Atypical hemolytic uremic syndrome in the setting of complement-amplifying conditions: case reports and a review of the evidence for treatment with eculizumab

Characterization of patients with aHUS and associated triggers or clinical conditions: A Global aHUS Registry analysis

INTRODUCTION

Atypical haemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) associated with complement dysregulation; aHUS may be associated with other 'triggers' or 'clinical conditions'. This study aimed to characterize this patient population using data from the Global aHUS Registry, the largest collection of real-world data on patients with aHUS.

METHODS

Patients enrolled in the Global aHUS Registry between April 2012 and June 2021 and with recorded aHUS-associated triggers or clinical conditions prior/up to aHUS onset were analysed. aHUS was diagnosed by the treating physician. Data were classified by age at onset of aHUS (< or ≥18 years) and additionally by the presence/absence of identified pathogenic complement genetic variant(s) and/or anti-complement factor H (CFH) antibodies. Genetically/immunologically untested patients were excluded.

RESULTS

1947 patients were enrolled in the Global aHUS Registry by June 2021, and 349 (17.9%) met inclusion criteria. 307/349 patients (88.0%) had a single associated trigger or clinical condition and were included in the primary analysis. Malignancy was most common (58/307, 18.9%), followed by pregnancy and acute infections (both 53/307, 17.3%). Patients with an associated trigger or clinical condition were generally more likely to be adults at aHUS onset.

CONCLUSION

Our analysis suggests that aHUS-associated triggers or clinical conditions may be organized into clinically relevant categories, and their presence does not exclude the concurrent presence of pathogenic complement genetic variants and/or anti-CFH antibodies. Considering a diagnosis of aHUS with associated triggers or clinical conditions in patients presenting with TMA may allow faster and more appropriate treatment.

HELLP Syndrome and Differential Diagnosis with Other Thrombotic Microangiopathies in Pregnancy

Thrombotic microangiopathies (TMAs) comprise a distinct group of diseases with different manifestations that can occur in both pediatric and adult patients. They can be hereditary or acquired, with subtle onset or a rapidly progressive course, and they are particularly known for their morbidity and mortality. Pregnancy is a high-risk time for the development of several types of thrombotic microangiopathies. The three major syndromes are hemolysis, elevated liver function tests, and low platelets (HELLP); hemolytic uremic syndrome (HUS); and thrombotic thrombocytopenic purpura (TTP). Because of their rarity, clinical information and therapeutic results related to these conditions are often obtained from case reports, small series, registries, and reviews. The collection of individual observations, the evolution of diagnostic laboratories that have identified autoimmune and/or genetic abnormalities using von Willebrand factor post-secretion processing or genetic-functional alterations in the regulation of alternative complement pathways in some of these TMAs, and, most importantly, the introduction of advanced treatments, have enabled the preservation of affected organs and improved survival rates. Although TMAs may show different etiopathogenesis routes, they all show the presence of pathological lesions, which are characterized by endothelial damage and the formation of thrombi rich in platelets at the microvascular level, as a common denominator, and thrombotic damage to microcirculation pathways induces "mechanical" (microangiopathic) hemolytic anemia, the consumption of platelets, and ischemic organ damage. In this review, we highlight the current knowledge about the diagnosis and management of these complications during pregnancy.

Epidemiology, Management, and Outcome of Atypical Hemolytic Uremic Syndrome in an Omani Cohort

Objectives

Atypical hemolytic uremic syndrome (aHUS) is a rare, life-threatening disease of chronic uncontrolled complement pathway activation that leads to thrombotic-microangiopathy, along with severe organ damage, including end-stage kidney disease. This study aimed to evaluate the epidemiology, management, and outcome of aHUS in an Omani population.

Methods

This retrospective descriptive cohort study assessed all cases of aHUS diagnosed and followed up at two tertiary care centers in Oman from January 2008 to December 2019, based on clinical features, complement pathway assays, histopathological, and genetic testing.

Results

The study accrued 19 patients who fulfilled the inclusion criteria, of whom 11 (57.9%) were male. The participants' median age was 25.0 years (range = 0.1-69.0). Most (15; 78.9%) patients presented in the acute phase of the disease. The triad of hemolytic anemia, acute kidney injury, and thrombocytopenia was present in all patients. A trigger factor (e.g., infection) was identified in 68.4% of cases. Of the 14 (73.7%) patients who underwent kidney biopsy, 10 (71.4%) were found to have aHUS in native kidneys and three in grafted kidneys. Of the 11 (57.9%) patients who underwent genetic analysis, five (45.5%) were found to have a known pathogenic variant in their aHUS susceptibility genes. Plasma exchange followed by eculizumab was the treatment method in 11 (57.9%) cases. Complete renal recovery was achieved in seven (36.8%) patients, while four (21.1%) passed away during the study period.

Conclusions

The wide spectrum and multiple expressions of aHUS make it a challenge to diagnose and consequently may delay the commencement of the targeted treatment. Eculizumab is considered the first-line therapy and should be commenced as early as possible.

Treatment preference and quality of life impact: ravulizumab vs eculizumab for atypical hemolytic uremic syndrome

Aim: Ravulizumab and eculizumab are complement C5 inhibitors approved for the treatment of atypical hemolytic uremic syndrome (aHUS). Ravulizumab requires less frequent infusions than eculizumab, which may reduce treatment burden. This study investigated patients' treatment preferences and the impact of both treatments on patient and caregiver quality of life. Materials & methods: Two surveys were conducted (one for adult patients with aHUS and one for caregivers of pediatric patients with aHUS) to quantitatively assess treatment preference and the patient- and caregiver-reported impact of ravulizumab and eculizumab on quality of life. Patients were required to have a diagnosis of aHUS, to be currently receiving treatment with ravulizumab and to have received prior treatment with eculizumab. Participants were recruited via various sources: the Alexion OneSource™ patient support program, the Rare Patient Voice recruitment agency, the aHUS Foundation and directly via a clinician involved in the study. Results: In total, 50 adult patients (mean age: 46.5 years) and 16 caregivers of pediatric patients (mean age: 10.1 years) completed the surveys. Most adult patients (94.0%) and all caregivers reported an overall preference for ravulizumab over eculizumab; infusion frequency was one of the main factors for patients when selecting their preferred treatment. Fewer patients reported disruption to daily life and the ability to go to work/school due to ravulizumab infusion frequency (4.0% and 5.7%, respectively) than eculizumab infusion frequency (72.0% and 60.0%), with similar results for caregivers. Conclusion: Adult patients and caregivers of pediatric patients indicated an overall preference for ravulizumab than eculizumab for the treatment of aHUS, driven primarily by infusion frequency. This study contributes to the emerging real-world evidence on the treatment impact and preference in patients with aHUS.

