Haemolytic uraemic syndrome

Delving into human α1,4-galactosyltransferase acceptor specificity: The role of enzyme dimerization

Human α1,4-galactosyltransferase (A4galt), a Golgi apparatus-resident GT, synthesizes Gb3 glycosphingolipid (GSL) and P1 glycotope on glycoproteins (GPs), which are receptors for Shiga toxin types 1 and 2. Despite the significant role of A4galt in glycosylation processes, the molecular mechanisms underlying its varied acceptor specificities remain poorly understood. Here, we attempted to elucidate A4galt specificity towards GSLs and GPs by exploring its interaction with GTs with various acceptor specificities, GP-specific β1,4-galactosyltransferase 1 (B4galt1) and GSL-specific β1,4-galactosyltransferase isoenzymes 5 and 6 (B4galt5 and B4galt6). Using a novel NanoBiT assay, we found that A4galt can form homodimers and heterodimers with B4galt1 and B4galt5 in two cell lines, human embryonic kidney cells (HEK293T) and Chinese hamster ovary cells (CHO-Lec2). We found that A4galt-B4galts heterodimers preferred N-terminally tagged interactions, while in A4galt homodimers, the favored localization of the fused tag depended on the cell line used. Furthermore, by employing AlphaFold for state-of-the-art structural prediction, we analyzed the interactions and structures of these enzyme complexes. Our analysis highlighted that the A4galt-B4galt5 heterodimer exhibited the highest prediction confidence, indicating a significant role of A4galt heterodimerization in determining enzyme specificity toward GSLs and GPs. These findings enhance our knowledge of A4galt acceptor specificity and may contribute to a better comprehension of pathomechanisms of the Shiga toxin-related diseases.

Complement-targeted therapeutics: Are we there yet, or just getting started?

Therapeutic interventions in the complement system, a key immune-inflammatory mediator and contributor to a broad range of clinical conditions, have long been considered important yet challenging or even unfeasible to achieve. Almost 20 years ago, a spark was lit demonstrating the clinical and commercial viability of complement-targeted therapies. Since then, the field has experienced an impressive expansion of targeted indications and available treatment modalities. Currently, a dozen distinct complement-specific therapeutics covering several intervention points are available in the clinic, benefiting patients suffering from eight disorders, not counting numerous clinical trials and off-label uses. Observing this rapid rise of complement-targeted therapy from obscurity to mainstream with amazement, one might ask whether the peak of this development has now been reached or whether the field will continue marching on to new heights. This review looks at the milestones of complement drug discovery and development achieved so far, surveys the currently approved drug entities and indications, and ventures a glimpse into the future advancements yet to come.

The immune regulatory role of lymphangiogenesis in kidney disease

The renal lymphatic system is critical for maintaining kidney homeostasis and regulating the immune response inside the kidney. In various kidney pathological situations, the renal lymphatic network experiences lymphangiogenesis, which is defined as the creation of new lymphatic vessels. Kidney lymphangiogenesis controls immunological response inside the kidney by controlling lymphatic flow, immune cell trafficking, and immune cell regulation. Ongoing study reveals lymphangiogenesis's different architecture and functions in numerous tissues and organs. New research suggests that lymphangiogenesis in kidney disorders may regulate the renal immune response in various ways. The flexibility of lymphatic endothelial cells (LECs) improves the kidney's immunological regulatory function of lymphangiogenesis. Furthermore, current research has shown disparate findings regarding its impact on distinct renal diseases, resulting in contradictory outcomes even within the same kidney condition. The fundamental causes of the various effects of lymphangiogenesis on renal disorders remain unknown. In this thorough review, we explore the dual impacts of renal lymphangiogenesis on several kidney pathologies, with a particular emphasis on existing empirical data and new developments in understanding its immunological regulatory function in kidney disease. An improved understanding of the immunological regulatory function of lymphangiogenesis in kidney diseases might help design novel medicines targeting lymphatics to treat kidney pathologies.

Open-label, controlled, phase 2 clinical trial assessing the safety, efficacy, and pharmacokinetics of INM004 in pediatric patients with Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome

BACKGROUND

Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) is a severe condition mainly affecting children. It is one of the leading causes of acute kidney injury in the pediatric population. There is no established therapy for this disease. INM004 is an anti-Shiga toxin composed of equine polyclonal antibodies. This study is aimed at assessing the safety, pharmacokinetics, and efficacy of INM004 in pediatric patients with STEC-HUS.

METHODS

Phase 2, open-label clinical trial with an historical control arm. Patients in the treatment arm received two doses of INM004. The primary endpoints were the safety profile, pharmacokinetics, and efficacy (dialysis days) of INM004. Secondary endpoints included other kidney and extrarenal outcomes. Propensity score matching was used for efficacy comparisons between arms.

RESULTS

Fifty-seven and 125 patients were enrolled in the treatment and control arm, respectively. After propensity score matching, 52 patients remained in each arm. INM004 was well-tolerated. Eight adverse events were considered possibly related, none of which were serious or severe. In the primary efficacy endpoint, patients of the treatment arm presented a non-statistically significant difference of two dialysis days. On secondary endpoints, non-statistically significant trends toward fewer patients needing dialysis and dialysis for more than 10 days, and shorter time to glomerular filtration rate normalization, were observed favoring the treatment arm.

