Atypical Hemolytic Uremic Syndrome Research Articles

Shiga toxin-producing Escherichia coli infection as a precipitating factor for atypical hemolytic-uremic syndrome.

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy characterized by intravascular hemolysis. It can be classified as either typical, primarily caused by Shiga toxin-producing Escherichia coli (STEC) infection, or as atypical HUS (aHUS), which results from uncontrolled complement activation. We report the case of a 9-year-old boy with aHUS due to compound heterozygous complement factor H-related genes (CFHR) 1/3 and CFHR1-CFHR4 deletions, leading to the development of anti-complement factor H (CFH) autoantibodies. The patient presented nephrological and neurological thrombotic microangiopathy with STEC positivity. Additionally, we provide an extensive literature review of aHUS cases initially classified as typical. A total of 11 patients were included, 73% of whom were pediatric. Kidney replacement therapy was required in 73% of patients. The recurrence rate was 55%. All cases were found positive for pathological variants of the complement system genes. The most commonly implicated gene was CFH, while the CFHR genes were involved in 36% of cases, although none exhibited anti-CFH autoantibodies. Anti-complement therapy was administered in 54% of cases, and none of the patients who received it early progressed to kidney failure. STEC infection does not exclude aHUS diagnosis, and early use of anti-complement therapy might be reasonable in life-threatening conditions. Genetic testing can be helpful in patients with atypical presentations and can confirm the necessity of prolonged anti-complement therapy.

Thrombotic Microangiopathy in the Postpartum Period (Literature Review, Clinical Case Report)

Introduction. Thrombotic microangiopathy (TMA) is a heterogeneous group of diseases that, in the presence of endothelial damage, can lead to microvascular thrombosis, secondary platelet consumption, mechanical hemolysis and ischemic end-organs damage. Such triad of symptoms as acute kidney injury (AKI), microangiopathic hemolysis and thrombocytopenia may also accompany some pregnancy-specific conditions (severe preeclampsia/HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), acute fatty liver disease of pregnancy (AFLP), and conditions not related to pregnancy, but triggered by it (catastrophic antiphospholipid syndrome (CAPS), lupus flare. The aim of the study. To review the current literature devoted to the problem of thrombotic microangiopathy, to demonstrate on a clinical case a step-by-step differentiated approach to the diagnosis of the type of thrombotic microangiopathy causing acute kidney injury in the postpartum period, and to describe modern methods of treatment of these diseases. Results. The classical types of TMA are thrombotic thrombocytopenic purpura (TTP) and typical hemolytic uremic syndrome (HUS), also known as enterohemorrhagic Shiga toxin-producing Escherichia coli (STEC)-associated HUS (STEC-HUS). Pathophysiologically, all forms of TMA involve complement-mediated endothelial cell damage, which mainly affects the capillary zone of the kidney. Pregnancy can trigger atypical HUS (aHUS) or TTP. The article describes the clinical case of a 37-year-old woman who developed AKI following a complicated delivery. A turn-based differential diagnosis of aHUS was performed. Unwarranted discontinuation of the targeted therapy with Eculisumab led to the development of chronic renal failure Conclusions. Thrombotics microangiopathy are the life-threatening conditions rarely seen in pregnancy making its early recognition difficult. As thrombotics microangiopathy require urgent treatment, plasmapheresis should be started as soon as they are suspected, followed by targeted therapy (Eculisumab, Rituximab) after the confirmation of the diagnosis. This may contribute to reducing maternal morbidity and mortality rates.

Meningococcal Carriage in Children with Atypical Hemolytic Uremic Syndrome Receiving Eculizumab Therapy.