Complement therapeutics are coming of age in rheumatology

The complement system was described over 100 years ago, and it is well established that activation of this pathway accompanies the great majority of autoimmune and inflammatory diseases. In addition, over three decades of work in murine models of human disease have nearly universally demonstrated that complement activation is upstream of tissue injury and the engagement of pro-inflammatory mechanisms such as the elaboration of cytokines and chemokines, as well as myeloid cell recruitment and activation. With that background, and taking advantage of advances in the development of biologic and small-molecule therapeutics, the creation and clinical evaluation of complement therapeutics is now rapidly expanding. This article reviews the current state of the complement therapeutics field, with a focus on their use in diseases cared for or consulted upon by rheumatologists. Included is an overview of the activation mechanisms and components of the system, in addition to the mechanisms by which the complement system interacts with other immune system constituents. The various therapeutic approaches to modulating the system in rheumatic and autoimmune diseases are reviewed. To understand how best to clinically assess the complement system, methods of its evaluation are described. Finally, next-generation therapeutic and diagnostic advances that can be envisioned for the future are discussed.

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).

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL TRIALS REGISTRATION

NCT02949128, ClinicalTrials.gov.

A Life-Threating Postpartum Atypical Hemolytic-Uremic Syndrome with Multiorgan Involvement

Atypical Hemolytic Uremic Syndrome is a very rare condition that can be triggered in predisposed patients. It can remain undiagnosed and can result in a life-threatening event or permanent renal failure. We report a case of a 36-year-old pregnant woman who developed atypical hemolytic uremic syndrome postpartum. She underwent an emergency caesarean section due to abruptio placenta, and she developed biochemical alterations suggestive of a thrombotic microangiopathy. Due to worsening of renal function after plasma exchange therapy, we decided to start therapy with eculizumab. Therapy was carried out with a weekly dose of 900 mg IV for five weeks. An improvement of clinical and biochemical parameters was rapidly observed, and her renal function completely recovered. The therapy was continued for six months, with a dose of 1200 mg of eculizumab every two weeks. One year after discontinuation of the therapy, her blood pressure and renal function were still normal. Our case confirms that it is important to promptly identify a pregnancy-related thrombotic microangiopathy and that early therapy can be life-saving for the patient and can preserve renal function, avoiding dialysis.

Pregnancy associated atypical hemolytic uremic syndrome presenting with preeclampsia with HELLP syndrome and following treatment with Eculizumab

Objectives

Pregnancy associated atypical hemolytic uremic syndrome (p-aHUS) is a rare condition of thrombotic microangiopathy (TMA) which causes an increase of fetal and maternal morbidity and mortality. It presents typically with a triad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia and acute progressive renal failure. Differential diagnoses of HELLP (Hemolysis, Elevated Liver enzymes, and Low Platelets) syndrome, preeclampsia, thrombotic thrombocytopenic purpura (TTP), and disseminated intravascular coagulation (DIC) syndrome must be considered. In the following case report, presented is a 32-year-old, 38 weeks pregnant Caucasian woman admitted to Eberswalde Hospital with signs of preeclampsia and HELLP Syndrome. Caesarean Section was performed due to HELLP syndrome and fetal distress. Acute renal failure occurs shortly after a successful delivery. After a diagnosis of p-aHUS is established, the patient was given Eculizumab, which yielded significant improvements.

Case presentation

A 32-year-old, 38 week pregnant Caucasian woman was admitted to Eberswalde Hospital with upper right abdominal pain. After a laboratory examination, a diagnosis of HELLP syndrome was established and a Caesarean Section was performed. The follow-up examination revealed deterioration of clinical signs with the patient experiencing dyspnea, oliguria, and oedema, as well as aggravation of laboratory values, ranging from severe thrombocytopenia, hemolytic anemia, liver injury, and acute kidney injury. After excluding other possible causes of TMA, a diagnosis of p-aHUS was established and a treatment with Eculizumab was administered. Clinical and laboratory signs of hemolysis and kidney functions were found to improve gradually after two administrations of Eculizumab. The patient was discharged after 20 days of hospitalization with significantly improved condition and hematological values.

Conclusions

A successful treatment of p-aHUS requires a comprehensive assessment and a prompt diagnosis, which can be confounded by multiple similar differential diagnoses. Treatment with Eculizumab was found to significantly improve the outcome of the patient, but more studies are required to decide on a standardized regiment for p-aHUS.

Kidney Involvement in Systemic Sclerosis

Background: Systemic sclerosis is a chronic multisystem autoimmune disease, characterized by diffuse fibrosis and abnormalities of microcirculation and small arterioles in the skin, joints and visceral organs. Material and Methods: We searched for the relevant articles on systemic sclerosis and kidney involvement in systemic sclerosis in the NIH library of medicine, transplant, rheumatologic and nephrological journals. Results: Half of patients with systemic sclerosis have clinical evidence of kidney involvement. Scleroderma renal crisis represents the most specific and serious renal event associated with this condition. It is characterized by an abrupt onset of moderate to marked hypertension and kidney failure. Early and aggressive treatment is mandatory to prevent irreversible organ damage and death. The advent of ACE-inhibitors revolutionized the management of scleroderma renal crisis. However, the outcomes of this serious complication are still poor, and between 20 to 50% of patients progress to end stage renal disease. Conclusions: Scleroderma renal crisis still represents a serious and life-threatening event. Thus, further studies on its prevention and on new therapeutic strategies should be encouraged.

Atypical hemolytic uremic syndrome after myomectomy: A case report

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy due to inability to regulate the complement cascade, resulting in thrombocytopenia, intravascular hemolysis, and end-organ damage. Over 70% of cases are associated with mutations in complement or complement regulatory proteins, and some two-thirds have recognized complement-activating conditions triggering an aHUS event. We describe a case of aHUS after abdominal myomectomy in a 42-year-old woman that was managed with plasma exchange and eculizumab (an anti-C5 monoclonal antibody). The diagnosis was confirmed by biopsy of normal-appearing deltoid skin that demonstrated microvascular C5b-9 deposition, diagnostic of systemic complement pathway activation. Although extremely uncommon following gynecologic surgery, aHUS should be considered in the setting of postoperative oliguric acute kidney injury, as prompt diagnosis is necessary to prevent significant morbidity and mortality.

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Thrombotic microangiopathy is a potentially lethal complication of myomectomy.

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Atypical hemolytic uremic syndrome following surgery has been rarely reported.

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Eculizumab is a life-saving treatment for atypical hemolytic uremic syndrome.

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Normal deltoid skin biopsy may support the diagnosis of complement deposition.

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This is a case of atypical hemolytic uremic syndrome after abdominal myomectomy.

A Rare Case of HELLP Syndrome with Hematomas of Spleen and Liver, Eclampsia, Severe Hypertension and Prolonged Coagulopathy-A Case Report

The HELLP syndrome (hemolysis, liver damage and thrombocytopenia) is a rare (0.5−0.9%) but serious complication of pregnancy or puerperium associated with a higher risk of maternal and fetal mortality and morbidity. Liver and spleen hematomas rarely entangle (<2%) HELLP cases, but rupture of the hematomas presents an immediate threat to life. We present the history of a 35-year old pregnant woman (at the 31st week) admitted to our hospital due to the risk of premature delivery. On the first day, the patient did not report any complains, and the only abnormality was thrombocytopenia 106 G/L. However, within several hours, tests showed platelet levels of 40.0 G/L, LDH 2862.0 U/L and AST 2051.6 U/L, and the woman was diagnosed with severe HELLP syndrome, complicated by hematomas of the liver and spleen, seizures (eclampsia), severe arterial hypertension and coagulation disorders. The purpose of this article is to highlight the need for early investigation of the causes of thrombocytopenia and the differentiation of HELLP from other thrombotic microangiopathies (TMAs).