CONCLUSIONS

INM004 showed an adequate safety profile. Efficacy non-statistically significant trends suggesting a beneficial effect in the amelioration of kidney injury were observed. These results encourage the conduction of a phase 3 study of INM004 in pediatric patients with STEC-HUS.

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

Introduction

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).

Methods

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.

Results

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).

Conclusion

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.

Correlation between a 2-week change in platelet count and clinical outcomes after the initiation of ravulizumab treatment in adult patients with atypical hemolytic uremic syndrome: post-hoc analysis of the phase III trial

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a rare disease with poor outcomes when untreated, in which ravulizumab or eculizumab are the standard of care where available. It has been proposed to regularly monitor platelet counts as an early response to ravulizumab or eculizumab. This study aimed to investigate the association between the early response to ravulizumab treatment and renal outcomes through 26 weeks in complement inhibitor-naïve adults with aHUS.

METHODS

Adult patients with aHUS enrolled in the ALXN1210-aHUS-311 phase III study of ravulizumab were divided into two groups according to the achievement of complete thrombotic microangiopathy (TMA) response, i.e., platelet count and lactate dehydrogenase (LDH) normalization and ≥ 25% improvement in serum creatinine (sCr) from baseline, by 26 weeks and baseline characteristics were compared. Changes in hematologic parameters, platelet count and LDH, were compared between the two groups. Finally, we examined whether early hematologic improvement was associated with renal recovery (dialysis discontinuation or ≥ 25% improvement in sCr from baseline) through 26 weeks.

RESULTS

Of 56 ravulizumab-treated patients, 30 achieved complete TMA response for 26 weeks, and 26 did not. Patients with complete TMA response showed rapid improvements in platelet counts. In patients without complete TMA response, delayed normalization of platelet counts was observed. By day 15, 93.3% (28/30) of patients with complete TMA response at 26 weeks and 26.9% (7/26) of patients without complete TMA response achieved platelet normalization. At 26 weeks, 62.5% (35/56) achieved renal recovery; however, 37.5% (21/56) did not. In patients with renal recovery, 85.7% (30/35) of patients had platelet count normalization by day 15; in patients without renal recovery, 23.8% (5/21) of patients had platelet count normalization (P < 0.0001). Receiver operator characteristic curve analysis showed a moderate association between platelet counts on day 8/15 and renal recovery within 26 weeks (day 8: area under the curve [AUC] = 0.7985; day 15: AUC = 0.8406).

CONCLUSIONS

Platelet count normalization occurred in 62.5% (35/56) by day 15 after ravulizumab initiation and was associated with renal recovery through 26 weeks in complement inhibitor-naïve adults with aHUS.

TRIAL REGISTRATION

This study was performed as a post-hoc analysis of the ALXN1210-aHUS-311 phase III clinical trial (NCT02949128, registered October 25, 2016).

Postpartum Renal Cortical Necrosis: A Case Series

Rationale & Objective

Postpartum renal cortical necrosis (postpartum RCN) is a severe form of obstetric acute kidney injury. This study aimed to identify clinicopathologic features in Chinese postpartum RCN cases to determine how pathologic findings may contribute to the treatment and prognosis.

Study Design

Single-center, case series.

Setting & Participants

Twelve 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 magnetic resonance imaging or pathologic features. Clinical, laboratory, and pathologic data were compared between patients with estimated glomerular filtration rate <30 (poor outcome) and ≥30 mL/min/1.73 m2 after 6 months.

Observations

All patients with postpartum RCN presented with stage 3 acute kidney injury attributed to a probable atypical hemolytic uremic syndrome. Pregnancy terminations occurred at a median gestational age of 35.5 weeks. Kidney biopsy was performed from 18 days to 4 months from delivery. On biopsy, hemoglobin, platelet count, and lactate dehydrogenase 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 "not otherwise specified" 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.

Limitations

Limited sample size and retrospective design.

Conclusions

We identified key pathologic features in patients with postpartum RCN and atypical hemolytic uremic syndrome, highlighting the necessity for more effective therapeutic options. There is a clear demand for noninvasive biomarkers that can accurately track disease progression and inform treatment duration for long-term outcomes improvement.

Non-plasmapheresis Approaches for Managing Severe Renal Thrombotic Microangiopathy: A Report of 7 Cases

C5-blockers are the established treatment for complement-mediated hemolytic uremic syndrome (CM-HUS). However, CM-HUS, lacking a definitive test, prompts plasma exchanges as a common first-line therapy, pending further assessments, despite complications and limited evidence in this indication. Recent experts' opinion endorses C5-blockers as the initial treatment for severe renal thrombotic microangiopathy (TMA). This retrospective, single-center study reports a series of 7 patients treated with a plasmapheresis-free approach. All patients presented with severe renal TMA symptoms and low French score and received prompt 900mg eculizumab within a median of 9 hours from admission. Hematological recovery was rapid, and renal function improved in 6 patients within 6.5 days, with a median hospital stay of 16 days. No rescue plasmapheresis was used. We report 7 cases of an early C5-blocker and plasmapheresis-free strategy in severe renal TMA suspicious for CM-HUS, demonstrating promising initial results. Clinical trials are needed to confirm the efficacy and safety of this approach. Addressing the high cost of C5-blocking therapies and exploring cost-effective alternatives is also crucial for broader implementation and accessibility in targeted therapies for adult renal TMA.

