemolytic uremic syndrome was unrevealing. The authors propose that the pancreatitis triggered a secondary TMA, which although rare, has previously been described in the literature. This case illustrates the diagnostic and therapeutic challenges associated with TMAs.

Kidney transplant in patients with atypical hemolytic uremic syndrome in the anti-C5 era: single-center experience with tailored Eculizumab

RATIONALE AND OBJECTIVE

Patients with atypical hemolytic uremic syndrome (aHUS) have long been considered ineligible for kidney transplantation (KTx) in several centers due to the high risk of disease recurrence, graft loss and life-threatening complications. The availability of Eculizumab (ECU) has now overcome this problem. However, the best approach towards timing, maintenance schedule, the possibility of discontinuation and patient monitoring has not yet been clearly established.

STUDY DESIGN

This is a single center case series presenting our experience with KTx in aHUS.

SETTING AND PARTICIPANTS

This study included 26 patients (16 females) with a diagnosis of aHUS, who spent a median of 5.5 years on kidney replacement therapy before undergoing KTx. We compared the aHUS relapse rate in three groups of patients who underwent KTx: patients who received no prophylaxis, patients who underwent plasma exchange, those who received Eculizumab prophylaxis. Complement factor H-related disease was by far the most frequent etiology (n = 19 patients).

RESULTS

Untreated patients and patients undergoing pre-KTx plasma exchange prophylaxis had a relapse rate of 0.81 (CI 0.30-1.76) and 3.1 (CI 0.64-9.16) events per 10 years cumulative observation, respectively, as opposed to 0 events among patients receiving Eculizumab prophylaxis. The time between Eculizumab doses was tailored based on classic complement pathway activity (target to < 30%). Using this strategy, 12 patients are currently receiving  Eculizumab every 28 days, 5 every 24-25 days, and 3 every 21 days.

CONCLUSION

Our experience supports the prophylactic use of Eculizumab in patients with a previous history of aHUS undergoing KTx, especially when complement dysregulation is well documented by molecular biology.

Complement C3 Deposition on Endothelial Cells Revealed by Flow Cytometry

The three pathways of the complement system converge toward the cleavage of the central complement component C3 into its activated fragments, with C3b being able to bind covalently to the activating surface. The endothelial cells are among the major targets for complement attack in pathological conditions, as the atypical hemolytic uremic syndrome. Therefore, study of complement C3 deposition on endothelial cells by flow cytometry is a sensitive test to measure complement activation. This test can be used as a research or clinical tool to test complement activation induced by patients' sera or to test the functional consequences of newly discovered complement mutations as well as different triggers of endothelial cells injury.

Hemolytic Tests Exploring Factor H Functional Activities

Impairment of the complement regulatory protein Factor H (FH) is implicated in the physiopathological mechanisms of different diseases like atypical hemolytic and uremic syndrome and C3 glomerulopathies. It may be due to genetic abnormalities or acquired with the development of autoantibodies. FH has several ligands; therefore, the exploration of its functions requires to perform different tests. Among them, two hemolytic tests are very useful because they give specific and complementary information about FH functions. The first one is dedicated to explore the FH capacity to dissociate the alternative pathway C3 convertase, whereas the second one is designed to explore the capacity of FH to bind cell surfaces and to protect them from complement attack. This chapter describes the procedures to perform these two hemolytic tests, exploring in a complementary way the FH functionality.

Functional Hemolytic Test for Complement Alternative Pathway Convertase Activity

The complement system is a key part of innate immunity. However, if the system becomes dysregulated, damage to healthy host cells can occur, especially to the glomerular cells of the kidney. The convertases of the alternative pathway of the complement system play a crucial role in complement activation. In healthy conditions, their activity is strictly regulated. In patients with diseases caused by complement alternative pathway dysregulation, such as C3 glomerulopathy and atypical hemolytic uremic syndrome, factors can be present in the blood that disturb this delicate balance, leading to convertase overactivity. Such factors include C3 nephritic factors, which are autoantibodies against the C3 convertase that prolong its activity, or genetic variants resulting in a stabilized convertase complex. This chapter describes a method in which the activity and stability of the alternative pathway convertases can be measured to detect aberrant serum factors causing convertase overactivity.

Diagnostic dilemma in postpartum associated hemolytic uremic syndrome in a 38th week pregnant 31-year-old Congolese: a case report

BACKGROUND

Thrombotic microangiopathy is associated with HELLP syndrome, thrombotic thrombocytopenic purpura, or atypical hemolytic uremic syndrome (aHUS) during pregnancy. Standard laboratory and physical examinations can help distinguish between these three diseases promptly and guide their management. This is critical because their managements and prognoses differ considerably. The ADAMTS13 test, complement tests, and biopsies can help ascertain the diagnosis; however, they take time, and are not widely available. In this case report, we present a case that highlights the diagnostic and therapeutic dilemmas associated with the aforementioned diseases.