Complement-Amplifying Conditions in Atypical Hemolytic Uremic Syndrome: A Canadian Case Series

Rationale

Thrombotic microangiopathies (TMAs) are systemic disorders that often affect the kidneys and encompass a heterogeneous group of conditions, including atypical hemolytic uremic syndrome (aHUS). The complement pathway is thought to play a crucial role in the pathogenesis of aHUS, and a favorable response can be obtained through complement C5 inhibition. There is emerging evidence to suggest that the same is also true for several other forms of TMA.

Objective

The purpose of this series is to report cases of aHUS in which both an innate defect of the alternative complement pathway and a complement-amplifying condition were suspected.

Methods

This case series describes 8 patients who were managed in Canadian tertiary centers for aHUS and who presented initially with complement-amplifying conditions.

Results

In all cases, aHUS was associated with organ dysfunction and in some, with an innate defect of the alternative complement pathway. The complement-amplifying conditions identified were diverse including immune disorders, pregnancy, and a Shiga toxin infection. Patients improved rapidly when treated with eculizumab or plasma exchange.

Conclusions

These observations illustrate the seriousness of secondary aHUS. They also add to existing lines of evidence that the complement pathway is potentially involved in this condition and that it should be considered as a therapeutic target of interest under such circumstances.

Atypical Hemolytic Uremic Syndrome Caused by a Rare Complement Factor B Mutation

Thrombotic microangiopathy (TMA), a rare and diagnostically challenging condition, commonly presents with a triad of thrombocytopenia, hemolytic anemia, and end-organ damage, such as renal failure. Most cases of the hemolytic uremic syndrome (HUS) are mediated by Shiga toxin-producing Escherichia coli, but some cases present as an atypical HUS, which includes thrombotic thrombocytopenic purpura and complement-mediated thrombotic microangiopathy (C-TMA). Although C-TMA occurs because of genetic and acquired mutations in the complement regulatory factors, it is usually hereditary. The currently available treatment options include therapeutic plasma exchange and administration of eculizumab, which is a monoclonal antibody against C5. Here, we report a diagnostically challenging and extremely rare case of a middle-aged Caucasian man who was diagnosed with atypical HUS that was caused by a mutation in complement factor B. This case highlights the importance of not overlooking rare causes of TMAs because the diagnostic evaluation is important for guiding appropriate management and obtaining a favorable prognosis.

Thrombotic Microangiopathy Syndromes-Common Ground and Distinct Frontiers

Thrombotic microangiopathies (TMAs) have in common a terminal phenotype of microangiopathic hemolytic anemia with end-organ dysfunction. Thrombotic thrombocytopenic purpura results from von Willebrand factor multimerization, Shiga toxin-mediated hemolytic uremic syndrome causes toxin-induced endothelial dysfunction, while atypical hemolytic uremic syndrome results from complement system dysregulation. Drug-induced TMA, rheumatological disease-induced TMA, and renal-limited TMA exist in an intermediate space that represents secondary complement activation and may overlap with atypical hemolytic uremic syndrome clinically. The existence of TMA without microangiopathic hemolytic features, renal-limited TMA, represents an undiscovered syndrome that responds incompletely and inconsistently to complement blockade. Hematopoietic stem cell transplant-TMA represents another more resistant form of TMA with different therapeutic needs and clinical course. It has become apparent that TMA syndromes are an emerging field in nephrology, rheumatology, and hematology. Much work remains in genetics, molecular biology, and therapeutics to unravel the puzzle of the relationships and distinctions apparent between the different subclasses of TMA syndromes.

Differentiating Hemolysis, Elevated Liver Enzymes, and Low Platelet Count Syndrome and Atypical Hemolytic Uremic Syndrome in the Postpartum Period

[Figure: see text].

Making the Correct Diagnosis in Thrombotic Microangiopathy: A Narrative Review

Purpose of review:

Thrombotic microangiopathy (TMA) is suspected in patients presenting with thrombocytopenia and evidence of a microangiopathic hemolytic anemia. Patients with TMA can be critically ill, so rapid and accurate identification of the underlying etiology is essential. Due to better insights into pathophysiology and causes of TMA, we can now categorize TMAs as thrombotic thrombocytopenic purpura, postinfectious (mainly Shiga toxin-producing Escherichia coli–induced) hemolytic uremic syndrome (HUS), TMA associated with a coexisting condition, or atypical HUS (aHUS). We recognized an unmet need in the medical community to guide the timely and accurate identification of TMA, the selection of tests to clarify its etiology, and the sequence of steps to initiate treatment.

Sources of information:

Key published studies relevant to the identification, classification, and treatment of TMAs in children or adults. These studies were obtained through literature searches conducted with PubMed or based on the prior knowledge of the authors.

Methods:

This review is the result of a consultation process that reflects the consensus of experts from Canada, the United States, and the United Arab Emirates. The members represent individuals who are clinicians, researchers, and teachers in pediatric and adult medicine from the fields of hematology, nephrology, and laboratory medicine. Authors, through an iterative review process identified and synthesized information from relevant published studies.

Key findings:

Thrombotic thrombocytopenic purpura occurs in the setting of insufficient activity of the von Willebrand factor protease known as ADAMTS13. Shiga toxin-producing Escherichia coli–induced hemolytic uremic syndrome, also known as “typical” HUS, is caused by gastrointestinal infections with bacteria that produce Shiga toxin (initially called verocytotoxin). A variety of clinical conditions or drug exposures can trigger TMA. Finally, aHUS occurs in the setting of inherited or acquired abnormalities in the alternative complement pathway leading to dysregulated complement activation, often following a triggering event such as an infection. It is possible to break the process of etiological diagnosis of TMA into 2 distinct steps. The first covers the initial presentation and diagnostic workup, including the processes of identifying the presence of TMA, appropriate initial tests and referrals, and empiric treatments when appropriate. The second step involves confirming the etiological diagnosis and moving to definitive treatment. For many forms of TMA, the ultimate response to therapies and the outcome of the patient depends on the rapid and accurate identification of the presence of TMA and then a standardized approach to seeking the etiological diagnosis. We present a structured approach to identifying the presence of TMA and steps to identifying the etiology including standardized lab panels. We emphasize the importance of early consultation with appropriate specialists in hematology and nephrology, as well as identification of whether the patient requires plasma exchange. Clinicians should consider appropriate empiric therapies while following the steps we have recommended toward definitive etiologic diagnosis and management of the TMA.

Limitations:

The evidence base for our recommendations consists of small clinical studies, case reports, and case series. They are generally not controlled or randomized and do not lend themselves to a stricter guideline-based methodology or a Grading of Recommendations Assessment, Development and Evaluation (GRADE)-based approach.