Outcome 10 years after Shiga toxin-producing E. coli (STEC)-associated hemolytic uremic syndrome: importance of long-term follow-up

BACKGROUND

Hemolytic uremic syndrome (HUS) is an important cause of acute kidney injury in children. HUS is known as an acute disease followed by complete recovery, but patients may present with kidney abnormalities after long periods of time. This study evaluates the long-term outcome of Shiga toxin-producing Escherichia coli-associated HUS (STEC-HUS) in pediatric patients, 10 years after the acute phase of disease to identify risk factors for long-term sequelae.

METHODS

Over a 6-year period, 619 patients under 18 years of age with HUS (490 STEC-positive, 79%) were registered in Austria and Germany. Long-term follow-up data of 138 STEC-HUS-patients were available after 10 years for analysis.

RESULTS

A total of 66% (n = 91, 95% CI 0.57-0.73) of patients fully recovered showing no sequelae after 10 years. An additional 34% (n = 47, 95% CI 0.27-0.43) presented either with decreased glomerular filtration rate (24%), proteinuria (23%), hypertension (17%), or neurological symptoms (3%). Thirty had sequelae 1 year after STEC-HUS, and the rest presented abnormalities unprecedented at the 2-year (n = 2), 3-year (n = 3), 5-year (n = 3), or 10-year (n = 9) follow-up. A total of 17 patients (36.2%) without kidney abnormalities at the 1-year follow-up presented with either proteinuria, hypertension, or decreased eGFR in subsequent follow-up visits. Patients needing extracorporeal treatments during the acute phase were at higher risk of presenting symptoms after 10 years (p < 0.05).

CONCLUSIONS

Patients with STEC-HUS should undergo regular follow-up, for a minimum of 10 years following their index presentation, due to the risk of long-term sequelae of their disease. An initial critical illness, marked by need of kidney replacement therapy or plasma treatment may help predict poor long-term outcome.

Cancer-Associated Thrombotic Microangiopathy: Literature Review and Report of Five Cases

Thrombotic microangiopathy (TMA) is an anatomopathological lesion mediated by endothelial dysfunction and characterized by the creation of microthrombi in small vessels. In patients with cancer, it may be due to toxicity secondary to chemotherapy, tumor embolization, or hematopoietic progenitor transplantation. Cancer-associated TMA is an underestimated entity that generally appears in the final stages of the disease, although it may also be the initial manifestation of an underlying cancer. Support treatment is necessary in all cases and, depending on the cause, different targeted therapies may be used. The prognosis is very poor. In this article we present a comprehensive review of the existing literature on the physiological mechanisms of cancer-associated TMA. Afterwards, five clinical cases will be presented of patients who developed TMA and were diagnosed in our Department in 2023. We present a discussion of the different causes that triggered the condition, the possible reasons behind the underestimation of this pathology, and the measures that may be adopted.

Recurrent complement-mediated Hemolytic uremic syndrome after kidney transplantation

Hereditary forms of hemolytic uremic syndrome (HUS), formerly known as atypical HUS, typically involve mutations in genes encoding for components of the alternative pathway of complement, therefore they are often referred to as complement-mediated HUS (cHUS). This condition has a high risk of recurrence in the transplanted kidney, leading to accelerated graft loss. The availability of anti-complement component C5 antibody eculizumab has enabled successful transplantation with a notably reduced recurrence rate and improved prognosis. Open questions are related to the potential for complement inhibitor discontinuation, ideal timing of treatment withdrawal, and patient selection based on genetic abnormalities. Our review delves into the pathophysiology, classification, genetic predispositions, and management strategies for cHUS in the native and transplant kidneys.

Abbreviated protocol of plasma exchanges for patients with anti-factor H associated hemolytic uremic syndrome

BACKGROUND

Plasma exchanges (PEX) and immunosuppression are the cornerstone of management of anti-factor H (FH) antibody-associated atypical hemolytic uremic syndrome (aHUS), particularly if access to eculizumab is limited. The duration of therapy with PEX for anti-FH aHUS is empirical.

METHODS

We compared the efficacy of abbreviated PEX protocol (10-12 sessions) in a prospective cohort of patients diagnosed with anti-FH aHUS (2020-2022), to standard PEX protocol (20-22 sessions) in a historical cohort (2016-2019; n = 65). Efficacy was defined as 70% decline in anti-FH titers or fall to ≤ 1300 AU/ml at 4 weeks. Patients in both cohorts received similar immunosuppression with oral prednisolone, IV cyclophosphamide (5 doses) and mycophenolate mofetil. Outcomes included efficacy, rates of hematological remission and adverse kidney outcomes at 1, 3 and 6 months.

