P0392AHUS ASSOCIATED WITH IGA NEPHROPATHY

Thrombotic Microangiopathy (TMA) is a syndrome characterized by microangiopathic hemolytic anemia (MAHA) and thrombocytopenia. The presence of schistocytes on peripheral smear, a negative Coombs test, elevated lactate dehydrogenase, increased reticulocyte count and low haptoglobin are often the clues for MAHA. The microvascular process often targets vasculature in kidneys, brain, gastrointestinal system, heart, and skin. A timely diagnosis and treatment are often crucial to prevent severe end organ damage and death. TMA is classified into primary and secondary forms. Primary TMA includes TTP and complement mediated or atypical hemolytic uremic syndrome (aHUS), often related to a mutation or deficiency and clinically expressed in the setting of a precipitant condition. Secondary TMA is a manifestation of underlying disorder and can occur in clinical scenarios associated with autoimmune disease, malignancy, infections, SOT (Solid Organ Transplant), pregnancy, HSCT (Hematopoietic Stem Cell Transplantation), medications, or methylmalonic acidemia. Transplant associated TMA (TA-TMA) can be complement mediated or aHUS and could be related to the ischemic reperfusion injury, induction regimen, calcineurin inhibitor (CNI) use, mammalian target of rapamycin (MTOR) inhibitor use, or could be infection related. Cost, access, and turnaround time are often the limitations for certain TTP and complement specific testing. Treatment should not be delayed while waiting for such tests. Treatment must be individualized based on the underlying cause of TMA. Terminal complement blockade utilizing monoclonal antibodies directed against C5 complement is the treatment for complement mediated TMA. C5 inhibitors have also been used successfully in treatment of secondary HUS cases where, unlike aHUS, defects in complement cannot be demonstrated. Such treatment has demonstrated improvement in renal function, MAHA and platelet counts.

Coronavirus disease 2019 (COVID-19) has spread tremendously since its first appearance in December 2019. Infected individuals can experience a wide range of systemic complications, including thrombotic microangiopathy (TMA). Like the other forms of TMA, COVID-19-associated TMA is characterized by thrombocytopenia, hemolytic anemia, and organ failure (such as acute kidney injury). The role of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in COVID-19-associated TMA is most probably dual: it can act either as a trigger to an underlying condition or as a cause of TMA. As opposed to the majority of other reported cases, it may be that in our case COVID-19 was the only cause of TMA. We present a case of a 32-year-old previously healthy man who was treated for acute kidney injury associated with TMA, which we believe was caused by COVID-19. Thrombotic thrombocytopenic purpura, as well as other possible known causes of typical and atypical hemolytic-uremic syndrome, was excluded. During his hospitalization, three negative nasopharyngeal swabs for SARS-CoV-2 were obtained, but serological tests showed the presence of IgG and IgA antibodies. After initial treatment known to be helpful in other forms of TMA (therapeutic plasma exchange and methylprednisolone), his renal function and platelet count recovered completely. Our case illustrates the importance of quickly recognizing this life-threatening complication of COVID-19 and using treatment that has been shown to be beneficial in other forms of TMA. Future studies of the pathophysiology and subsequent targeted treatment of this novel disease are needed.