Eculizumab is a first-line treatment for atypical hemolytic uremic syndrome (aHUS), and patients undergoing eculizumab therapy may become more susceptible to infection caused by Neisseria meningitidis (Nm). While meningococcal vaccination is required for patients undergoing eculizumab therapy, there is limited knowledge about meningococcal carriage in children with aHUS. We aimed to evaluate (1) the prevalence of Nm carriage, (2) serogroup distribution, and (3) the immunization status of children undergoing eculizumab treatment for aHUS. The Meningo-aHUS study is a prospective, multi-center study evaluating meningococcal carriage in children and adolescents in Türkiye receiving eculizumab for aHUS. We noted the age, gender, daycare, school, or university attendance, passive smoking status, previous infection and antibiotic use, and previous immunization history, including meningococcal vaccines, from the medical records of those children with aHUS. We collected nasopharyngeal samples, tested them for Nm using real-time polymerase chain reaction, and performed a serogroup analysis on the positive samples. We collected nasopharyngeal samples from 62 children with aHUS. Out of 62 children, 61 (98.4%) had received at least one dose of the meningococcal vaccine. The median time since the last meningococcal vaccine dose was 15 months (1-59 months). We detected meningococcal carriage in three (4.8%, 95% CI 1.0-13.5) children, and all three strains were non-groupable (NG). No other serogroups were detected. Almost all the children received their risk-group meningococcal immunization, including booster doses. A 4.8% of children with aHUS carried NG meningococci and, no vaccine serogroups were detected. Patients treated with eculizumab remain profoundly susceptible to IMD due to these NG meningococcal strains. The occurrence of breakthrough cases and carriage of Nm, especially NG strains, highlights the significance of maintaining a state of constant alertness, promptly seeking medical attention, and swiftly treating any symptoms that align with IMD, regardless of their vaccination status or antibiotic prophylaxis.

Hypogammaglobulinemia in a child with atypical hemolytic-uremic syndrome

We present a unique clinical case of an atypical hemolytic-uremic syndrome in a child. The mutation in exon 6 of the CD46 gene (chr1:207940532G>C) leads to a homozygous or hemizygous missense substitution. An 8-year-old girl was urgently hospitalized with symptoms of hemorrhagic syndrome and acute kidney injury. The child from the second pregnancy with an aggravated obstetric anamnesis, the first operative labor at the 38th week, who has an aggravated genealogical anamnesis. Initially, the disease developed in the guise of gastroenterological pathology: the girl had dyspeptic disorders, most likely associated with pathology of carbohydrate metabolism, also frequent infectious diseases and a lag in physical development. From the age of 4 years, the girl suffered from persistent hypoalbuminemia, hypoproteinemia and hypogammaglobulinemia, requiring replacement therapy with intravenous immunoglobulins. She was repeatedly examined in gastroenterological departments in Yekaterinburg and Moscow in 2021-2023, but no data concerning protein-losing enteropathies or primary immunodeficiency was obtained. Also, the whole-exome sequencing with result validation hasn’t confirmed an inherited etiology of the presumed congenital immune error. However, a CD46 gene mutation, associated with the development of hemolytic-uremic syndrome in some publications, was identified in the study. The signs of thrombotic microangiopathy were preceded by fever of unspecified etiology: microangiopathic hemolysis, thrombocytopenia, hyperazotemia, C3 consumption, proteinuria, and macrohematuria; hypercholesterolemia, protein metabolism disorder, increased transaminases, ferritin were also noted. According to the ultrasound of the kidneys there were diffuse changes in the parenchyma, decreased velocity indices of blood flow in both renal arteries at all levels. Differential diagnosis was carried out with thrombotic thrombocytopenic purpura, autoimmune hemolytic anemia, antinuclear form of atypical hemolytic-uremic syndrome, viral and bacterial infections, systemic pathology, antiphospholipid syndrome, and hemoblastosis. The girl didn’t need a renal replacement therapy. When complement-blocking therapy with eculizumab was initiated on vital indications, the signs of the disease were gradually eliminated. The prolonged absence of nephropathy in the child may indicate the diversity of the CD46 gene’s functions and different phenotypic manifestation of its mutations. Analysis of literature sources and detection of CD46 “environment” genes (CYBA, LYST, ARPCIB) by full-exome sequencing suggest ambiguity and polymorphism of phenotypic manifestations of complement-mediated mutation.