RESULTS

Of 23 patients, 8.2 ± 2.1 years old enrolled prospectively, two were excluded for significant protocol deviation. PEX was abbreviated in 18/21 (86%) patients to 11.5 ± 3.3 sessions. Abbreviation failed for lack of hematological remission by day 14 (n = 2) and persistent neurological manifestations (n = 1). All patients in whom PEX was abbreviated achieved > 70% reduction in anti-FH titers at day 28. The percentage fall in anti-FH titers was similar for the abbreviated vs. standard PEX protocols at 1, 3 and 6 months. At last follow-up, at median 50 months and 25 months for standard and abbreviated cohorts, the estimated GFR was similar at 104.8 ± 29.1 vs. 93.7 ± 53.4, respectively (P = 0.42).

CONCLUSION

Abbreviation of the duration of PEX is feasible and efficacious in reducing anti-FH titers. Short-term outcomes were comparable in patients managed by abbreviated and standard PEX protocols.

Anti-factor B antibodies in atypical hemolytic uremic syndrome

BACKGROUND

The etiology of atypical hemolytic uremic syndrome (aHUS) is unknown in 30-40% of patients. Anti-factor B (FB) antibodies are reported in C3 glomerulopathy (C3G) and immune-complex membranoproliferative glomerulonephritis (IC-MPGN), though not in aHUS.

METHODS

We screened patients < 18-year-old from cohorts of aHUS and C3G/idiopathic IC-MPGN. Anti-FB IgG antibodies were measured by ELISA and confirmed by Western blot. Normative levels were based on antibody levels in 103 healthy blood donors.

RESULTS

Prevalence of anti-FB antibodies was 9.7% (95% CI 6.1-14.5%; n = 21) in 216 patients with aHUS, including 11.5% (95% CI 6.4-18.5%; n = 14) in anti-FH associated aHUS and 11.8% (95% CI 4.4-23.9%; n = 6) in patients without a definitive genetic or autoimmune etiology. Patients with significant genetic variants did not show anti-FB antibodies. In patients with concomitant anti-FB and anti-FH antibodies, median anti-FH titers were higher (11,312 AU/mL vs. 4920 AU/mL; P = 0.04). Anti-FB antibody titer correlated with disease severity (hemoglobin and platelets; P < 0.05), declined following plasma exchange and increased during relapse. While 4/64 patients with C3G (6.3%) and 1/17 with IC-MPGN showed anti-FB antibodies, titers were higher in aHUS (544.8 AU/mL vs. 1028.8 AU/mL; P = 0.003).

CONCLUSION

Anti-FB antibodies are present in 6-10% of patients with aHUS and C3G/IC-MPGN, with higher titers in the former. The diagnostic and therapeutic implication of anti-FB antibodies in aHUS needs confirmation and further studies. The study shows propensity for autoantibody generation and co-existence of multiple risk factors for aHUS in Indian children.

Eculizumab in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome: a systematic review

BACKGROUND

Infection-associated hemolytic uremic syndrome (IA-HUS), most often due to infection with Shiga toxin-producing bacteria, mainly affects young children. It can be acutely life-threatening, as well as cause long-term kidney and neurological morbidity. Specific treatment with proven efficacy is lacking. Since activation of the alternative complement pathway occurs in HUS, the monoclonal C5 antibody eculizumab is often used off-label once complications, e.g., seizures, occur. Eculizumab is prohibitively expensive and carries risk of infection. Its utility in IA-HUS has not been systematically studied. This systematic review aims to present, summarize, and evaluate all currently available data regarding the effect of eculizumab administration on medium- to long-term outcomes (i.e., outcomes after the acute phase, with a permanent character) in IA-HUS.

METHODS

PubMed, Embase, and Web of Science were systematically searched for studies reporting the impact of eculizumab on medium- to long-term outcomes in IA-HUS. The final search occurred on March 2, 2022. Studies providing original data regarding medium- to long-term outcomes in at least 5 patients with IA-HUS, treated with at least one dose of eculizumab during the acute illness, were included. No other restrictions were imposed regarding patient population. Studies were excluded if data overlapped substantially with other studies, or if outcomes of IA-HUS patients were not reported separately. Study quality was assessed using the ROBINS-I tool for risk of bias in non-randomized studies of interventions. Data were analyzed descriptively.

RESULTS

A total of 2944 studies were identified. Of these, 14 studies including 386 eculizumab-treated patients met inclusion criteria. All studies were observational. Shiga toxin-producing E. coli (STEC) was identified as the infectious agent in 381 of 386 patients (98.7%), effectively limiting the interpretation of the data to STEC-HUS patients. Pooling of data across studies was not possible. No study reported a statistically significant positive effect of eculizumab on any medium- to long-term outcome. Most studies were, however, subject to critical risk of bias due to confounding, as more severely ill patients received eculizumab. Three studies attempted to control for confounding through patient matching, although residual bias persisted due to matching limitations.