Management of thrombotic microangiopathy in pregnancy and postpartum: report from an international working group

Pregnancy and postpartum are high-risk periods for different forms of thrombotic microangiopathy (TMA). However, the management of pregnancy-associated TMA remains ill defined. This report, by an international multidisciplinary working group of obstetricians, nephrologists, hematologists, intensivists, neonatologists, and complement biologists, summarizes the current knowledge of these potentially severe disorders and proposes a practical clinical approach to diagnose and manage an episode of pregnancy-associated TMA. This approach takes into account the timing of TMA in pregnancy or postpartum, coexisting symptoms, first-line laboratory workup, and probability-based assessment of possible causes of pregnancy-associated TMA. Its aims are: to rule thrombotic thrombocytopenic purpura (TTP) in or out, with urgency, using ADAMTS13 activity testing; to consider alternative disorders with features of TMA (preeclampsia/eclampsia; hemolysis elevated liver enzymes low platelets syndrome; antiphospholipid syndrome); or, ultimately, to diagnose complement-mediated atypical hemolytic uremic syndrome (aHUS; a diagnosis of exclusion). Although they are rare, diagnosing TTP and aHUS associated with pregnancy, and postpartum, is paramount as both require urgent specific treatment.

Thrombotic microangiopathy versus class IV lupus nephritis in systemic lupus erythematosus

BACKGROUND

Kidney involvement is common in patients with systemic lupus erythematosus (SLE). This study investigates the clinical and prognostic characteristics of thrombotic microangiopathy (TMA) compared to class IV lupus nephritis in SLE patients.

METHODS

A retrospective review of patients who underwent kidney biopsy, with a primary diagnosis of SLE and TMA between June 2006 and September 2018 was conducted. Those patients were subsequently compared to patients with class IV lupus nephritis between January 2018 and December 2018. Demographics, laboratory, and serological data at the time of biopsy were abstracted.

RESULTS

Among 214 SLE patients records screened, 27 were included in the final analysis. Eight patients had lupus-related TMA without evidence of active lupus nephritis, while 19 patients had class IV lupus nephritis without evidence of TMA. TMA patients had significantly higher lactate dehydrogenase levels (718 ± 499 vs. 264 ± 107.7 U/L, p = 0.009), serum C3 (100.6 ± 39.3 vs. 65.8 ± 27 mg/dL, p = 0.049), white blood cell count (14743.8 ± 7933.3 vs. 5807.9 ± 2053.2 × 10E3/uL, p < 0.001), and total bilirubin (0.8 ± 0.5 vs. 0.3 ± 0.1 mg/dL, p = 0.007) in addition to significantly lower platelet counts (158.4 ± 88.6 vs. 240.3 ± 100.3 × 10E3/uL, p = 0.03), and haptoglobin (68.8 ± 116.1 vs. 166.8 ± 95.4 mg/dL, p = 0.03). After a median follow-up time of 53 weeks, 3 patients with TMA were dialysis-dependent (37.5%), compared with none in class IV lupus nephritis patients (p = 0.002).

CONCLUSIONS

TMA-associated SLE has worse prognosis compared to class IV lupus nephritis. An array of laboratory and pathological findings may be of value in discriminating between those two entities.

Post-traumatic thrombotic microangiopathy: What trauma surgeons need to know?

Thrombotic microangiopathy (TMA) is characterized by systemic microvascular thrombosis, target organ injury, anemia and thrombocytopenia. Thrombotic thrombocytopenic purpura, atypical hemolytic uremic syndrome and Shiga toxin E-coli-related hemolytic uremic syndrome are the three common forms of TMAs. Traditionally, TMA is encountered during pregnancy/postpartum period, malignant hypertension, systemic infections, malignancies, autoimmune disorders, etc. Recently, the patients presenting with trauma have been reported to suffer from TMA. TMA carries a high morbidity and mortality, and demands a prompt recognition and early intervention to limit the target organ injury. Because trauma surgeons are the first line of defense for patients presenting with trauma, the prompt recognition of TMA for these experts is critically important. Early treatment of post-traumatic TMA can help improve the patient outcomes, if the diagnosis is made early. The treatment of TMA is also different from acute blood loss anemia namely in that plasmapheresis is recommended rather than platelet transfusion. This article familiarizes trauma surgeons with TMA encountered in the context of trauma. Besides, it provides a simplified approach to establishing the diagnosis of TMA. Because trauma patients can require multiple transfusions, the development of disseminated intravascular coagulation must be considered. Therefore, the article also provides different features of disseminated intravascular coagulation and TMA. Finally, the article suggests practical points that can be readily applied to the management of these patients.

Association between thrombotic microangiopathy and activated alternative complement pathway in malignant nephrosclerosis

BACKGROUND

Malignant nephrosclerosis, defined as renal microangiopathy in the setting of severe hypertension, remains a critical renal emergency leading to end-stage renal disease despite aggressive anti-hypertensive treatment. Recently, activation of the complement alternative pathway (AP) has been reported to play a prominent role in the pathogenesis of malignant nephrosclerosis. However, subsequent study failed to recapitulate the findings of genetic complement abnormalities in the disease. This study aimed to determine the presence of AP activation and genetic complement defects and establish their correlations to renal microangiopathy lesions, clinical features and prognosis in patients with malignant nephrosclerosis.

METHODS

Fifty patients with malignant hypertension and concomitant thrombotic microangiopathy (TMA) proven by renal biopsy were investigated; 25 cases of kidney donors who received zero-hour allograft biopsies were used as normal controls. Various renal TMA lesions in patients with malignant nephrosclerosis were reviewed and evaluated using a semi-quantitative scoring system. Deposition of C5b-9, C3a, C5a, C4d and mannose-binding lectin was assessed by immunohistochemistry. Co-localization of C5b-9 and CD34 was detected by confocal microscopy. Complement factor B (FB), factor P (FP; properdin), factor D (FD), factor H (FH), C3a and C5a levels were quantified by enzyme-linked immonosorbent assay in plasma and urine samples of patients with malignant nephrosclerosis and controls. Genetic abnormalities of complement components were analysed by whole-exome sequencing.

RESULTS

Renal biopsies of malignant nephrosclerosis showed identical histopathological and ultrastructural features to atypical haemolytic uraemic syndrome. C5b-9, C3a and C5a deposits were found along the walls of arteries/arterioles and glomerular capillaries and localized in the endothelial cells. Elevated plasma and urinary levels of FB, FP, FD, C3a and C5a as well as decreased FH levels were observed in patients with malignant nephrosclerosis compared with normal controls. The urinary levels of complement AP components, but not the plasma levels, were correlated with renal functions, prognosis and active TMA lesions except for arteriolar thrombi. Finally, mutations of the MCP, CFB, CFH and CFHR5 genes were identified in 8 of 20 patients with malignant nephrosclerosis.

CONCLUSIONS

Aberrant complement AP dysregulation was demonstrated and associated with the activity, severity and renal outcomes of malignant nephrosclerosis. This observation warrants screening for complement defects in patients with malignant nephrosclerosis for the potential use of complement regulators and also highlights the need for further investigation of the precise role of AP in the pathogenesis of the disease.

Emerging Targeted Therapies for Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune, inflammatory disorder of the central nervous system that typically presents with recurrent episodes of optic neuritis, longitudinally extensive myelitis, brainstem, diencephalic, and cerebral syndromes. Up to 80% of NMOSD patients have a circulating pathogenic autoantibody that targets the water channel aquaporin-4 (AQP4-IgG). The discovery of AQP4-IgG transformed our understanding of the pathogenesis of the disease and its possible treatment targets. Monoclonal antibodies targeting terminal complement (eculizumab), CD19 (inebilizumab), and the interleukin-6 receptor (satralizumab) have demonstrated efficacy in NMOSD attack prevention in recent phase 3 trials and have gained subsequent regulatory approval in the USA and other countries. We aim to review the evidence supporting the efficacy of these new drugs.

