Chronic Thrombotic Microangiopathy Research Articles

#198 Different patterns of renal thrombotic microangiopathy

Abstract Background and Aims Thrombotic microangiopathy (TMA) is a renal lesion often associated with microangiopathic hemolysis. However, there are cases of TMA that present without hemolysis, hematuria or even proteinuria, sometimes being an incidental histopathological finding. In these situations, little is known about the long-term effects on renal function. The aim of our study is to describe the clinical and histopathological presentation of patients with renal TMA biopsied in our center, focusing on those without hemolysis and with low clinical suspicion of TMA. Method We conducted a retrospective observational unicentric study. Clinical and histological parameters were collected from patients biopsied between 2015 and 2023, whose renal biopsy (RB) showed TMA, with a minimum follow-up of 6 months. We excluded renal transplant recipients. Results Data were collected from 41 patients (17 men, 24 women), with a mean age at the time of RB of 54 ± 16 years and a mean eGFR of 80 ± 23 ml/min/1.72 m2. 12 of them (29%) had chronic kidney disease (CKD). Twenty-seven patients (66%) did not have hemolysis at diagnosis. Compared to patients with hemolysis, they were of older age (58 vs 47 years, p = 0.030) and had higher prevalence of CKD (41% vs 7%, p = 0.028). They had a milder clinical presentation, with lower creatinine (168 vs 419 μmol/L, p = 0.029), lower need for renal replacement therapy (RRT) (4% vs 50%, p = 0.001), less hematuria (33% vs 79%, p = 0.008) and proteinuria (67% vs 100%, p = 0.035). Histologically, patients without hemolysis had less fibrosis (56% vs 86%, p = 0.084) and fewer chronic TMA lesions (double contours, wrinkling of the basement membrane) (52% vs 93%, p = 0.009), despite delayed renal biopsy compared to patients with hemolysis (99 ± 118 vs 28 ± 30 days since clinical presentation, p = 0.036). The causes of TMA that were most commonly associated with the absence of hemolysis were drugs (89% without hemolysis) and glomerulopathies such as IgA nephropathy, minimal change disease and fibrillary glomerulonephritis (100% without hemolysis). Within this group of patients without hemolysis, 13 (32%) had a low clinical suspicion of TMA, defined as the absence of hemolysis, hypertension and predisposing factors, in some cases being an incidental finding in the RB. As expected, they also had a mild presentation and did not require RRT. In some cases, they even presented without proteinuria (7 patients, 64%). When comparing the severity of the lesions in renal tissue with patients with high clinical suspicion of TMA, patients with low clinical suspicion presented a similar prevalence of mesangiolysis, vascular damage and a similar proportion of affected glomeruli. Chronic TMA lesions were present in both groups (Table 1). When analysing the evolution of renal function, there are several confounding factors to consider (higher prevalence of CKD in patients without hemolysis, targeted treatment in patients with hemolysis, different time of follow-up between groups...). In our results, there were no statistically significant differences in the evolution of creatinine and proteinuria between groups, even when TMA was an incidental finding. In our sample, these findings were not attributable to a larger number of other histopathological lesions in patients with low suspicion of TMA, as there were no differences between groups (see Table 1). Conclusion Renal TMA should be suspected even in the absence of hemolysis, hypertension or proteinuria, as in our sample one third of diagnoses were incidental and their mild presentation may have delayed renal biopsy. The severity of histological lesions and the evolution of renal function in these cases are comparable to those of patients with a high clinical suspicion. Therefore, its prompt identification, etiological study and treatment are equally important. Currently, we have insufficient data to provide the different clinical scenarios in which TMA should be suspected. However, based on our findings, in the presence of drugs TMA should be considered in the differential diagnosis along with Acute Interstitial Nephritis, even in the absence of urinary abnormalities.