DISCUSSION

Current observational evidence does not permit any conclusion regarding the impact of eculizumab in IA-HUS given critical risk of bias. Results of randomized clinical trials are eagerly awaited, as new therapeutic strategies are urgently needed to prevent long-term morbidity in these severely ill patients.

SYSTEMATIC REVIEW REGISTRATION NUMBER

OSF Registries, MSZY4, Registration DOI https://doi.org/10.17605/OSF.IO/MSZY4 .

A Successful Approach to Diagnosing Shiga-like Toxin-Producing Escherichia coli-Induced Colitis

Shiga-like toxin-producing Escherichia coli (STEC) is a well-known cause of foodborne acute diarrheic diseases, especially in children and the elderly. The potentially fatal complications associated with toxin production range from bloody diarrhea and ischemic colitis to kidney failure, hemolytic-uremic syndrome (HUS), and colon perforation. Here, we describe a case and literature review of STEC-induced colitis, highlighting the clinical features and the necessary tools for the best diagnostic approach and management. Facing challenging differential diagnosis, ranging from ischemic colitis and inflammatory bowel disease to infectious processes due to a pathogenic or opportunistic agent, we conducted a step-by-step exploration. Following bacteriological investigation, imagistic screening, and colonoscopy, we ruled out some of the initial suppositions and reached a final diagnosis, while also considering the pathological results. Although antibiotics are not indicated in this pathology, our patient did receive antibiotics, given the risk of translocation and colon perforation, without any associated complications such as HUS or peritonitis. Detailed and rigorous investigations conducted by a multi-specialty team are required for prompt medical support. Coping with the symptoms and refraining from further complications are the mainstem aims of treatment.

Thrombotic microangiopathy after kidney transplantation: Expanding etiologic and pathogenetic spectra

Thrombotic microangiopathy (TMA) is an uncommon but serious complication that not only affects native kidneys but also transplanted kidneys. This review is specifically focused on post-transplant TMA (PT-TMA) involving kidney transplant recipients. Its reported prevalence in the latter population varies from 0.8% to 14% with adverse impacts on both graft and patient survival. It has many causes and associations, and the list of etiologic agents and associations is growing constantly. The pathogenesis is equally varied and a variety of patho genetic pathways lead to the development of microvascular injury as the final common pathway. PT-TMA is categorized in many ways in order to facilitate its management. Ironically, more than one causes are contributory in PT-TMA and it is often difficult to pinpoint one particular cause in an individual case. Pathologically, the hallmark lesions are endothelial cell injury and intravascular thrombi affecting the microvasculature. Early diagnosis and classification of PT-TMA are imperative for optimal outcomes but are challenging for both clinicians and pathologists. The Banff classification has addressed this issue and has developed minimum diagnostic criteria for pathologic diagnosis of PT-TMA in the first phase. Management of the condition is also challenging and still largely empirical. It varies from simple maneuvers, such as plasmapheresis, drug withdrawal or modification, or dose reduction, to lifelong complement blockade, which is very expensive. A thorough understanding of the condition is imperative for an early diagnosis and quick treatment when the treatment is potentially effective. This review aims to increase the awareness of relevant stakeholders regarding this important, potentially treatable but under-recognized cause of kidney allograft dysfunction.

Pregnancy as a susceptible state for thrombotic microangiopathies

Pregnancy and the postpartum period represent phases of heightened vulnerability to thrombotic microangiopathies (TMAs), as evidenced by distinct patterns of pregnancy-specific TMAs (e.g., preeclampsia, HELLP syndrome), as well as a higher incidence of nonspecific TMAs, such as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, during pregnancy. Significant strides have been taken in understanding the underlying mechanisms of these disorders in the past 40 years. This progress has involved the identification of pivotal factors contributing to TMAs, such as the complement system, ADAMTS13, and the soluble VEGF receptor Flt1. Regardless of the specific causal factor (which is not generally unique in relation to the usual multifactorial origin of TMAs), the endothelial cell stands as a central player in the pathophysiology of TMAs. Pregnancy has a major impact on the physiology of the endothelium. Besides to the development of placenta and its vascular consequences, pregnancy modifies the characteristics of the women's microvascular endothelium and tends to render it more prone to thrombosis. This review aims to delineate the distinct features of pregnancy-related TMAs and explore the contributing mechanisms that lead to this increased susceptibility, particularly influenced by the "gravid endothelium." Furthermore, we will discuss the potential contribution of histopathological studies in facilitating the etiological diagnosis of pregnancy-related TMAs.

Combined usage of serodiagnosis and O antigen typing to isolate Shiga toxin-producing Escherichia coli O76:H7 from a hemolytic uremic syndrome case and genomic insights from the isolate

IMPORTANCE

Hemolytic uremic syndrome (HUS) is a life-threatening disease caused by Shiga toxin-producing Escherichia coli (STEC) infection. The treatment approaches for STEC-mediated typical HUS and atypical HUS differ, underscoring the importance of rapid and accurate diagnosis. However, specific detection methods for STECs other than major serogroups, such as O157, O26, and O111, are limited. This study focuses on the utility of PCR-based O-serotyping, serum agglutination tests utilizing antibodies against the identified Og type, and isolation techniques employing antibody-conjugated immunomagnetic beads for STEC isolation. By employing these methods, we successfully isolated a STEC strain of a minor serotype, O76:H7, from a HUS patient.