Atypical haemolytic uremic syndrome

Atypical haemolytic uremic syndrome

An expert discussion on the atypical hemolytic uremic syndrome nomenclature—identifying a road map to precision: a report of a National Kidney Foundation Working Group

The term atypical hemolytic uremic syndrome has been in use since the mid-1970s. It was initially used to describe the familial or sporadic form of hemolytic uremic syndrome as opposed to the epidemic, typical form of the disease. Over time, the atypical hemolytic uremic syndrome term has evolved into being used to refer to anything that is not Shiga toxin-associated hemolytic uremic syndrome. The term describes a heterogeneous group of diseases of disparate causes, a circumstance that makes defining disease-specific natural history and/or targeted treatment approaches challenging. A working group of specialty-specific experts in the thrombotic microangiopathies was convened to review the validity of this broad term in an era of swiftly advancing science and targeted therapeutics. A Delphi approach was used to define and interrogate some of the key issues related to the atypical hemolytic uremic syndrome nomenclature.

The utility of the normal thin section skin biopsy in the assessment of systemic/extracutaneous disease and small fiber neuropathy

Diseases reflective of multiorgan vascular injury of diverse etiology, peripheral nerve disease, dysautonomia syndromes, and intravascular lymphoma may exhibit abnormalities on a normal skin biopsy that may be instrumental in establishing a diagnosis. A retrospective review of our database was conducted to uncover cases where a normal skin biopsy was performed to rule in or out such systemic diseases as complement-driven thrombotic microvascular disease (including atypical hemolytic uremic syndrome, posttransplant thrombotic microangiopathy, and severe or critical COVID-19), systemic capillary leak syndrome, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) intravascular B cell lymphoma, small fiber neuropathy, dysautonomia syndromes, and mast cell activation syndrome. Among the special studies were immunohistochemical staining to detect C5b-9, CD56, and myxovirus resistance protein A, as well as mast cell, B and T cell markers. Characteristic patterns were critical in establishing diagnoses such as : increased C5b-9 microvascular deposition in the deltoid area (atypical hemolytic uremic syndrome, posttransplant thrombotic microangiopathy, catastrophic antiphospholipid antibody syndrome, and severe or critical COVID-19); enhanced type I interferon signaling (systemic capillary leak syndrome); ultrastructural arteriopathic changes (CADASIL); reduced cutaneous autonomic innervation in the lower extremities (small fiber neuropathy and postural orthostatic tachycardia syndrome); presence of intravascular lymphocytes on biopsy of abdominal, thigh, and buttock skin (intravascular B cell lymphoma); and a higher than normal density of mast cells in the absence of other inflammatory cell types (mast cell activation syndrome). The skin is clearly a critical window for understanding extracutaneous disease, a concept well exemplified by the myriad of diseases suggested by the microscopic and/or ultrastructural examination of clinically normal skin and therefore establishing the normal skin biopsy as an important tool for understanding certain extracutaneous reactive, neoplastic and paraneoplastic syndromes as well as small fiber neuropathy.

Eculizumab as Salvage Treatment for Thrombotic Microangiopathy After Lung Transplantation.

Thrombotic microangiopathy (TMA) is a rare complication after lung transplantation (LT) that has seldom been characterized in detail. Recent evidence has linked TMA other than primary atypical hemolytic uremic syndrome (aHUS) with hyperactivation of the complement alternative pathway. The focus of this investigation was to analyze the treatment response with eculizumab in TMA after LT. Case series where we have studied 11 patients with TMA after LT from 2 Spanish tertiary healthcare centers. Clinical data and response rates to eculizumab are provided. The main indication for lung transplant was chronic obstructive pulmonary disease (COPD) (36%) and most cases (82%) received bilateral LT. The median time to TMA diagnosis was 11.6 months (4.7-28.9) and the TMA trigger in the majority of cases (73%) was immunosuppressive drugs. Platelet and hemoglobin nadir were 58×103/µL (24-108) and 7.7g/dL (7.1-7.9), respectively. All cases presented acute kidney injury (AKI) with a median creatinine of 4mg/dL (3.2-4.8) and 54.5% required acute dialysis. Eculizumab was started after a median time of 8 days (6-14) with a median duration of 3 weeks (2-8). Complete TMA response was observed in 7 (63.6%) cases and hematologic response in 10 (90.9%). The time to hematologic and renal response was 23 days (13-29) and 28 days (14-46), respectively. TMA after LT is infrequent but potentially devastating. Our findings suggest that short cycles of eculizumab may be effective for severe TMA after LT.