Hydralazine use can be associated with IgM-dominated immune complex-mediated glomerulonephritis

ABSTRACT Context IgM-dominant immune complex-mediated glomerulonephritis (IgM-dominant ICMGN) is a rare renal entity, characterized by a membranoproliferative pattern by light microscopy, dominant IgM staining by immunofluorescent staining, and subendothelial deposits by electron microscopy. This study was to investigate if some of IgM-ICMGN were associated with autoimmune disorders induced by hydralazine. Design Seven IgM-dominant ICMGN cases were identified over 8 years. Their pathologic phenotypes and clinical scenarios were analyzed in detail. Results Patients’ ages ranged from 47 to 87 years old with 5 women and two men. Six of seven patients had drug-induced autoimmune phenomenon (hydralazine-induced positive ANCA and ANA). All of them had renal dysfunction and some proteinuria. Most pathologic features showed a membranoproliferative pattern of glomerulonephritis with dominant IgM deposits at subendothelial spaces. IgM nephropathy (a variant of focal segmental glomerulosclerosis), chronic thrombotic microangiopathy, and cryoglobulinemic glomerulopathy were ruled out in the cases. Conclusion The hydralazine-induced autoimmune phenomenon can be seen in IgM-dominant ICMGN, which should be classified as a subtype of membranoproliferative glomerulonephritis.

#4808 DIFFERENTIATING POSTPARTUM HELLP SYNDROME FROM ATYPICAL HEMOLYTIC UREMIC SYNDROME

Abstract Background and Aims HELLP (hemolysis, elevated liver enzymes, low platelets) is a severe variant of preeclampsia whose pathogenesis remains unknown but likely involves abnormal placentation, endothelial dysfunction and release of vasoactive substances. Complement dysregulation is implicated in the pathogenesis of atypical hemolytic uremic syndrome (aHUS) and there is growing evidence to support its role in HELLP syndrome. Here we present a case of postpartum thrombotic microangiopathy (TMA) in the setting of HELLP syndrome. Method We present a case report. Ethics approval was obtained by the Queen's University Health Sciences and Affiliated Teaching Hospitals Research Ethics Board. Results A 22 year old G1P1 Caucasian woman presents at 37 weeks gestation with abdominal pain and severe hypertension. Labs demonstrated TMA including hemoglobin 95, platelets 30, LDH 2597, and schistocytes. She had severe transaminitis with AST 1845 and ALT 830, and proteinuric acute kidney injury. She was diagnosed with HELLP syndrome and treated with anti-hypertensives and emergency Caesarean section. Unfortunately, the infant did not survive, and there was no placental abruption. Platelets recovered by day 5 postpartum, LDH by day 7. However, renal function worsened and by day 6 postpartum, she required hemodialysis. A renal biopsy revealed acute and chronic TMA. She did not have cortical necrosis. Further workup revealed normal C3, C4 and ADAMTS13 levels. Dialysis was stopped after two weeks. By 6 months, her renal function and proteinuria returned to normal. Complement function testing revealed negative complement factor H autoantibody, but elevated soluble C5b-9 (sC5b-9) level (0.42 mg/L, normal <0.3). Ex-vivo serum C5b-9 deposition on human microvascular endothelial cells was assessed both on resting (182%, normal <150%) and on ADP-activated endothelial cells (273%, normal <150%). This test was repeated 6 months postpartum when renal function had normalized, and results were persistently abnormal both on resting (215%, normal <150%) and on ADP-activated endothelial cells (282%, normal <150%). aHUS genetic testing was negative. Conclusion Results from Burwick et al suggest that this patient had a very high likelihood of clinical aHUS in association with HELLP syndrome (elevated LDH >1832 U/L and creatinine >1.9 mg/dL) [1]. Identifiable aHUS genetic mutations only occur in 50% of aHUS patients. Complement function testing is not routinely assessed for postpartum HELLP; however, the severity of her HELLP syndrome prompted further investigation (C5b-9 deposition testing). The persistence of increased C5b-9 deposition 6 months postpartum for this patient mimics the findings of patients who have confirmed aHUS [2]. Our patient's unique results suggest the patient may be at risk for recurrent TMA/aHUS in her lifetime, particularly if another pregnancy is being considered. Future research should explore which pregnancy associated TMA patients may benefit from anti-complement therapy.