A novel scoring system for the prediction of disease severity in STEC-HUS

BACKGROUND

Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) is a life-threatening condition complicated by acute kidney injury, acute respiratory distress syndrome, and central nervous system disorders. The early identification of high-risk patients is required to facilitate timely and appropriate treatment.

METHODS

The medical records of patients with STEC-HUS treated at 11 hospitals in Hokkaido, Japan, were reviewed retrospectively. A multi-institutional retrospective analysis was performed in which patients were divided into two groups according to the presence or absence of severe complications requiring blood purification therapy or encephalopathy. We compared the laboratory values at diagnosis between the severe and mild groups. To identify patients at high risk of developing severe complications, a scoring system, referred to as the "STEC-HUS severity (STEC-HUSS) score," was constructed based on the parameters showing significant differences.

RESULTS

Of the 41 patients with STEC-HUS, 11 were classified into the severe group and 30 into the mild group. Significant differences were observed between the groups in terms of white blood cell count, activated partial thromboplastin time, fibrinogen, D-dimer, total protein, aspartate transaminase, alanine transaminase, lactate dehydrogenase, creatinine, and C-reactive protein levels. The STEC-HUSS score was calculated on a scale of 0-10 by summing the number of test items that demonstrated abnormal values. The STEC-HUSS score, when the cut-off value was 4, showed a sensitivity of 100% and a specificity of 91% in the severe group.

CONCLUSION

We developed a novel scoring system to identify patients at high risk of severe STEC-HUS.

Regulation of human neutrophil IL-1β secretion induced by Escherichia coli O157:H7 responsible for hemolytic uremic syndrome

Shiga-toxin producing Escherichia coli (STEC) infections can cause from bloody diarrhea to Hemolytic Uremic Syndrome. The STEC intestinal infection triggers an inflammatory response that can facilitate the development of a systemic disease. We report here that neutrophils might contribute to this inflammatory response by secreting Interleukin 1 beta (IL-1β). STEC stimulated neutrophils to release elevated levels of IL-1β through a mechanism that involved the activation of caspase-1 driven by the NLRP3-inflammasome and neutrophil serine proteases (NSPs). Noteworthy, IL-1β secretion was higher at lower multiplicities of infection. This secretory profile modulated by the bacteria:neutrophil ratio, was the consequence of a regulatory mechanism that reduced IL-1β secretion the higher were the levels of activation of both caspase-1 and NSPs, and the production of NADPH oxidase-dependent reactive oxygen species. Finally, we also found that inhibition of NSPs significantly reduced STEC-triggered IL-1β secretion without modulating the ability of neutrophils to kill the bacteria, suggesting NSPs might represent pharmacological targets to be evaluated to limit the STEC-induced intestinal inflammation.

A comprehensive model for assessing and classifying patients with thrombotic microangiopathy: the TMA-INSIGHT score

BACKGROUND

Thrombotic Microangiopathy (TMA) is a syndrome characterized by the presence of anemia, thrombocytopenia and organ damage and has multiple etiologies. The primary aim is to develop an algorithm to classify TMA (TMA-INSIGHT score).

METHODS

This was a single-center retrospective cohort study including hospitalized patients with TMA at a single center. We included all consecutive patients diagnosed with TMA between 2012 and 2021. TMA was defined based on the presence of anemia (hemoglobin level < 10 g/dL) and thrombocytopenia (platelet count < 150,000/µL), signs of hemolysis, and organ damage. We classified patients in eight categories: infections; Malignant Hypertension; Transplant; Malignancy; Pregnancy; Thrombotic Thrombocytopenic Purpura (TTP); Shiga toxin-mediated hemolytic uremic syndrome (STEC-SHU) and Complement Mediated TMA (aHUS). We fitted a model to classify patients using clinical characteristics, biochemical exams, and mean arterial pressure at presentation.

RESULTS

We retrospectively retrieved TMA phenotypes using automatic strategies in electronic health records in almost 10 years (n = 2407). Secondary TMA was found in 97.5% of the patients. Primary TMA was found in 2.47% of the patients (TTP and aHUS). The best model was LightGBM with accuracy of 0.979, and multiclass ROC-AUC of 0.966. The predictions had higher accuracy in most TMA classes, although the confidence was lower in aHUS and STEC-HUS cases.

CONCLUSION

Secondary conditions were the most common etiologies of TMA. We retrieved comorbidities, associated conditions, and mean arterial pressure to fit a model to predict TMA and define TMA phenotypic characteristics. This is the first multiclass model to predict TMA including primary and secondary conditions.