Background:Atypical hemolytic uremic syndrome (aHUS) is an extremely rare, heterogeneous disease of uncontrolled activation of the alternative complement pathway that is difficult to diagnose. We have evaluated the Canadian patients enrolled in the Global aHUS Registry to provide a Canadian perspective regarding the diagnosis and management of aHUS and the specific challenges faced.Objective:To evaluate Canadian patients enrolled in the Global aHUS Registry to provide a Canadian perspective regarding the diagnosis and management of aHUS and the specific challenges faced.Methods:The Global aHUS Registry is an observational, noninterventional, multicenter study that has prospectively and retrospectively collected data from patients of all ages with an investigator-made clinical diagnosis of aHUS, irrespective of treatment. Patients of all ages with a clinical diagnosis of aHUS were eligible and invited for enrollment, and those with evidence of Shiga toxin–producing Escherichia coli infection, or with ADAMTS13 activity ≤10%, or a subsequent diagnosis of thrombotic thrombocytopenic purpura were excluded. Data were collected at enrollment and every 6 months thereafter and were analyzed descriptively for categorical and continuous variables. End-stage renal disease (ESRD)-free survival was evaluated using Kaplan-Meier estimates, and ESRD-associated risk factors of interest were assessed using Cox proportional hazards regression models. Patients were censored at start of eculizumab for any outcome measures.Results:A total of 37 Canadian patients were enrolled (15 pediatric and 22 adult patients) between February 2014 and May 2017; the median age at initial aHUS presentation was 25.9 (interquartile range = 6.7-51.7) years; 62.2% were female and 94.6% had no family history of aHUS. Over three-quarters of patients (78.4%) had no conclusive genetic or anti-complement factor H (CFH) antibody information available, and most patients (94%) had no reported precipitating factors prior to aHUS diagnosis. Nine patients (8 adults and 1 child) experienced ESRD prior to the study. After initial presentation, there appears to be a trend that children are less likely to experience ESRD than adults, with 5-year ESRD-free survival of 93 and 56% (P = .05) in children and adults, respectively. Enrolling physicians reported renal manifestations in all patients at initial presentation, and 68.4% of patients during the chronic phase (study entry ≥6 months after initial presentation). Likewise, extrarenal manifestations also occurred in more patients during the initial presenting phase than the chronic phase, particularly for gastrointestinal (61.1% vs 15.8%) and central nervous system sites (38.9% vs 5.3%). Fewer children than adults experienced gastrointestinal manifestations (50.0% vs 70.0%), but more children than adults experienced pulmonary manifestations (37.5% vs 10.0%).Conclusions:This evaluation provides insight into the diagnosis and management of aHUS in Canadian patients and the challenges faced. More genetic or anti-CFH antibody testing is needed to improve the diagnosis of aHUS, and the management of children and adults needs to consider several factors such as the risk of progression to ESRD is based on age (more likely in adults), and that the location of extrarenal manifestations differs in children and adults.

Атипичный гемолитикоуремический синдром (аГУС) ультраредкое (орфанное) заболевание прогрессирующего течения, представляющее собой системную тромботическую микроангиопатию (ТМА) вследствие хронической неконтролируемой активации альтернативного пути комплемента. В настоящее время установлено, что генетические аномалии комплемента, которые раньше рассматривали как основную причину заболевания, являются лишь фактором, предрасполагающим к возникновению ТМА. Классическую триаду клинических проявлений аГУС составляют тромбоцитопения, микроангиопатическая гемолитическая анемия и острое повреждение почек. У большинства пациентов независимо от возраста отмечается артериальная гипертензия, основными причинами которой являются гиперренинемия вследствие ишемии ткани почек, обусловленной ТМА, и перегрузка объемом при наличии олиго/анурии. Атипичный ГУС представляет собой системную ТМА, при которой могут поражаться не только почки, но и другие жизненно важные органы головной мозг, сердце, легкие, пищеварительный тракт, глаза и др. Диагноз аГУС это диагноз исключения. Он устанавливается на основании характерной клинической картины после исключения других форм ТМА, как первичных, так и вторичных. Для исключения тромботической тромбоцитопенической пурпуры (ТТП) всем больным с ТМА необходимо определение активности ADAMTS13: снижение ее до 10 и менее является диагностическим маркером ТТП. У пациентов с аГУС и другими ТМА активность ADAMTS13 может быть снижена, однако всегда превышает 10. Инновационным подходом к лечению аГУС, используемым в клинической практике в течение последнего десятилетия, стало применение экулизумаба препарата группы комплеменингибирующих антител, который является препаратом патогенетической терапии аГУС. Экулизумаб является средством первой линии для лечения детей с установленным диагнозом аГУС, при семейном характере заболевания, наличии экстраренальных проявлений. Совершенствование методов диагностики и внедрение новых подходов к лечению позволяет быстрее заподозрить и купировать проявления аГУС, добиться стойкой ремиссии и улучшить прогноз. Atypical hemolytic uremic syndrome (aHUS) is an ultra rare (orphan) progressive disease that is a systemic thrombotic microangiopathy (TMA) due to chronic uncontrolled activation of the alternative complement pathway. It is currently established that complement genetic abnormalities that were previously considered the main cause of the disease, are only a factor predisposing to TMA occurrence. The classic triad of aHUS clinical manifestations is thrombocytopenia, microangiopathic hemolytic anemia andacute kidney damage. Most patients, regardless of age, have arterial hypertension the main reasons of hypertension are hyperreninemia (due to kidney tissue ischemia because of TMA) and volume overload in the presence of oligo/anuria. Atypical HUS is a systemic TMA that affected not only the kidneys, but also other vital organs brain, heart, lungs, digestive tract, eyes, etc. The diagnosis of aHUS is a diagnosis of exclusion that is established on the basis of specifi c clinical picture after exclusion of other forms of TMA, both primary and secondary. To exclude thrombotic thrombocytopenic purpura (TTP), all patients with TMA need to determine ADAMTS13 activity: its reducing to 10 or less is a diagnostic marker of TTP. In patients with aHUS and other TMA, ADAMTS13 activity may be reduced, but always exceeds 10. The innovative pathogenetic approach to aHUS treatment over the last decade became the application of eculizumab that is a drug from complementinhibitory antibodies group. Eculizumab is a fi rstline treatment for children with proven aHUS diagnosis, with familial disease, with extrarenal manifestations. Progress in diagnostic methods and new treatment approaches allows us to quickly suspect and stop the manifestations of aHUS, achieve stable remission and improve the prognosis.