Complex presentation of atypical hemolytic uremic syndrome: A case study

This case study discusses atypical hemolytic uremic syndrome (aHUS) in a 67-year-old female who presented with hypertension and hyperlipidemia 8 days after a suspected foodborne illness. Her initial presentation included acute respiratory and renal failure in which her condition required extensive re-warming, intubation, pressor or vasopressor therapy, continuous renal replacement therapy or hemodialysis, broad-spectrum antibiotic therapy, and blood and culture workups. Kidney function also showed signs of renal failure, metabolic acidosis, thrombocytopenia, and an elevated level of lactate dehydrogenase in the laboratory results. Radiological investigations demonstrated enteritis, colitis, and an ischemic infarct without hemorrhage. Multidisciplinary consultations achieved the importance and urgency of early diagnosis and treatment of aHUS to prevent irreversible organ damage. This case highlights the role of a timely diagnosis and interprofessional patient care in the treatment of severe aHUS.

Long-Term Outcomes of Anticomplement Factor H Antibody Positive Versus Negative Atypical Hemolytic Uremic Syndrome

Background Atypical hemolytic uremic syndrome (aHUS) is a severe thrombotic microangiopathy predominantly affecting the kidneys, often associated with complement dysregulation. This study is aimed to analyze the clinical characteristics, treatment outcomes, and long-term implications of aHUS in a resource-limited setting. Materials and Methods A retrospective observational study conducted at an institute between January 2016 and December 2022 included all patients with aHUS, excluding secondary causes and renal transplant recipients. Demographic profiles, clinical features, laboratory parameters, treatment modalities (immunosuppression and plasma exchange), and outcomes were collected. Anticomplement Factor H (anti-CFH) antibody, complement levels, and genetic mutation analysis were performed to ascertain etiological factors. The patient and renal outcomes of anti-CFH positive and negative patients on long-term follow-up were compared. Results Fifty-seven patients (mean age: 12.5 ± 4.9 years; 63% males) were analyzed. Among them, 33 (57.9%) tested positive for anti-CFH antibodies and eight presented postpartum. Initial remission was achieved in 42 (73.6%) patients, with 13 (22.8%) partial and 29 (50.9%) complete remission. The median follow-up duration was 24 months [interquartile range (IQR) 8.5–84]; 12 (21%) patients died, with two deaths during the index admission, six among nonresponders, and 4 among responders. Dialysis-free renal survival was superior in anti-CFH seropositive patients (81.2%) compared to seronegative counterparts (55.9%), while patient survival was statistically similar between the two groups. Elevated anti-CFH titers (>4000 AU/ml), age ≥16 years, female gender, and seizures predicted nonresponsiveness. Conclusion Anti-CFH antibody associated aHUS had better kidney outcomes than the seronegative counterparts. In resource limited settings, a combination of plasma exchange and immunosuppression showed promising results in the short and long term.

Postpartum Renal Cortical Necrosis: A Case Series

Rationale & ObjectivePostpartum renal cortical necrosis (postpartum RCN) is a severe form of obstetric acute kidney injury. This study aimed to identify clinicopathological features in Chinese postpartum RCN cases to determine how pathologic findings may contribute to the treatment and prognosis. Study DesignSingle-center, case series Setting & ParticipantsTwelve patients with postpartum RCN had kidney biopsies at Peking University First Hospital between 2014 and 2021. The diagnosis of postpartum RCN was made according to typical MRI or pathological features. Clinical, laboratory and pathological data were compared between patients with eGFR <30 (poor outcome) and ≥30 ml/min/1.73 m2 after six months. ObservationsAll postpartum RCN patients presented with stage 3 AKI attributed to a probable atypical hemolytic uremic syndrome. Pregnancy terminations occurred at a median gestational age of 35.5 weeks. Kidney biopsy was performed ranging 18 days to 4 months from delivery. Upon biopsy, hemoglobin, platelet count and LDH levels had been restored to 137 g/L, 214 ×109/L and 231.50±65.01 U/L, respectively. Four patients exhibited poor outcome, demonstrating higher schistocyte count, serum creatinine and mean arterial pressure at onset. Pathologically, glomerular segmental sclerosis was prevalent. The NOS variant was the most common type, followed by collapsing variant, cellular variant, and tip variant. Patients with poor kidney outcome had more glomerular coagulative necrosis, capillary thrombosis, extensive cortical coagulative necrosis, and pronounced arteriole/artery lesions including increased interlobular arteriole intimal edema and fibrin thrombosis, but a lower occurrence of segmental sclerosis. LimitationsLimited sample size and retrospective design. ConclusionsOur research has identified key pathological features in postpartum RCN patients with aHUS, highlighting the necessity for more effective therapeutic options. There is a clear demand for non-invasive biomarkers that can accurately track disease progression and inform treatment duration for long-term outcomes improvement.