Distinct genetic profile with recurrent population-specific missense variants in Korean adult atypical hemolytic uremic syndrome

INTRODUCTION

Atypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy (TMA), characterized by micro-angiopathic hemolytic anemia, thrombocytopenia, and renal failure. In more than half of cases, genetic defects leading to overactivation of the alternative complement system have been identified. In this study, we investigated genetic defects in Korean adult patients with aHUS.

MATERIALS AND METHODS

Sixty-six Korean adult patients with aHUS were ascertained from the Korean TMA Registry. Genetic variants of 15 aHUS-related genes (eight core genes [CFH, CFB, CFI, CD46, C3, THBD, PLG, and DGKE] and seven candidate genes [CFP, C4BPA, and CHFR1-5]) were analyzed from exome sequencing data. Multiplex ligation-dependent probe amplification of CFH and related genes was performed to detect hybrid genes or large deletions.

RESULTS

Thirty patients (45%) had at least one aHUS-related variant (s) in eight core genes (total 40 variant alleles). The most frequently affected gene was CFH (13/40, 32%), followed by THBD (8/40, 20%) and CD46 (7/40, 18%). The two most common variants were Asp486Tyr of THBD (N = 7) and Tyr1058His-Val1060Leu of CFH (N = 5, linked on the same allele), accounting for 30% (12/40). In seven candidate genes, 19 variants were detected. When combined, 40 patients (61%) had at least one variant in 15 core or candidate genes. No patients had anti-CFH Ab or hybrid gene/CFHR1 homozygous deletions.

CONCLUSIONS

The genetic profile of Korean adult aHUS was unique with recurrent missense variants, demonstrating ethnicity- and age-dependent differences in the genetic background of aHUS.

Complement in Secondary Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a condition characterized by thrombocytopenia and microangiopathic hemolytic anemia (MAHA) with varying degrees of organ damage in the setting of normal international normalized ratio and activated partial thromboplastin time. Complement has been implicated in the etiology of TMA, which are classified as primary TMA when genetic and acquired defects in complement proteins are the primary drivers of TMA (complement-mediated TMA or atypical hemolytic uremic syndrome, aHUS) or secondary TMA, when complement activation occurs in the context of other disease processes, such as infection, malignant hypertension, autoimmune disease, malignancy, transplantation, pregnancy, and drugs. It is important to recognize that this classification is not absolute because genetic variants in complement genes have been identified in patients with secondary TMA, and distinguishing complement/genetic-mediated TMA from secondary causes of TMA can be challenging and lead to potentially harmful delays in treatment. In this review, we focus on data supporting the involvement of complement in aHUS and in secondary forms of TMA associated with malignant hypertension, drugs, autoimmune diseases, pregnancy, and infections. In aHUS, genetic variants in complement genes are found in up to 60% of patients, whereas in the secondary forms, the finding of genetic defects is variable, ranging from almost 60% in TMA associated with malignant hypertension to less than 10% in drug-induced TMA. On the basis of these findings, a new approach to management of TMA is proposed.

Acute kidney injury during pregnancy leads to increased sFlt-1 and sEng and decreased renal T regulatory cells in pregnant rats with HELLP syndrome

BACKGROUND

The incidence of acute kidney injury (AKI) during pregnancy precedes a high maternal mortality rate of 20-40%. AKI during pregnancy has multiple etiologies; however, the more common are maternal hypertensive disorders, which include preeclampsia and HELLP (hemolysis, elevated liver enzyme, low platelet) syndrome. Therefore, we sought to assess the impact of AKI on blood pressure, kidney injury, and anti-angiogenic factors during pregnancies with and without HELLP syndrome.

METHODS

On gestational day (GD) 12, mini-osmotic pumps were inserted into a subset of normal pregnant (NP) rats infusing 4.7 μg/kg soluble fms-like tyrosine kinase-1 (sFlt-1) and 7 μg/kg soluble endoglin (sEng) to induce HELLP syndrome. On GD18, the renal pedicles were occluded for 45 min to induce AKI via bilateral ischemia reperfusion in a subset of NP (n = 18) or HELLP (n = 20) rats. Control NP (n = 20) and HELLP (n = 20) rats underwent a SHAM surgery on GD18. Plasma, urine, and maternal organs were saved for further analysis. Renal injury was assessed via renal histopathology, glomerular filtration rate (GFR), T cell infiltration, and assessment of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Data was measured via two-way analysis of variance with Tukey's test for post hoc analysis.

RESULTS

Blood pressures were increased in HELLP+AKI rats (p = 0.0001); both NP+AKI and HELLP+AKI rats had increased lactate dehydrogenase (p < 0.0001) and aspartate aminotransferase levels (p < 0.0001), and decreased platelet levels (p < 0.001) vs. NP rats. HELLP+AKI (p = 0.002) and HELLP rats (p = 0.0002) had evidence of renal fibrosis vs. NP rats. GFR was decreased in HELLP+AKI (p = 0.01) rats vs. NP rats. Urinary KIM-1 was increased in NP+AKI rats vs. NP (p = 0.003) and HELLP rats (p = 0.01). HELLP+AKI rats had increased urinary KIM-1 vs. NP (p = 0.0008) and HELLP rats (p = 0.004) and increased NGAL vs. HELLP rats (p = 0.002). HELLP+AKI rats had increased sFlt-1 (p = 0.009) vs. NP rats. NP+AKI (p = 0.02) and HELLP+AKI (p = 0.007) rats had increased sEng vs. NP rats. CD3+CD4+ T cells were significantly increased in HELLP+AKI rats vs. NP (p = 0.0002) and NP+AKI (p = 0.05) rats. T regulatory cells were significantly decreased in HELLP+AKI (p = 0.03) and NP+AKI (p = 0.02) rats vs. NP rats; there were no changes between groups in T helper 17 cells (p = 0.34).

CONCLUSION

The findings in this study suggest that AKI during pregnancy contributes to increased blood pressure and biochemical markers for HELLP syndrome, creates an anti-angiogenic imbalance, and exacerbates kidney injury as shown on histopathology, GFR, and kidney injury markers.

Renal disorders in rheumatologic diseases: the spectrum is changing (Part 1: connective tissue diseases)

The kidney is frequently involved by autoimmune rheumatic diseases. The renal manifestations may be variable, ranging from asymptomatic proteinuria and microscopic haematuria to nephrotic syndrome and rapidly progressive glomerulonephritis or vasculitis. In a number of cases the kidney involvement is related to the treatment of the original disease and may represent a major cause of morbidity and mortality. Thus, it is important for nephrologists and rheumatologists to remember that dysfunction of the kidney may be part of the primary systemic disorder or consequence of its pharmacotherapy. In the first part of this review we will analyse the kidney involvement in four autoimmune connective tissue diseases: systemic lupus erythematosus, Sjögren syndrome, polymyositis/dermatomyositis, and systemic sclerosis. Renal disease is common in lupus and is a main cause of morbidity and mortality. About 10% of patients with Sjögren syndrome may present interstitial nephritis or, more rarely, glomerulonephritis. Myoglobinuria and acute kidney injury is a frequent complication of polymyositis. Renal disease is one of the most serious complications of systemic sclerosis and may present with a dramatic renal crisis, characterized by malignant hypertension, oligo-anuria, and microangiopathic thrombocytopenic anaemia.