MAC Plus Study: A Retrospective Study Correlating DNA Variants, Clinical Course and Outcomes from 187 Patients Who Underwent Testing Using an Atypical Hemolytic Uremic Syndrome and Thrombotic Microangiopathy Genetic Sequencing Panel

Introduction: More reports of thrombotic microangiopathy (TMA) in immunoglobulin A (IgA) nephropathy suggest its association with poor clinical outcomes. However, the prevalence and clinical significance of TMA in IgA nephropathy have not been widely studied in different populations. Methods: Kidney biopsies of all patients with primary IgA nephropathy from 1995 to 2015 at the King Chulalongkorn Memorial Hospital, Thailand, were retrospectively reviewed and reclassified by two pathologists following the Oxford MEST-C classification. TMA lesions were detected based solely on light microscopic findings. Associations between the presence of TMA and clinical data, other pathologic findings, and clinical outcomes were studied. Results: Among 267 patients with primary IgA nephropathy, 166 had adequate clinical data and kidney tissues for the analysis. TMA was observed in 21 patients (13%) and was associated with higher mean arterial pressure (MAP), history of malignant hypertension, higher proteinuria, and lower estimated glomerular filtration rate (eGFR) at diagnosis compared to those without TMA. According to the Oxford MEST-C classification, TMA showed a significant association with severe tubular atrophy/interstitial fibrosis (T2) but not with mesangial hypercellularity (M1), endocapillary hypercellularity (E1), segmental glomerulosclerosis (S1), or crescents (C1–2). After a median follow-up of 50 months, patients with TMA had a significantly higher risk of progression to end-stage kidney disease (ESKD) (hazard ratio [HR] 5.8, 95% confidence interval [CI]: 3.1–10.9) and all-cause mortality (HR 3.4, 95% CI: 1.3–8.8). After adjusting for baseline eGFR, MAP, proteinuria, and other pathological lesions, TMA remained an independent predictor of ESKD (adjusted HR 2.4, 95% CI: 1.1–5.4). Conclusions: Kidney TMA in IgA nephropathy is associated with advanced disease stages, carries a poor prognosis, and thus should be considered in the pathological classification of IgA nephropathy.

When faced with microangiopathic haemolytic anaemia, thrombocytopenia and organ dysfunction, clinicians should suspect thrombotic microangiopathy (TMA). The endothelial damage that leads to this histological lesion can be triggered by several conditions or diseases, hindering an early diagnosis and aetiological treatment. However, due to systemic involvement in TMA and its low incidence, an accurate early diagnosis is often troublesome. In the last few decades, major improvements have been made in the pathophysiological knowledge of TMAs such as thrombotic thrombocytopenic purpura [TTP, caused by ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin Type 1 motif, member 13) deficiency] and atypical haemolytic uraemic syndrome (aHUS, associated with dysregulation of the alternative complement pathway), together with enhancements in patient management due to new diagnostic tools and treatments. However, diagnosis of aHUS requires the exclusion of all the other entities that can cause TMA, delaying the introduction of terminal complement blockers, which have shown high efficacy in haemolysis control and especially in avoiding organ damage if used early. Importantly, there is increasing evidence that other forms of TMA could present overactivation of the complement system, worsening their clinical progression. This review addresses the diagnostic and therapeutic approach when there is clinical suspicion of TMA, emphasizing complement evaluation as a potential tool for the inclusive diagnosis of aHUS, as well as for the improvement of current knowledge of its pathophysiological involvement in other TMAs. The development of both new complement activation biomarkers and inhibitory treatments will probably improve the management of TMA patients in the near future, reducing response times and improving patient outcomes.