#5990 COMPLEMENT GENES PROFILE OF PATIENTS WITH SEVERE HYPERTENSION AND RENAL THROMBOTIC MICROANGIOPATHY

Abstract Background and Aims Hereditary or acquired complement system dysregulation found to be driving cause of endothelial damage in atypical haemolytic uremic syndrome (aHUS) – ultrarare life-threatening disease, that always manifests with renal thrombotic microangiopathy (TMA), resulting in poor outcome in absence of appropriate treatment. Nevertheless, several studies show high incidence of rare genetic variants of complement system in other TMA’s, including hypertension-induced TMA. Here we report results of complement genes screening in patients (pts) with histologically identified renal TMA and severe hypertension in Russia, at first diagnosed as hypertension-induced TMA. Method A total of 28 Caucasian pts diagnosed with renal TMA (confirmed by kidney biopsy in all cases) and severe hypertension enrolled in the study. The main characteristic of the clinical picture was the absence of microangiopathic hemolysis and thrombocytopenia in prevailing of the pts, thus most of the primary and secondary causes of TMA clinically excluded. Examination of DNA samples was performed in all pts using next generation sequencing (NGS) technology. For statistical analysis continuous variables were presented as Mean (±Standart deviation) or Median (interquartile range) as appropriate. Results Baseline demographic and clinical characteristics of group are listed in Table 1. 13 pts (46%) had malignant form of hypertension (MHT) confirmed by eye examination. Mean systolic arterial pressure (SAP) observed at the time of presentation was 210±29 mmHg, mean diastolic arterial pressure (DAP) was 122±19 mmHg. Kidney morphology revealed chronic TMA lesions in 12 pts (43%), acute and chronic alterations simultaneously detected in 13 pts (46%). Predominantly acute lesions with glomerular and extraglomerular thrombi found in 3 (11%) pts only. Complement genes abnormalities revealed in 7 (25%) out of 28 pts. Complement factor I (CFI) rare variants were found in 2 pts (CFI c. 772<A, CFI c.1217G>A), one of this pts also had additional variant in complement factor H related protein 4 (CFHR4 c.766G>A). Complement factor C3 rare variant was observed in 1 pt (C3 c.2203C>T), membrane cofactor protein (MCP or CD46) rare variant in 1 pt (CD46 c. 198A>T), complement factor H related protein 5 (CFHR5) variant detected in 1 pt (CFHR5 c.136C>T), homozygous deletion of CFHR1 and CFHR3 detected in 1 pt and heterozygous deletion of the same complement factor H related protein genes found in another pt. Conclusion A quarter of pts with TMA and severe hypertension may have genetic defects in the complement system. These results confirmed that complement-mediated HUS may be misdiagnosed as hypertension-induced TMA. Lack of convincing hematological signs of TMA is common in this group, making aHUS diagnosis more sophisticated.

Kidney Biopsy in a Patient with Cardiorenal Metabolic Syndrome—How to Interpret Histopathology

The components of Cardiorenal Metabolic Syndrome (CRMS) include central obesity, insulin resistance, hypertension, metabolic dyslipidemia, proteinuria, and/or reduced glomerular filtration rate. Kidney biopsy is rarely performed in patients with CRMS; histopathology findings include glomerulopathy, podocytopathy, mesangial expansion and proliferation, glomerular basement thickening, global and segmental sclerosis, interstitial fibrosis and tubular atrophy, and arterial sclerosis and hyalinosis. We report a case of CRMS with slow progression during 10 years of follow-up on chronic kidney disease (CKD). The middle-aged patient had central obesity, hypertension, dyslipidemia, cardiovascular disease, type 2 diabetes mellitus, proteinuria, and CKD stage G3b-G4. Kidney biopsy, performed 3 years after the first presentation, led to the diagnosis of chronic thrombotic microangiopathy (TMA) and complement-associated glomerulopathy. This was not compatible with the medical history and the course of the disease, and previous kidney biopsy review showed metabolic nephropathy with glomerulomegaly, global and segmental glomerulosclerosis, tubular atrophy and interstitial fibrosis, arteriosclerosis, and lipid embolus in the lumen of one artery, and found neither TMA features nor C3 deposition. The reported case demonstrates the importance of an accurate and thoughtful reading and interpretation of kidney biopsy, and stresses that disregarding medical history may potentially mislead and alter the understanding of the true cause of CKD.