Recent data on atypical hemolytic uremic syndrome associated with pregnancy, kidney transplantation or hypertensive emergency

Les microangiopathies thrombotiques (MAT) sont un groupe hétérogène de pathologies caractérisées à différents degrés par une anémie hémolytique mécanique, une thrombopénie et une occlusion microvasculaire histologique. Les MAT peuvent se compliquer de multiples atteintes d’organe, principalement neurologiques et néphrologiques (définissant alors le syndrome hémolytique et urémique). La classification fondée sur la physiopathologie de la maladie a mis en évidence l’importance de la dérégulation de la voie alterne du complément dans les SHU atypiques (SHUa) (non-liés aux infections). Cependant, la physiopathologie et le traitement de nombreuses formes de SHUa dans des contextes spécifiques (tels que la grossesse, la transplantation rénale ou l’urgence hypertensive) restent mal caractérisés. Dans cet article, nous reprenons les avancées diagnostiques et thérapeutiques récentes dans ces trois formes de SHUa aux contextes spécifiques. Nous montrons les spécificités de ces formes et décrivons les enjeux actuels et futurs de leur prise en charge.

Генетически-фенотипический профиль детей с атипичным гемолитико-уремическим синдромом

Atypical hemolytic uremic syndrome (aHUS) is a life-threatening disease caused by dysregulation of the alternative complement pathway as a result of mutations in complement genes or the formation of antibodies (AB) to some of the complement factors. Identification of the gene mutations incidence and the corresponding phenotypic features in pediatric patients with aHUS in Russia is aimed at improving the diagnosis and prognosis of the disease as well as treatment tactics planning for patient management. The purpose of this research was to determine the patterns of progression, prognosis and outcomes of aHUS in children depending on their genetic profile. Materials and methods used: the Article represents data from a retro- and prospective analyses of the characteristics of the course of aHUS in 172 children depending on their genetic profile performed in Jan. 2012-Feb. 2022. The sporadic form of aHUS was diagnosed after exclusion of the other forms of thrombotic microangiopathy (TMA), the familial form (in cases with the familial records), the acquired (CFH-Ab HUS) in cases with AB increase to factor H. AutoAb against factor H was determined by enzyme-linked immunosorbent assay (ELISA-VIDITEST anti-complement factor H). The search for mutations (n=167) was carried out using Next-generation Sequencing (NGS) and Sanger sequencing methods. Results: the sporadic form of aHUS was diagnosed in 96.9% of cases, familial in 3.1% and CFH-Ab HUS in 23.8%. The genetic nature of aHUS was confirmed in 53.4% of cases. Pathogenic mutations were detected in 8.6% of cases, probably pathogenic in 42.8% and those with unclear clinical significance in 46.8%. The complement genes mutations were detected in 88.5% of cases and mutations of genes not related to the complement system (ADAMTS13, DGKE, INF2) in 11.5%. The most frequently identified mutations were in the CFH (17.1%), C3 (12.9%) and CD46 (12.9%) genes and less frequently in CFI (7.1%), THBD (5.7%), CFHR5 (5.7%) and CFB (1.4%). In children with CFH-Ab HUS, the CFHR1/CFHR3 deletion was detected in 87.8% of cases, including in 19.4% in combination with mutations of unknown clinical significance. Multiple organ failure syndrome had developed in 77.8% of cases in children with pathogenic/probably pathogenic mutations, in 85.3% in patients with mutations of unknown clinical significance, in 91.8% in patients without mutations and in 83.3% in patients with CFHR1/CFHR3 deletion. Chronic kidney disease (CKD) stages 3 to 5 in sporadic/familial aHUS, regardless of genetic profile, had counted for 14.5% and 16.7% in CFH-Ab HUS. Lethal outcome occurred in 4.3% of cases in the presence of mutations, in 4.9% in the absence of mutations and in 2.8% in cases of CFHR1/CFHR3 deletion. Relapses of aHUS prior to the Eculizumab treatment had developed more often in the presence of CFHR1/CFHR3 mutations and deletion in comparison with children without mutations (31.4% v. 13.1%, p=0.0313 and 44.4% v. 13.1%, p= 0.004). Relapse of aHUS after discontinuation of the Eculizumab therapy had developed in 16.4% of cases. Risk factors for the relapse of aHUS were as follows: patient’s age above 12 months old at the time of the development of aHUS, severe arterial hypertension in the acute period, the use of Eculizumab at the fourth week after the onset of the disease and/or later, recurrent course of aHUS and the presence of CKD prior to the start of the Eculizumab therapy. Conclusion: The genetic profile of patients does not determine the severity and outcome of aHUS though it does affect the relapse rate. The prognosis and survival of patients with aHUS are determined by the severity of the acute period and the timeliness of the complement blocking therapy management.