We present a rare case of IgA nephropathy in a patient who developed atypical hemolytic uremic syndrome (aHUS) associated with a complement factor H (CFH) gene mutation, and who was successfully treated with eculizmab. A 76-year-old man was admitted as the patients had thrombotic microangiopathies findings. The patient was treated with plasma exchange, hemodialysis and methylprednisolone. A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 level was not decreased. Light microscopy findings were consistent with hemolytic uremic syndrome and immunofluorescence analysis revealed IgA and C3 were detected. Genetic analysis revealed that mutation of p.Arg1215Gln in CFH was identified. The diagnosis of aHUS was confirmed and eculizmab therapy was currently effective for 5 months.

The current narrative review study aims to provide an overview of thrombotic microangiopathy (TMA) in immunoglobulin A nephropathy (IgAN), with a particular emphasis on its pathophysiology, histopathology, and treatment options. The prevalence and clinical significance of TMA in IgAN may vary across different populations. Estimates suggest that TMA events occur in 2-50% of patients with IgAN. Endothelial injury is a key factor in TMA development in IgAN, triggered by immune complex deposition, complement activation, and potentially hypertension. TMA in IgAN correlates with vascular lesions, including arterial intimal sclerosis, arteriolar lumen reduction, and smooth muscle hypertrophy. Notably, patients with TMA show more intense deposition of C4, C3d, and C5b-9 complements. Treatment involves blood pressure management, immunosuppression, and targeted therapies such as eculizumab.

Thrombotic microangiopathy (TMA) is a complication of malignant hypertension (mHTN) attributed to high blood pressure (BP). However, no studies have investigated in patients with mHTN of different aetiologies whether the presence of TMA is associated with specific causes of mHTN. We investigated the presence of TMA (microangiopathic haemolytic anaemia and thrombocytopenia) in a large and well-characterized cohort of 199 patients with mHTN of different aetiologies [primary HTN 44%, glomerular diseases 16.6%, primary atypical haemolytic uraemic syndrome (aHUS) 13.1%, renovascular HTN 9.5%, drug-related HTN 7%, systemic diseases 5.5%, endocrine diseases 4.5%]. Outcomes of the study were kidney recovery and kidney failure. Patients with TMA [40 cases (20.1%)] were younger, were more likely female and had lower BP levels and worse kidney function at presentation. Their underlying diseases were primary aHUS (60%), drug-related mHTN (15%), glomerular diseases [all of them immunoglobulin A nephropathy (IgAN); 10%], systemic diseases (10%) and primary HTN (5%). The presence of TMA was 92.3% in primary aHUS, 42.9% in drug-related HTN, 36.4% in systemic diseases, 12.1% in glomerular diseases and 2.3% in primary HTN. No patient with renovascular HTN or mHTN caused by endocrine diseases developed TMA, despite BP levels as high as patients with TMA. A higher proportion of TMA patients developed kidney failure as compared with patients without TMA (56.4% versus 38.9%, respectively). The presence of TMA in patients with mHTN should guide the diagnosis towards primary aHUS, drug-related mHTN, some systemic diseases and IgAN, while it is exceptional in other causes of mHTN.

Objective: To evaluate the clinical approach, the diagnostic method and the most appropriate therapeutic management of thrombotic microangiopathies (TMA) in pregnancy, still leading killers in the obstetric area today. Materials and methods: A large review of the international literature and available clinical studies has been carried out in order to define the current state of the art regarding TMA in pregnancy. In the light of this, 9 clinical cases, among 152 TMA cases, of pregnant women hospitalized and who gave birth in the Pisa University Hospital O.O. U.U. Gynecology and Obstetrics 1 and 2 from 2010 to 2019, were identified, analyzed and re-discussed. Results: Analyzing the diagnostic method and the medical records, we made a critical review of these 9 cases, accurately analyzing the diagnoses made. Among these cases, 6 Thrombotic Thrombocytopenic Purpura (TTP), 2 HELLP Syndrome and 1 Atypical Hemolytic Uremic Syndrome (aHUS) were diagnosed during pregnancy. By analyzing the medical records, the diagnostic method and the therapeutic management of these patients, we questioned the diagnoses made. These diagnoses, from our analytical point of view, are partially not corresponding, being 4 cases of TTP and 5 possible cases of aHUS. Conclusion: From the review of our case history, in the Pisa Obstetric clinics, it is possible to find an under diagnosis of the aHUS cases compared to those of TTP and HELLP syndrome, due both to the unavailability of the ADAMTS13 functionality test and to the unused LDH/AST ratio, which in our opinion could represent a future resource in diagnostic approach to thrombotic microangiopathies in pregnancy.