Ravulizumab in Preemptive Living Donor Kidney Transplantation in Hereditary Atypical Hemolytic Uremic Syndrome.

Dear editor, we here report the first case of successful living donor kidney transplantation using complement inhibition by ravulizumab in a 33-y-old woman suffering from hereditary atypical hemolytic uremic syndrome (aHUS). Atypical HUS is the prototype for complement-mediated diseases that typically present with acute renal failure, albuminuria, and hematological abnormalities.1 In 2018, our patient developed acute-on-chronic kidney failure and increasing albuminuria during her first pregnancy. A stable chronic kidney disease with elevated serum creatinine and albuminuria of unknown cause was already diagnosed in 2004 (Figure 1). Arterial hypertension was well controlled by angiotensin-converting enzyme inhibitors. After premature delivery because of kidney failure and albuminuria, we performed a kidney biopsy. We identified a double contour appearance of capillary walls as one hallmark of chronic thrombotic microangiopathy, thus confirming the diagnosis of aHUS. Interstitial fibrosis was estimated to be about 40%. We rapidly initiated complement inhibition with eculizumab, a C5 inhibitor.2 Although detection of a specific risk mutation is not essential to the clinical diagnosis of aHUS, 50% to 70% of patients show one or more of numerous known genetic alterations.3 In this case, genetic testing revealed a heterozygous variant in the complement factor H (CFH) gene (c.157C>T p.(Arg53Cys)). CFH is an essential inhibitory part of the complement cascade, accelerating the decay of the C3 convertase with >100 reported genetic mutations.4 Mutations in CFH correlate with early onset of disease and worse renal prognosis.4,5 In 2020, a phase 3 study on ravulizumab, a new anti-C5 antibody, demonstrated improved hematological and renal outcomes in aHUS.6 Ravulizumab was engineered from eculizumab but allows recycling of the antibody to expand the half-life compared with eculizumab.7 In consent with our patient, we switched from eculizumab to ravulizumab because of its time-saving infusion interval of once every 8 wk to support our young patient and mother of a small child continuing her university studies. Renal anemia and metabolic acidosis subsequently forced us to prepare our patient for kidney transplantation. Before eculizumab was introduced, renal transplantation of aHUS patients was challenging, and the renal prognosis was poor because of 50% to 90% recurrence rates. Patients with CFH mutations reached the highest relapse rates of thrombotic microangiopathy.8 As eculizumab demonstrated efficacy after kidney transplantation in aHUS and ravulizumab shares its mechanism, we expected noninferiority compared with eculizumab and continued ravulizumab treatment during transplantation, which was performed without shifting infusion intervals.9 In April 2021, the patient received kidney donation from her 30-y-old husband. S-creatinine and albuminuria rapidly declined after transplantation. Neither hematological parameters nor kidney biopsy 2 wk after transplantation revealed signs of thrombotic microangiopathy. Six months after transplantation, the patient presents with stable creatinine and no albuminuria. Given concerns of safety or on drug interactions, clinicians might hesitate to use ravulizumab in patients who progress to end-stage kidney disease and are candidates for living donation transplantation. Hence, patients might be deprived of the benefit from the extended half-life of this drug. To our knowledge, usage of ravulizumab has not been reported for patients undergoing renal transplantation. Thus, we provide first evidence for the efficacy of ravulizumab to prevent recurrence of aHUS in a genetically high-risk situation before and after renal transplantation.FIGURE 1.: Time course of the patient’s medical history depicting the course of serum creatinine (red circles), albuminuria (blue circles), duration of pregnancy (bright yellow square), time points of kidney biopsies (arrows pointing down), start of treatment with eculizumab (E) and ravulizumab (R), and time point of kidney transplantation (arrows pointing left and right).