Systematic Review of Individual Patient Data COVID-19 Infection and Vaccination–Associated Thrombotic Microangiopathy

Sporadic cases of atypical hemolytic uremic syndrome (aHUS) have been described in the literature in association with COVID-19 infection and vaccination in adults and pediatric patients. The exact mechanisms underlying COVID-19-associated thrombotic microangiopathies (TMAs) remain incompletely understood. Herein, we present a detailed meta-analysis of the clinical characteristics, outcomes, and management strategies of COVID-19-associated aHUS and thrombotic thrombocytopenic purpura (TTP). This study was performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses updated guidelines. PubMed was utilized for searching for case reports and series. Adverse outcome at last follow-up was defined as estimated glomerular filtration rate< 30 ml/min per 1.73 m2 (patients with aHUS), no remission with therapy, or patient death. Data were analyzed using Wilcoxon rank and Chi-square tests. Our analysis cohort included 118 studies reporting on 170 patients. These included 84 cases of aHUS and 86 cases of TTP resulting from COVID-19 infection (n= 92) or vaccination (n= 78). Significantly more cases of aHUS were reported after infection (n= 65) than immunization (n= 19), compared to TTP, where the reverse was true (n= 27 and n= 59, respectively; P< 0.001). In patients with aHUS with stage 3 acute kidney injury (AKI), requirement of kidney replacement therapy (KRT) was seen in three-fourths of the cohort for a median of 15. In patients with TTP, severe COVID-19 infection (P= 0.04) predicted nonremission or death at last follow-up. Administration of i.v., rituximab and caplacizumab were protective (P= 0.03 and P= 0.06, respectively). Immune TTP (iTTP) was reported more often than HUS following mRNA vaccines (81% vs. 58%; P= 0.06). COVID-19 infection and vaccination are a potential trigger for onset or relapse of aHUS and TTP, especially in patients who are not on maintenance complement inhibitors or immunosuppression.

Annual trends in atypical haemolytic uremic syndrome management in Japan and factors influencing early diagnosis and treatment: a retrospective study

Atypical haemolytic uremic syndrome (aHUS) is a rare disorder characterised by complement-mediated thrombotic microangiopathy (TMA). Despite clinical guidelines, the diagnosis and treatment of aHUS in its early stages remains challenging. This study examined the annual trends in aHUS clinical practices in Japan and explored factors influencing early diagnosis and treatment. Using data from the 2011–2020 Diagnosis Procedure Combination database, 3096 cases with the HUS disease code were identified, of which 217 were confirmed as aHUS and treated with eculizumab or plasma exchange. Early initiation, defined as starting eculizumab or plasma exchange within 7 days of admission, was the focus of the study. Our study revealed no significant changes over time in the number of aHUS diagnoses, cases treated with eculizumab, or early initiation cases. Early initiation cases underwent haemodialysis earlier and had ADAMTS13 activity measured earlier, shorter hospital stays, and lower hospitalisation costs than late initiation cases. In conclusion, we found no increase in the number of newly diagnosed aHUS cases or early treatment initiation over time. Early recognition of TMA and differentiation of the causative disease are crucial for identifying potential aHUS cases, which may lead to better patient prognoses.