Innate and Adaptive Immune Responses in HELLP Syndrome

Innate and adaptive immune involvement in hemolysis, elevated liver enzymes and low platelet (HELLP) syndrome is an understudied field, although it is of high clinical importance. This syndrome implies a risk of serious morbidity and mortality to both the mother and the fetus during pregnancy. It was proposed that HELLP syndrome occurs in a circulatory inflammatory milieu, that might in turn participate in a complex interplay between the secreted inflammatory immunomodulators and immune cell surface receptors. Meanwhile, reported immune cell attenuation during HELLP may consequently lead to a prolonged immunoactivation and tissue damage. In this regard, learning more about the immune components of this syndrome should widen the understanding of the HELLP pathophysiology and eventually enable development of novel immune-based therapeutics. This review aims to summarize and discuss the recent and previous findings of the innate and adaptive immune responses during HELLP in order to update the current knowledge of the immune involvement in HELLP pathogenesis.

Pregnancy-Associated Atypical Hemolytic Uremic Syndrome: A Systematic Review

OBJECTIVE

To evaluate disease presentation, diagnosis, treatment, and clinical outcomes in pregnancy-associated atypical hemolytic uremic syndrome (aHUS).

DATA SOURCES

We searched PubMed, MEDLINE, Cochrane Library, ClinicalTrials.gov, Web of Science, EMBASE and Google Scholar, from inception until March 2018.

METHODS OF STUDY SELECTION

We included English-language articles describing aHUS in pregnancy or postpartum. The diagnosis of aHUS was characterized by hemolysis, thrombocytopenia, and renal failure and was distinguished from typical diarrhea-associated hemolytic uremic syndrome. Patients were excluded if individual data could not be obtained, the diagnosis was unclear, or an alternative etiology was more likely, such as thrombotic thrombocytopenic purpura or Shiga toxin-producing Escherichia coli. Reports were appraised by two reviewers, with disagreements adjudicated by a third reviewer.

TABULATION, INTEGRATION, AND RESULTS

The search identified 796 articles. After review of titles, abstracts, and full text, we identified 48 reports describing 60 unique cases of pregnancy-associated aHUS, with 66 pregnancies. Twelve cases involved pregnancy in women with known aHUS, and 54 cases involved first-episode pregnancy-associated aHUS. Women with known aHUS, particularly those with baseline creatinine at or above 1.5 mg/dL, had a high rate of adverse pregnancy outcomes. For first-episode pregnancy-associated aHUS, diagnosis most often occurred postpartum (94%), after a cesarean delivery (70%), in nulliparous women (58%). Preceding obstetric complications were common and included fetal death, preeclampsia, and hemorrhage. Diagnosis was usually made clinically, based on the triad of microangiopathic hemolysis, thrombocytopenia, and renal failure. Additional testing included renal biopsy, complement genetic testing, and ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) testing. Treatment modalities included corticosteroids, plasma exchange, dialysis, and eculizumab. More women with first-episode pregnancy-associated aHUS achieved disease remission when treated with eculizumab, compared with those not treated with eculizumab (88% vs 57%, P=.02).

CONCLUSION

Pregnancy-associated aHUS usually presents in the postpartum period, often after a pregnancy complication, and eculizumab is effective for achieving disease remission.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42019129266.

Atypical hemolytic uremic syndrome and complement blockade: established and emerging uses of complement inhibition

PURPOSE OF REVIEW

Atypical hemolytic uremic syndrome (aHUS) is a diagnosis that has captured the interest of specialists across multiple fields. The hallmark features of aHUS are microangiopathic hemolysis and thrombocytopenia, which creates a diagnostic dilemma because of the occurrence of these findings in a wide variety of clinical disorders.

RECENT FINDINGS

In most of the instances, aHUS is a diagnosis of exclusion after ruling out causes such as Shigella toxin, acquired or genetic a disintegrin and metalloproteinase thrombospondin motif 13 deficiency (thrombotic thrombocytopenic purpura), and vitamin B12 deficiency. In the purest sense, aHUS is a genetic condition that is activated (or unmasked) by an environmental exposure. However, it is now evident that complement activation is a feature of many diseases. Variants in complement regulatory genes predispose to microangiopathic hemolysis in many rheumatologic, oncologic, and drug-induced vascular, obstetric, peritransplant, and infectious syndromes.

SUMMARY

Many 'hemolysis syndromes' overlap clinically with aHUS, and we review the literature on the treatment of these conditions with complement inhibition. New reports on the treatment of C3 glomerulopathy, Shiga toxin-related classic hemolytic uremic syndrome, and medication-related thrombotic microangiopathy will be reviewed as well.

Complement and Renal Thrombotic Microangiopathy Associated With Hypertension and Scleroderma

Thrombotic microangiopathy is characterized by the presence of thrombocytopenia and microangiopathic hemolytic anemia and can occur in up to 50% of patients with hypertensive emergency and 10-15% with scleroderma. This review discusses the emerging role of complement in these 2 clinical entities. Specifically, we evaluate the evidence linking complement dysregulation with the manifestation of thrombotic microangiopathy and its clinical course in these settings. We also explore the rationale for complement blockade in these complex clinical scenarios that often have poor outcomes.

Acute Kidney Injury in Pregnancies Complicated With Preeclampsia or HELLP Syndrome

Acute kidney injury that occurs during pregnancy or in the post-partum period (PR-AKI) is a serious obstetric complication with risk of significant associated maternal and fetal morbidity and mortality. Recent data indicates that the incidence of PR-AKI is increasing, although accurate calculation is limited by the lack of a uniform diagnostic criteria that is validated in pregnancy. Hypertensive and thrombotic microangiopathic disorders of pregnancy have been identified as major contributors to the burden of PR-AKI. As is now accepted regarding preeclampsia, HELLP syndrome and atypical hemolytic uremic syndrome, it is believed that PR-AKI may have long-term renal, cardiovascular and neurocognitive consequences that persist beyond the post-partum period. Further research regarding PR-AKI could be advanced by the development of a pregnancy-specific validated definition and classification system; and the establishment of refined animal models that would allow researchers to further elucidate the mechanisms and sequelae of the disorder.

Eculizumab for Severe Thrombotic Microangiopathy Secondary to Surgical Invasive Stress and Bleeding

Atypical hemolytic uremic syndrome (aHUS) is an extremely rare condition caused by an excessive activation of the complement pathway based on genetic or acquired dysfunctions in complement regulation, leading to thrombotic microangiopathy (TMA). A complement-amplifying condition (CAC) can trigger aHUS occurrence along with complement abnormality. We herein report a case of severe TMA after laparoscopic myomectomy in a healthy woman. This case was eventually diagnosed as complement-mediated TMA secondary to surgical invasive stress as a CAC, with no definitive diagnosis of aHUS despite a genetic test. The patient fully recovered after several eculizumab administrations.