Complement System and the Kidney: Its Role in Renal Diseases, Kidney Transplantation and Renal Cell Carcinoma

The crosstalk among the complement system, immune cells, and mediators of inflammation provides an efficient mechanism to protect the organism against infections and support the repair of damaged tissues. Alterations in this complex machinery play a role in the pathogenesis of different diseases. Core complement proteins C3 and C5, their activation fragments, their receptors, and their regulators have been shown to be active intracellularly as the complosome. The kidney is particularly vulnerable to complement-induced damage, and emerging findings have revealed the role of complement system dysregulation in a wide range of kidney disorders, including glomerulopathies and ischemia-reperfusion injury during kidney transplantation. Different studies have shown that activation of the complement system is an important component of tumorigenesis and its elements have been proved to be present in the TME of various human malignancies. The role of the complement system in renal cell carcinoma (RCC) has been recently explored. Clear cell and papillary RCC upregulate most of the complement genes relative to normal kidney tissue. The aim of this narrative review is to provide novel insights into the role of complement in kidney disorders.

Clinical features and outcomes of patients with diacylglycerol kinase epsilon nephropathy: a nationwide experience

BACKGROUND

Thrombotic microangiopathy (TMA) is usually caused due to dysregulation of the alternative complement pathway. Rarely, thrombotic microangiopathy is caused by non-complement mediated mutations in diacylglycerol kinase epsilon (DGKE); information about therapy and outcome of these patients is limited.

METHODS

Medical records of patients, younger than 18 years, diagnosed with TMA and variants in DGKE were reviewed to include 12 patients from seven centers. Genetic studies included targeted exome sequencing and multiplex-ligation dependent probe amplification of CFH-CFHR5.

RESULTS

Patients presented at a median age of 11 (7.5, 12.3) months; all were younger than 2 years. All patients had an infectious prodrome; enteroinvasive, enteropathogenic, and enterotoxigenic Escherichia coli were detected in two patients with diarrhea. Chief features included those of microangiopathic hemolysis (n = 11), microscopic hematuria (n = 10), nephrotic range proteinuria (n = 10), hypoalbuminemia (n = 6), elevated total cholesterol (n = 6), and hypocomplementemia (n = 4). Histopathology showed thrombotic microangiopathy (n = 4), overlapping with membranoproliferative pattern of injury (n = 1). At median 3.3 years of follow-up, significant hypertension and/or proteinuria (40%), relapses (66.7%), and death or progression to CKD (60%) were common. Genetic sequencing showed 13 homozygous and compound heterozygous variants (7 pathogenic, 3 likely pathogenic) located throughout DGKE; 11 variants were novel.

CONCLUSIONS

This case series highlights the need to suspect DGKE nephropathy in young patients with TMA, especially those with severe proteinuria. Medium-term outcomes are unsatisfactory with risk of relapses, progressive kidney failure, and death. A higher resolution version of the Graphical abstract is available as Supplementary information.

Haemolytic uraemic syndrome in children England, Wales, Northern Ireland, and Ireland: A prospective cohort study

Haemolytic uraemic syndrome (HUS) caused by infection with Shiga toxin-producing Escherichia coli (STEC) is a relatively rare but potentially fatal multisystem syndrome clinically characterised by acute kidney injury. This study aimed to provide robust estimates of paediatric HUS incidence in England, Wales, Northern Ireland, and the Republic of Ireland by using data linkage and case reconciliation with existing surveillance systems, and to describe the characteristics of the condition. Between 2011 and 2014, 288 HUS patients were included in the study, of which 256 (89.5%) were diagnosed as typical HUS. The crude incidence of paediatric typical HUS was 0.78 per 100,000 person-years, although this varied by country, age, gender, and ethnicity. The majority of typical HUS cases were 1 to 4 years old (53.7%) and female (54.0%). Clinical symptoms included diarrhoea (96.5%) and/or bloody diarrhoea (71.9%), abdominal pain (68.4%), and fever (41.4%). Where STEC was isolated (59.3%), 92.8% of strains were STEC O157 and 7.2% were STEC O26. Comparison of the HUS case ascertainment to existing STEC surveillance data indicated an additional 166 HUS cases were captured during this study, highlighting the limitations of the current surveillance system for STEC for monitoring the clinical burden of STEC and capturing HUS cases.

Case report: Short-term eculizumab use in atypical HUS associated with Lemierre's syndrome and post-infectious glomerulonephritis

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by genetic abnormalities, infections, autoimmune diseases, drugs, and malignancies. Anti-C5 monoclonal antibody eculizumab is the mainstay of treatment of aHUS caused by the genetic defects of the alternative complement pathway. However, the utility of eculizumab in non-genetic forms of aHUS and the timing of treatment discontinuation remain controversial. Here, we report successful short-term eculizumab use in two young adult patients with aHUS due to rare infectious and autoimmune etiologies: Lemierre's syndrome and post-infectious glomerulonephritis, respectively. Eculizumab was rapidly discontinued in both patients with no aHUS recurrence during long-term follow-up. Considering its favorable safety profile with appropriate meningococcal prophylaxis, eculizumab can be considered as a treatment option for non-genetic aHUS.