CASE PRESENTATION

A 31-year old P3G3 patient presented at 38 weeks with high blood pressure, bilateral pitting edema, and a low fetal heart rate. A cesarean section was performed to extract the fetus. On postoperative day 2, the suites were marked by anemia, low platelet count, acute kidney injury, declining liver function, and the presence of schistocytes on the peripheral thin smear. The patient was lucid, coherent, and presented no neurological deficits. The ADAMTS13 test and anti-complement therapy were not readily available, so the team made a presumptive diagnosis of aHUS based on the history, clinical presentation, and standard laboratory results. Due to a lack of anticomplement therapy, the patient was prescribed four sessions of hemodialysis. The renal function and platelet count gradually increased, and the patient was discharged on postoperative day 18. The patient was followed for over a year and did not present relapses of thrombocytopenia or microangiopathic hemolytic anemia.

CONCLUSIONS

The prompt diagnosis and management of aHUS lead to favorable outcomes. Healthcare providers should be able to rapidly differentiate between pregnancy-associated thrombotic microangiopathies and prescribe appropriate management. Here, we highlighted the challenges of diagnosing and managing postpartum associated aHUS in a low-resource setting.

Economic Impact of Early-in-Hospital Diagnosis and Initiation of Eculizumab in Atypical Haemolytic Uraemic Syndrome

BACKGROUND

Atypical haemolytic uraemic syndrome (aHUS) is a rare, potentially life-threatening condition caused by dysregulation of the complement pathway. Eculizumab is currently the only approved treatment for this disorder.

OBJECTIVE

Our objective was to investigate the impact of early administration of eculizumab on inpatient resource use and hospitalisation costs in 222 patients with aHUS.

METHODS

We conducted a retrospective analysis of the Premier Perspective® Hospital Database, including patients with a diagnosis of aHUS and evidence of eculizumab use for aHUS. Early initiation was defined as having received eculizumab within 7 days of admission, with late initiation defined as starting eculizumab on day 8 or later. This date represents the average time required to obtain a specific diagnostic test to discriminate aHUS from a similar haemolytic syndrome that requires a different treatment. Outcome measures were time from first eculizumab initiation to discharge, discharge status or death, days spent in the intensive care unit (ICU), readmission indicators, dialysis indicators, and total hospital costs. Time from first eculizumab initiation to discharge was analysed using a generalised linear model with a log link and an assumed underlying negative binomial distribution. Logistic regression models were used to test the statistical significance of early versus late initiation as a predictor of the occurrence of readmissions, dialysis, and death. Total hospital costs were analysed using a generalised linear model with a log link and an assumed underlying gamma distribution.

RESULTS

Before modelling, total length of stay and ICU duration were significantly longer for late initiators than for early initiators, and significantly more late initiators were readmitted within 90 days. Late initiation was associated with significantly higher hospital costs than early initiation. After multivariable analysis, late initiators were 3.2 times more likely to require dialysis. However, there was no significant association between early initiation and time to discharge, readmission, or death for any definition or early initiation after multivariable analysis. Estimated total hospital costs (year 2017 values) were $US103,557 in late initiators and $US85,776 in early initiators (p = 0.0024).

CONCLUSION

Initiation of eculizumab within 7 days of hospitalisation is associated with lower dialysis rates, less time in ICU, less plasmapheresis, and lower hospitalisation costs compared with late initiation.

Consensus regarding diagnosis and management of atypical hemolytic uremic syndrome

Thrombotic microangiopathy (TMA) is defined by specific clinical characteristics, including microangiopathic hemolytic anemia, thrombocytopenia, and pathologic evidence of endothelial cell damage, as well as the resulting ischemic end-organ injuries. A variety of clinical scenarios have features of TMA, including infection, pregnancy, malignancy, autoimmune disease, and medications. These overlapping manifestations hamper differential diagnosis of the underlying pathogenesis, despite recent advances in understanding the mechanisms of several types of TMA syndrome. Atypical hemolytic uremic syndrome (aHUS) is caused by a genetic or acquired defect in regulation of the alternative complement pathway. It is important to consider the possibility of aHUS in all patients who exhibit TMA with triggering conditions because of the incomplete genetic penetrance of aHUS. Therapeutic strategies for aHUS are based on functional restoration of the complement system. Eculizumab, a monoclonal antibody against the terminal complement component 5 inhibitor, yields good outcomes that include prevention of organ damage and premature death. However, there remain unresolved challenges in terms of treatment duration, cost, and infectious complications. A consensus regarding diagnosis and management of TMA syndrome would enhance understanding of the disease and enable treatment decision-making.