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.

Acute kidney injury secondary to thrombotic microangiopathy associated with idiopathic hypereosinophilic syndrome: a case report and review of the literature

Background

Renal involvement in idiopathic hypereosinophilic syndrome is uncommon. The mechanism of kidney damage can be explained as occurring via two distinct pathways: (1) thromboembolic ischemic changes secondary to endocardial disruption mediated by eosinophilic cytotoxicity to the myocardium and (2) direct eosinophilic cytotoxic effect to the kidney.

Case presentation

We present a case of a 63-year-old Caucasian man who presented to our hospital with 2 weeks of progressively generalized weakness. He was diagnosed with idiopathic hypereosinophilic syndrome with multiorgan involvement and acute kidney injury with biopsy-proven thrombotic microangiopathy. Full remission was achieved after 8 weeks of corticosteroid therapy.

Conclusion

Further studies are needed to investigate if age and absence of frank thrombocytopenia can serve as a prognostic feature of idiopathic hypereosinophilic syndrome, as seen in this case.

Complement Activation and Thrombotic Microangiopathies

BACKGROUND AND OBJECTIVES

Atypical hemolytic uremic syndrome is a form of thrombotic microangiopathy caused by dysregulation of the alternative complement pathway. There is evidence showing complement activation in other thrombotic microangiopathies. The aim of this study was to evaluate complement activation in different thrombotic microangiopathies and to monitor treatment response.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Complement activation was assessed by exposing endothelial cells to sera or activated-patient plasma-citrated plasma mixed with a control sera pool (1:1)-to analyze C5b-9 deposits by immunofluorescence. Patients with atypical hemolytic uremic syndrome (n=34) at different stages of the disease, HELLP syndrome (a pregnancy complication characterized by hemolysis, elevated liver enzymes, and low platelet count) or severe preeclampsia (n=10), and malignant hypertension (n=5) were included.

RESULTS

Acute phase atypical hemolytic uremic syndrome-activated plasma induced an increased C5b-9 deposition on endothelial cells. Standard and lower doses of eculizumab inhibited C5b-9 deposition in all patients with atypical hemolytic uremic syndrome, except in two who showed partial remission and clinical relapse. Significant fibrin formation was observed together with C5b-9 deposition. Results obtained using activated-plasma samples were more marked and reproducible than those obtained with sera. C5b-9 deposition was also increased with samples from patients with HELLP (all cases) and preeclampsia (90%) at disease onset. This increase was sustained in those with HELLP after 40 days, and levels normalized in patients with both HELLP and preeclampsia after 6-9 months. Complement activation in those with malignant hypertension was at control levels.

CONCLUSIONS

The proposed methodology identifies complement overactivation in patients with atypical hemolytic uremic syndrome at acute phase and in other diseases such as HELLP syndrome and preeclampsia. Moreover, it is sensitive enough to individually assess the efficiency of the C5 inhibition treatment.

Eculizumab and Beyond: The Past, Present, and Future of Complement Therapeutics

Dysregulation of the complement system underlies the pathophysiology of many diseases. Renewed interest in complement occurred with the recognition that its therapeutic inhibition was possible. Terminal complement blockade with the anti-C5 monoclonal antibody eculizumab significantly changed management and clinical outcomes of patients with paroxysmal nocturnal hemoglobinuria, and served as a proof of concept for other complement-mediated diseases. Eculizumab is also approved for atypical hemolytic uremic syndrome and myasthenia gravis. Multiple new disease indications have been identified, and novel complement inhibitors are in various stages of development, with several currently in human trials. Beyond C5, these new drugs block proximal complement, pathway-specific targets, convertase activity, and anaphylatoxin function. Though monoclonal antibodies are still common, peptides, RNAi, and small molecule inhibitors provide the opportunity for different administration routes and schedules. Several challenges still exist or will soon present themselves, including mitigation of infection risk, effective monitoring strategies, and how to choose between therapeutics when more than one is available. In this review, we will describe the lessons learned from the "eculizumab era," present many of the novel therapeutics currently or soon to be in trials, and highlight some of the challenges that will require attention as the field progresses.

Eculizumab treatment of thrombotic microangiopathy in a patient with ulcerative colitis

Secondary thrombotic microangiopathy (TMA) can be induced by several underlying conditions and drugs, yet coexistence of TMA and inflammatory bowel disease (IBD) has only infrequently been documented. A successful management beyond supportive care in cases with secondary TMA represents a challenge, as some underlying conditions might amplify complement dysregulation or even unmask a genetic predisposition to atypical hemolytic uremic syndrome (HUS)-both of which could require treatment with a complement blocking agent. We observed a case in which TMA developed in a patient with ulcerative colitis (UC). Genetic screening showed a heterozygous mutation in diacylglycerol kinase ε (DGKE). Eculizumab resulted in complete resolution of TMA, however UC relapsed after cessation of eculizumab.

Outcomes of Kidney Transplant Patients with Atypical Hemolytic Uremic Syndrome Treated with Eculizumab: A Systematic Review and Meta-Analysis

Background: Kidney transplantation in patients with atypical hemolytic uremic syndrome (aHUS) is frequently complicated by recurrence, resulting in thrombotic microangiopathy in the renal allograft and graft loss. We aimed to assess the use of eculizumab in the prevention and treatment of aHUS recurrence after kidney transplantation. Methods: Databases (MEDLINE, EMBASE and Cochrane Database) were searched through February 2019. Studies that reported outcomes of adult kidney transplant recipients with aHUS treated with eculizumab were included. Estimated incidence rates from the individual studies were extracted and combined using random-effects, generic inverse variance method of DerSimonian and Laird. Protocol for this systematic review has been registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018089438). Results: Eighteen studies (13 cohort studies and five case series) consisting of 380 adult kidney transplant patients with aHUS who received eculizumab for prevention and treatment of post-transplant aHUS recurrence were included in the analysis. Among patients who received prophylactic eculizumab, the pooled estimated incidence rates of recurrent thrombotic microangiopathy (TMA) after transplantation and allograft loss due to TMA were 6.3% (95%CI: 2.8–13.4%, I² = 0%) and 5.5% (95%CI: 2.9–10.0%, I² = 0%), respectively. Among those who received eculizumab for treatment of post-transplant aHUS recurrence, the pooled estimated rates of allograft loss due to TMA was 22.5% (95%CI: 13.6–34.8%, I² = 6%). When the meta-analysis was restricted to only cohort studies with data on genetic mutations associated with aHUS, the pooled estimated incidence of allograft loss due to TMA was 22.6% (95%CI: 13.2–36.0%, I² = 10%). We found no significant publication bias assessed by the funnel plots and Egger’s regression asymmetry test (p > 0.05 for all analyses). Conclusions: This study summarizes the outcomes observed with use of eculizumab for prevention and treatment of aHUS recurrence in kidney transplantation. Our results suggest a possible role for anti-C5 antibody therapy in the prevention and management of recurrent aHUS.

Relative incidence of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome in clinically suspected cases of thrombotic microangiopathy

Background

Data are lacking on the relative incidence of thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS) caused by Shiga toxin–producing Escherichia coli (STEC) and atypical HUS (aHUS) in patients presenting with thrombotic microangiopathies (TMAs).