Immunoglobulin A nephropathy (IgAN) or Berger's disease is the most common form of primary glomerulonephritis in the world and one of the first causes of end-stage renal failure. IgAN is characterized by the accumulation of immune complexes containing polymeric IgA1 in mesangial areas. The pathogenesis of this disease involves the deposition of polymeric and hypogalactosylated IgA1 (Gd-IgA1) in the mesangium. Quantitative and structural changes of Gd-IgA1 play a key role in the development of the disease due to functional abnormalities of two IgA receptors: the FcαRI (CD89) expressed by blood myeloid cells and the transferrin receptor (CD71) on mesangial cells. Abnormal Gd-IgA1 induces release of soluble CD89, which participates in the formation of circulating IgA1 complexes. These complexes are trapped by CD71 that is overexpressed on mesangial cells in IgAN patients together with the crosslinking enzyme transglutaminase 2 allowing pathogenic IgA complex formation in situ and mesangial cell activation. A humanized mouse model expressing IgA1 and CD89 develops IgAN in a similar manner as patients. In this model, a food antigen, the gliadin, was shown to be crucial for circulating IgA1 complex formation and deposition, which could be prevented by a gluten-free diet. Identification of these new partners opens new therapeutic prospects for IgAN treatment.

For further investigations in IgA nephropathy the approach from phenotype to genotype is welcome.

Phenotypic expression of factor H mutations in patients with atypical hemolytic uremic syndrome

Deposition of polymeric IgA1 (pIgA) in kidney mesangium is the hallmark of IgA nephropathy (IgAN). Current consensus is that a fraction of IgA1 molecules in the circulation of IgAN patients exhibit aberrant structures or properties that may lead to their deposition. Our previous findings suggest that the anionic property of IgA1 may play a role in mesangial IgA1 deposition in patients with IgAN. In the present study, the functional consequences of the binding of anionic polymeric IgA1 to human mesangial cells (HMCs) were investigated. Anionic polymeric IgA1 from IgAN patients and healthy subjects was isolated by sequential jacalin affinity chromatography, size exclusion chromatography using size exclusion and MonoQ ion exchange chromatography. HMCs were cultured with purified anionic polymeric IgA1 and the release of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) was examined by enzyme-linked immunosorbent assay. The signalling pathways involved in anionic pIgA-mediated HMC activation were examined by immunoblotting. Standard electrophoretic mobility shift assay (EMSA) was used to further examine whether the transcriptional factor NF-kappaB is associated in the signalling process. To define the mechanism of TNF-alpha and IL-6 production, HMCs were cultured with anionic pIgA in the presence or absence of p42/p44 mitogen-activated protein kinase (MAPK) inhibitor (PD98059), NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC) or NF-kappaB blocking permeable peptides. Compared with less anionic pIgA or monomeric IgA1 (mIgA), anionic pIgA from patient with IgAN significantly increased cell proliferation (P<0.05) when cultured with HMC. These anionic pIgA significantly increased the synthesis of TNF-alpha (P<0.05) and IL-6 (P<0.05) in a dose and time-dependent manner. Furthermore, the increased synthesis of IL-6 and TNF-alpha by anionic pIgA in HMC was significantly diminished (P<0.01) in the presence of NF-kappaB inhibitor pyrrolidine dithiocarbamate and NF-kappaB blocking permeable peptides SN50 (P<0.01). The increased synthesis of IL-6 by anionic pIgA in HMC was reduced by inhibitor to NF-kappaB or p42/p44 MAPK and was abolished by the simultaneous presence of inhibitors to p42/p44 MAPK and NF-kappaB. The up-regulation of TNF-alpha was partially suppressed by inhibitor to NF-kappaB but not PD98059. Our results suggest that polymeric anionic IgA1 could activate HMC and increase the synthesis of TNF-alpha and IL-6. While both the p42/p44 MAPK and NF-kappaB pathways are essential in regulating the anionic pIgA-induced synthesis of IL-6, TNF-alpha synthesis mediated by anionic pIgA is partly dependent on NF-kappaB.