A decrease in the incidence of Shiga toxin-related hemolytic uremic syndrome as a cause of kidney transplantation at an argentine referral center

BACKGROUND

In Argentina, Hemolytic uremic syndrome caused by Shiga toxin-producing Escherichia coli (STEC HUS), is the main cause of acute kidney injury and the second cause of end-stage renal disease (ESRD) in children. In recent decades, strategies have been implemented to reduce progression to ESRD, but it is not known whether the cumulative incidence of HUS requiring kidney transplantation (KTx) has decreased. We aimed to determine whether the cumulative incidence of STEC HUS in children undergoing KTx decreased and compared outcomes of HUS-related KTx vs. those related to other etiologies.

METHODS

All patients who underwent KTx at our institution were evaluated. The cohort was divided into quintiles (Q), and we compared the cumulative incidence of HUS-related KTx vs KTx due to other etiologies.

RESULTS

A total of 1000 consecutive KTx were included. The cumulative incidence of HUS-related KTx was 11%. HUS was the second cause of KTx in Q1: 17% (1988-1995); Q2: 13.5% (1996-2003); Q3: 11.5% (2004-2009) and third cause in Q4: 10% (2010-2015) and Q5: 3% (2016-2021). The cumulative incidence of HUS-related KTx decreased in Q4 and Q5 compared to Q1, Q2, and Q3 and the decline was even steeper when comparing Q4 to Q5 (p:0.019). There was no difference in graft survival in patients with HUS vs. congenital anomalies of kidney and urinary tract (CAKUT) but better than in those with focal segmental glomerulosclerosis (FSGS).

CONCLUSIONS

In this cohort, the cumulative incidence of HUS-related KTx decreased, which may have been due to the implementation of nephroprotective strategies.

Metabolism-Mediated Thrombotic Microangiopathy in an Older Patient Without Malnutrition

Vitamin B12 deficiency can cause thrombotic microangiopathy (TMA)-like symptoms such as purpura caused by platelet reduction, general fatigue caused by anemia, and renal and hepatic abnormalities caused by malnutrition. TMA-like symptoms are known as metabolism-mediated TMA (MM-TMA). In MM-TMA, blood cell production is altered, and both pancytopenia and schistocytes appear. The initial presentation of MM-TMA makes it challenging to distinguish between primary and secondary TMA when patients do not present risk factors for malnutrition. We encountered an older female patient with a chief complaint of unconsciousness and loss of appetite for two days. Laboratory tests revealed pancytopenia with schistocytes. Moreover, the laboratory data revealed low serum levels of vitamin B12, indicating MM-TMA. The patient was successfully treated with intravenous vitamin B12 supplementation and discharged home. The patient had atrophic gastritis, which could have impeded the absorption of vitamin B12 from food. Among older patients without prolonged appetite loss, TMA-like symptoms should be investigated as MM-TMA induced by vitamin B12 deficiency, and prompt initiation of appropriate treatment is essential to differentiate between MM-TMA and true TMA.

Case report: Area of focus in a case of malignant hypertension

Malignant hypertension (MH) is characterized by severe hypertension (usually grade 3) associated with fundoscopic changes (flame hemorrhages and/or papilledema), microangiopathy and disseminated intravascular coagulation. In addition encephalopathy, acute heart failure and acute deterioration in renal function may be present. The term "malignant" reflects the very poor prognosis for this condition if untreated. When severe hypertension is associated with hypertension-mediated organ damage (HMOD) a life-threatening situation that requires immediate but careful intervention occurs (hypertensive emergency). In the last few years an increase in the number of patients with malignant hypertension has been observed, especially among those patients with black ethnicity. Limited access to treatment and the poor adherence to anti-hypertensive therapy may contribute to the development of hypertensive emergencies. It is considered appropriate to study patients in order to rule out thrombotic thrombocytopenic purpura and hemolytic uremic syndrome. In fact, the microvascular damage caused by malignant hypertension can favor intravascular hemolysis like Thrombotic Microangiopathies (TMs). TMs may present in three different clinical conditions: typical hemolytic uremic syndrome (HUS), atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP). TMs can arise in the context of other pathological processes, including malignant hypertension.

Streptococcus Pneumoniae Bacteremia with Acute Kidney Injury and Transient ADAMTS13 Deficiency

A 43-year-old woman with a medical history of splenectomy for immune thrombocytopenic purpura was diagnosed with Streptococcus pneumoniae bacteremia. Her initial complaints were fever and more importantly painful extremities that appeared cyanotic. During her hospitalisation, she never developed cardiocirculatory failure but presented acute kidney injury (AKI) with oliguria. Laboratory investigations confirmed AKI with serum creatinine 2.55 mg/dL which peaked at 6.49 mg/dL. There was also evidence for disseminated intravascular coagulation (DIC) with decreased platelet count, low fibrinogen levels, and high D-dimer levels. There were no signs of haemolytic anaemia. The initial ADAMTS13 activity was low (17%) but slowly recovered. Renal function progressively improved with supportive therapy, as opposed to the progressing skin necrosis. The association of DIC and low ADAMTS13 activity may have contributed to the severity of microthrombotic complications, even in the absence of thrombotic microangiopathy as thrombotic thrombocytopenic purpura (TTP) or pneumococcal-associated haemolytic uremic syndrome (pa-HUS).