Protein-losing enteropathy as a new phenotype in atypical hemolytic uremic syndrome caused by CD46 gene mutation.

Atypical hemolytic uremic syndrome (aHUS) is a life-threatening thrombotic microangiopathy. Genetic defects in the alternative complement (AP) pathway have been identified in 60-70% of individuals. Eculizumab is recommended as a first-line therapy. We collected the clinical data of a pediatric patient with aHUS accompanied by protein-losing enteropathy (PLE). Genetic testing was performed. Related literature on aHUS combined with PLE was reviewed. A 15-year-old Chinese girl was diagnosed with aHUS at 3.7years of age and experienced five episodes; her symptoms completely resolved with plasma treatment. Severe gastrointestinal symptoms and hypoalbuminemia presented after the first episode, and PLE was diagnosed. A novel homozygous CD46 variant was identified, and FACS revealed significantly decreased CD46 expression. She presented at a recent relapse with persistent GI symptoms and headache and progressed to chronic kidney failure; peritoneal dialysis was initiated. Eculizumab was given 8months after the last recurrence. Surprisingly, PLE was cured. Afterward, dialysis was discontinued, and eGFR recovered to 44.8ml/min/1.73 m2. A review of the literature indicated that PLE with thrombosis was caused by CD55 variants via hyperactivation of the AP system. We report an aHUS patient with PLE caused by CD46 variants. Symptoms of both PLE and aHUS were significantly alleviated in our patient and patients with CD55 variants treated with eculizumab, indicating that PLE was a new symptom of aHUS in our patient with a CD46 variant. Our case expands the phenotype of aHUS caused by a CD46 mutation and provides evidence of the efficacy of eculizumab after a long phase of chronic kidney failure.

Bronchopleural fistula management in a pediatric patient requiring extracorporeal membrane oxygenation.

Bronchopleural fistula (BPF) is a connection between the bronchus and pleural cavity. It is associated with high morbidity and mortality and management of BPF has not been well described in the pediatric population. We describe a 2-year-old girl who presented with fever and increased work of breathing, found to have atypical hemolytic uremic syndrome and Streptococcus necrotizing pneumonia with development of persistent air leak due to bronchopleural fistulas requiring extracorporeal membrane oxygenation (ECMO). Three endobronchial valves were placed with successful resolution of bronchopleural fistulas. She required tracheostomy for chronic respiratory failure and endobronchial valves were eventually removed. Approximately 3.5 months after discharge to acute care rehabilitation, tracheostomy was successfully decannulated. This case highlights the successful use of endobronchial valves for resolution of BPF while on ECMO as well as the importance of further studies on optimal candidates, timing and duration of intervention in addition to sequelae of endobronchial valve placement.

The potential for therapeutic drug monitoring of belatacept and other biologicals in solid organ transplantation.

In solid organ transplantation (SOT), biologicals such as recombinant therapeutic proteins, monoclonal antibodies, fusion proteins and conjugates are increasingly used for immunosuppression, desensitization, ABO (blood group) incompatibility, antibody-mediated rejections and atypical haemolytic uremic syndrome. In this paper, we review the medical evidence available for biologicals used in SOT and the potential for improvement by the application of therapeutic drug monitoring (TDM) and model-informed precision dosing. Biologicals are used for off-label indications within the field of SOT, building on the experience from their use on labelled indications. Dosing is currently mostly standard, and experience vs. effect and toxicity is limited. Pharmacokinetic characteristics of these large, partly also immunogenic molecules differ from those of traditional small molecules. Individualization by concentration measurements and modelling has mostly been proof-of-concept or feasibility studies that lack the power to provide evidence for improvement in clinical outcome. For some drugs such as alemtuzumab, eculizumab, rituximab, tocilizumab and belatacept, studies have demonstrated significant interindividual variability in pharmacokinetics. Variability in absorption from subcutaneous administration may increase interindividual variability. There is also an economic aspect of appropriate dosing that needs to be pursued. Available assays and models to refine interpretation are in place, but trials of adequate size to document the usefulness of TDM and MIPD are scarce. Collaboration within the TDM community seems mandatory to establish studies of sufficient strength to provide evidence for the use of biologicals that are currently used off-label in SOT and furthermore to identify the settings where TDM may be beneficial.