A case of Moyamoya disease complicated by aHUS in a patient with a history of marginal zone B-cell lymphoma: lightning strikes thrice?

Atypical haemolytic uraemic syndrome (aHUS) is a rare, acquired thrombotic microangiopathy, mediated by complement activation, in very sick patients. Moyamoya is similarly a rare disease in which stenosis or occlusion of segment(s) of the anterior cerebral circulation leads to the formation of many thin collaterals. Other reports have described an association between HUS and Moyamoya disease in the paediatric population. However, this case study presents the exceptionally rare presentation of an adult with aHUS and Moyamoya disease in a patient who was treated with rituximab for marginal zone B-cell lymphoma.

Pregnancy Prolongation After Eculizumab Use in Early-Onset Preeclampsia

BACKGROUND

Untreated microangiopathic hemolytic anemia in pregnancy is associated with adverse maternal and perinatal outcomes. Accurate diagnosis is challenging owing to nonspecific clinical features and pathologic findings. Timely initiation of appropriate management is essential to optimize maternal and perinatal outcomes.

CASE

A 26-year-old primiparous woman presented at 20 weeks of gestation with new-onset microangiopathic hemolytic anemia on a background of poorly controlled type 1 diabetes. She received eculizumab for presumed atypical hemolytic uremic syndrome. At 24 weeks of gestation, she developed superimposed early-onset preeclampsia; she delivered at 27 weeks of gestation after continuing eculizumab.

CONCLUSION

Eculizumab may prolong pregnancy in early-onset preeclampsia. Additional research is needed to assess short-term and long-term maternal and newborn outcomes.

[Diagnostic and Therapeutic Challenges in Atypical Hemolytic Uremic Syndrome: A Case Report]

The atypical hemolytic uremic syndrome comprises a thrombotic microangiopathy resulting from the complement alternate pathway hyperactivation. Its severity requires early diagnosis and treatment. The differential diagnosis includes typical hemolytic uremic syndrome (associated with Shiga toxin) and thrombotic thrombocytopenic purpura (associated with deficient activity of ADAMTS13). The only specific treatment currently available for atypical hemolytic uremic syndrome is eculizumab. We describe the case of a child with atypical hemolytic uremic syndrome diagnosed in the context of bloody diarrhea, complicated by neurological involvement that posed several diagnostic and therapeutic challenges.

Outcomes in patients with atypical hemolytic uremic syndrome treated with eculizumab in a long-term observational study

BACKGROUND

There are limited long-term outcome data in eculizumab-treated patients with atypical hemolytic uremic syndrome (aHUS). We report final results from the largest prospective, observational, multicenter study of patients with aHUS treated with eculizumab.

METHODS

Patients with aHUS who participated in any of five parent eculizumab trials and received at least one eculizumab infusion were eligible for enrollment in a long-term follow-up study. Rates of thrombotic microangiopathy (TMA) manifestations off versus on eculizumab were evaluated. Additional endpoints included change from baseline estimated glomerular filtration rate (eGFR), long-term renal outcomes, and serious targeted treatment-emergent adverse events.

RESULTS

Among 93 patients (0-80 years of age), 51 (55%) remained on eculizumab and 42 (45%) discontinued; for those who discontinued, 21 (50%) reinitiated therapy. Patients who reinitiated eculizumab had similar baseline clinical characteristics to patients who remained on eculizumab, with higher likelihood of genetic/autoimmune complement abnormalities, more prior TMAs, and longer disease course versus those who did not reinitiate. Mean eGFR improved rapidly and remained stable for up to 6 years on eculizumab. In patients who discontinued, there was a trend toward decreasing renal function over time from discontinuation. Additionally, off-treatment TMA manifestation rates were higher in those aged < 18 years at diagnosis, with identified genetic/autoimmune complement abnormalities, or history of multiple TMAs prior to eculizumab initiation. The safety profile was consistent with previous studies. Three definite and one possible meningococcal infections related to eculizumab were reported and resolved with treatment. Three deaths unrelated to eculizumab were reported.

CONCLUSIONS

The current study confirms the efficacy and safety of eculizumab in aHUS, particularly with regard to long-term renal function and TMA events. Pediatric age at disease onset and presence of genetic or autoimmune complement abnormalities are risk factors for TMA events off treatment. Overall, patients who discontinue eculizumab may be at risk for additional TMA manifestations and renal function decreases. Discontinuation of eculizumab, with careful monitoring, is an option in select patients with consideration of patient preference, organ function normalization, and risk factors for relapse, including mutational analysis, age of onset, and history of multiple TMA episodes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01522170 , January 31, 2012.

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.