Methods

This was a prospective, cross-sectional, multicentre and non-interventional epidemiological study. Patients fulfilling criteria for TMAs (platelet consumption, microangiopathic haemolytic anaemia and organ dysfunction) were included in the study. The primary objective was to assess the relative incidence of TTP, STEC-HUS, aHUS and ‘other’ physician-defined diagnoses. The secondary objective was to develop an algorithm to predict a severe deficiency in ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity (≤10%) using routine laboratory parameters. A post hoc classification using the recent Kidney Disease: Improving Global Outcomes diagnostic criteria was then undertaken to further classify patient groups.

Results

aHUS was diagnosed with a relative incidence of 61%, whereas TTP, STEC-HUS and ‘other’ were diagnosed in 13, 6 and 20% of patients, respectively. In the post hoc analysis, 27% of patients with a TMA were classified as ‘primary aHUS’ and 53% as ‘secondary aHUS’. Multivariate analysis revealed that severe deficiency in ADAMTS13 activity (≤10%) was unlikely to underlie TMA if platelet and serum creatinine were above threshold values of 30 × 10⁹/L and 1.8 mg/dL, respectively (negative predictive value of 92.3 and 98.1, respectively, if one or both values were above the threshold).

Conclusions

In this study, aHUS was the most common single diagnosis among patients presenting with a TMA. In the absence of an ADAMTS13 activity result, platelet count and serum creatinine may aid in the differential diagnosis.

The Extended Use of Eculizumab in Pregnancy and Complement Activation⁻Associated Diseases Affecting Maternal, Fetal and Neonatal Kidneys-The Future Is Now?

Excessive complement activation is involved in the pathogenesis of many diseases and the kidney is an organ with particular susceptibility to complement-mediated injury. Apart from paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS), there are several other diseases with clear evidence of complement activation affecting both maternal and fetal kidneys during pregnancy and causing long-term adverse outcomes. Several novel drugs have been recently developed for blocking the complement cascade, including purified plasma proteins, new monoclonal antibodies, recombinant proteins, small molecules, and small interfering RNA agents. Eculizumab, the humanized monoclonal IgG2/4-antibody targeting C5 was approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for treatment of two rare diseases: PNH in 2007 and aHUS in 2011. There is an increasing number of publications of successful use of eculizumab for off-label indications, e.g., in pregnant women with antiphospholipid syndrome, sickle-cell anemia, and HELLP syndrome. These severe diseases are associated with both high maternal and fetal morbidity and mortality rate and substantial prematurity. Eculizumab has considerably improved overall outcome of patients with PNH and aHUS, enabling safe pregnancy for many women. Prolongation of pregnancy and the use of eculizumab, even for only a few weeks, may protect not only maternal renal function, but also alleviate acute and long-term renal consequences of prematurity in offspring.

Recurrent case of pregnancy-induced atypical haemolytic uremic syndrome (P-aHUS)

Pregnancy-induced atypical haemolytic uremic syndrome (P-aHUS) is a rare condition characterised by microangiopathic haemolytic anaemia, thrombocytopenia and renal failure. It accounts for approximately 7% of total HUS cases. Here, we present a case of recurrent P-aHUS in a 25-year-old Hispanic woman. Pregnancy was the clear trigger in both instances, and the disease manifested in first week of the postpartum period. Because of her significant obstetric history, a multidisciplinary approach was adopted to monitor her second pregnancy antepartum and post partum. As the patient developed recurrence of P-aHUS 4 days after her delivery, she was immediately administered eculizumab within few hours of disease manifestation. The patient normalised her haematological parameters within 1 week but sustained dialysis-requiring renal failure for a total of 6 weeks. This case highlights the advances as well as the ongoing uncertainties, especially with respect to the use of eculizumab, in this rare but morbid disease.

Where are we with haemolytic uremic syndrome?

Haemolytic uremic syndrome (HUS) is characterised by microangiopathic haemolytic anaemia with acute kidney injury. It is currently classified into two main categories: Shiga-toxin producing E. coli-hemolytic uremic syndrome (STEC-HUS) and atypical haemolytic uremic syndrome (aHUS). Endothelial cell damage is the common pathway in HUS to developing thrombotic microangiopathy. Atypical HUS includes primary, secondary and aHUS due to metabolic diseases. In the majority of aHUS cases, hyperactivity of the alternative complement pathway plays a central role. Therefore, treatment is based on complement inhibitors like eculizumab, a drug that has revolutionised the natural history of the disease. Relapses are frequent after kidney transplant and thus confer a poor prognosis.

Hemolytic-uremic syndrome after Escherichia coli urinary tract infection in humans: systematic review of the literature

BACKGROUND

Intestinal infections caused by a shigatoxin-positive Escherichia coli (mostly of the serogroups O26, O45, O103, O111, O121, O145 and especially O157) are a common cause of hemolytic-uremic syndrome. Hemolytic-uremic syndrome was first linked with an E. coli urinary tract infection 40 years ago.

METHODS

We conducted a systematic review of the literature addressing the association between E. coli urinary tract infection and hemolytic-uremic syndrome.

RESULTS

For the final analysis, we retained 23 original reports published since 1979. Five unselected pediatric case series addressed the possible occurrence of hemolytic-uremic syndrome after an acute symptomatic E. coli urinary tract infection among 266 cases and found the mentioned association in 8 (3.0%) cases. We also found 28 individual cases (17 females and 11 males) of hemolytic-uremic syndrome preceded by an E. coli urinary tract infection: 16 children aged from 2 days to 6.0 years and 12 adults aged from 22 to 75 years. Testing for shigatoxin, performed in 19 cases, was positive in 15 cases. E. coli serotyping was performed in 18 cases: testing for serotype O157, O103 and O145 was positive in one, one and two cases, respectively, while testing for serotype O26, O45, O111 and O121 was always negative.

CONCLUSIONS

Hemolytic-uremic syndrome rarely occurs after an acute E. coli urinary tract infection. It affects both children and adults and is mostly caused by germs that are shigatoxin-positive.

Adults with septic shock and extreme hyperferritinemia exhibit pathogenic immune variation

Post-hoc subgroup analysis of the negative trial of interleukin-1β receptor antagonist (IL1RA) for septic shock suggested that patients with features of macrophage activation syndrome (MAS) experienced a 50% relative risk reduction for mortality with treatment. Here we seek a genetic basis for this differential response. From 1341 patients enrolled in the ProCESS trial of early goal directed therapy for septic shock, we selected 6 patients with MAS features and the highest ferritin, for whole exome sequencing (mean 24,030.7 ηg/ml, +/SEM 7,411.1). Eleven rare (minor allele frequency <5%) pathogenic or likely pathogenic variants causal for the monogenic disorders of Familial Hemophagocytic Lymphohistiocytosis, atypical Hemolytic Uremic Syndrome, Familial Mediterranean Fever, and Cryopyrin-associated Periodic Fever were identified. In these conditions, seven of the identified variants are currently targeted with IL1RA and four with anti-C5 antibody. Gene-targeted precision medicine may benefit this subgroup of patients with septic shock and pathogenic immune variation.