Kidney Transplantation in Patients With aHUS: A Comparison of Eculizumab Prophylaxis Versus Rescue Therapy.

Guidelines advise eculizumab prophylaxis for most kidney transplant recipients with atypical hemolytic uremic syndrome (aHUS). However, recurrence rates may be overestimated, and starting eculizumab at relapse ("rescue therapy") may prevent graft loss. Randomized controlled trials have not compared the efficacy, safety, and costs of different treatment strategies. We performed a comparative study, including a previously described Dutch cohort treated with rescue therapy and a UK cohort using eculizumab prophylaxis. In the Netherlands, we selected all adult patients with aHUS who received a kidney transplant between 2010 and 2021 in the Radboud University Medical Center (n = 30) and enriched this cohort with 8 patients who received rescue therapy in other centers. The UK cohort included all adult patients with aHUS at moderate or high risk of recurrence, transplanted between 2013 and 2017 with prophylactic eculizumab. We included 38 Dutch patients and 35 UK patients. Characteristics were comparable, although the UK cohort included more patients with a complement factor H SCR20 mutation or hybrid gene (31% versus 5%; P < 0.01), and more Dutch patients received living donor kidneys (66% versus 20%; P < 0.001). Follow-up was comparable (the Dutch patients 70.8 mo, range, 10-134; UK patients 55.4 mo, range, 2-95). Eighteen (47%) Dutch patients received rescue therapy. Death-censored graft survival was not significantly different (the Dutch patients 1 y, 3 y, and 6 y: 97.4%, 91.2%, and 87.1%, respectively; UK patients 1 y, 3 y, and 6 y: 97.1%, 88.2%, and 65.6%, respectively, log-rank P = 0.189). In a population characterized by low prevalence of "very high risk" genes, who were predominantly transplanted using an endothelial protective regime, death-censored graft survival with eculizumab rescue therapy was not inferior to prophylaxis.

Anti-C5 monoclonal antibody treatment showing pathological resolution of complement-mediated atypical hemolytic uremic syndrome: a case report

BackgroundNo reports have shown histological changes before and after anti-C5 monoclonal antibody treatment in patients with atypical hemolytic uremic syndrome (aHUS). Here, we report a rare case of complement-mediated aHUS with a complement factor H (CFH) mutation and anti-CFH antibodies who underwent multiple kidney biopsies.Case presentationA 53-year-old woman developed aHUS with CFH gene mutation [c.3572C > T (p. Ser1191 Leu)] and anti-CFH antibodies. Her father had succumbed to acute kidney injury (AKI) in his 30 s. She exhibited AKI, thrombocytopenia, and hemolytic anemia with schistocytes. After improving the platelet count with one session of plasma exchange, a kidney biopsy was performed one month after the onset of symptoms. Blood vessel thrombosis, obvious endothelial swelling, endocapillary hypercellularity, and subendothelial exudative lesions in the glomeruli and arterioles were detected. Anti-C5 monoclonal antibody treatment with eculizumab immediately improved disease activity. A second biopsy 3 months later revealed marked improvement of endothelial injuries with residual membrane double contours and exudative lesions. A third biopsy at 17 months after gradual improvement of kidney function showed a further decrease of double contours along with alterations of the exudative lesions to fibrous intimal thickening.ConclusionsThis is the first report showing the pathophysiology of aHUS in the kidneys and the efficacy of anti-C5 monoclonal antibody treatment by presenting serial kidney pathological features before and after anti-C5 monoclonal antibody treatment. Since her CFH mutation was considered the most important pathological condition, treatment centered on eculizumab was administered, resulting in a good long-term prognosis. In addition, kidney pathological resolution in aHUS occurred over 1 year after anti-C5 monoclonal antibody treatment.