Renal post-mortem findings in myeloproliferative and myelodysplastic/myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a heterogeneous group of hematological disorders presenting with an increased proliferation in one or several hematological cell lines. Renal manifestations of MPN have not been fully characterized so far. To morphologically assess the potential renal involvement in MPN patients, we analyzed histomorphological findings of a post-mortem cohort (n = 57) with a disease history of Philadelphia-negative MPN including polycythaemia vera, primary myelofibrosis, essential thrombocythemia, or chronic myelomonocytic leukemia (CMML). Seven (12.2%) patients presented with a pattern of diffuse glomerulosclerosis not attributable to diabetic or hypertensive nephropathy. Weak C4d staining suggestive for chronic thrombotic microangiopathy (TMA) was observed in 4/7 cases. Glomerulonephritis was excluded by light microscopy and immunohistochemistry. Patients with a pattern of diffuse glomerulosclerosis did not differ from the rest of the cohort regarding MPN subtype, disease duration, age, or sex. No significant proteinuria had been observed before death. Further findings attributed to MPNs were extramedullary hematopoiesis (n = 5; 8.8%) and tumor involvement in advanced disease (n = 4; 7.0%). Other common findings included arteriolosclerosis (n = 18; 31.6%) and signs of shock (n = 8; 14.0%). To our knowledge, this study is so far the largest investigating renal findings in MPN patients. There may be a causal relationship between idiopathic diffuse glomerular sclerosis and MPN, although its clinical significance and pathophysiology remain uncertain with TMA probably being relevant in a subgroup of cases. Our findings demonstrate the spectrum of renal findings in MPN from early to terminal disease of which hematologists should be aware of in daily clinical practice.

MO237A SERUM COMPLEMENT ABNORMALITY REVEALED BY THROMBOTIC MICROANGIOPATHY DURING INTERFERON TREATMENT OF MULTIPLE SCLEROSIS

Abstract Background and Aims Multiple sclerosis (MS) is a chronic and potentially disabling disease of the central nervous system and is the leading cause of non-traumatic neurological disability in young adults. Beta interferons (IFN-β) are the most-widely prescribed medications for this disease. Despite good overall long-term safety data with prolonged use of this group of drugs, they can rarely cause serious and sometimes life threatening adverse effects. We report a case of thrombotic microangiopathy (TMA) in a patient treated with IFN-β-1a for 03 years. The serum complement study revealed a decrease in Factor I. Method Case report Results A 28-year-old man was diagnosed with relapsing remitting multiple sclerosis in 2007. Subcutaneous IFNβ-1a 44 μg was commenced three times a week in 2017. He had not had a relapse since 2012. In July 2020, he was admitted to intensive care unit for a status epilepticus associated with severe arterial hypertension and then transferred to our department for management of malignant arterial hypertension with acute renal failure.On examination, he did not present any neurological disorder but had very unbalanced blood pressure under triple therapy. Biology had shown an hemoglobin at 9, 7 g / dl; no thrombocytopenia with a collapsed haptoglobin, very high LDH with absence of schizocytes, positive non-specific ANCA and proteinuria at 7g/24hour. The renal puncture biopsy showed chronic vascular and glomerular TMA with IgG and fibrinogen deposits. The course was marked by the rapid deterioration of renal function. The patient received flash corticosteroid therapy 10 mg / kg IV for 3 consecutive days switched to oral corticosteroid therapy 0.5 mg / kg / day and received supportive treatment including plasma exchange and hemodialysis. He was discharged after a prolonged admission. At follow-up 6 months later, he had not regained kidney function and remained on hemodialysis and was still taking 3 antihypertensive treatments. A follow-up immunological workup showed a decrease in Factor I: 26,83 mg/l (32,3-87,5). The patient was diagnosed with drug-induced TMA favored by complement abnormality. Treatment with Eculizimab is under discussion. Conclusion IFN-β are main therapies for relapsing remitting multiple sclerosis. Serious complications are relatively rare and IFN-βs are generally considered to be safe. Nevertheless, rare serious and/or life-threatening side effects have been reported such as TMA. This can, as in our patient, be favored by an abnormality of the serum complement. Thus, a study on serum complement would be recommended before IFN-β prescription.

Occlusive retinal vasculopathy with macular branch retinal artery occlusion as a leading sign of atypical hemolytic uremic syndrome \u2013 a case report

BackgroundHemolytic Uremic Syndrome (HUS) is a rare disorder characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure, considered within the group of thrombocytic microangiopathies. Ocular complications in HUS are very rare. Here, we report an adult patient who suffered from acute onset of paracentral scotoma, caused by branch retinal artery occlusion (BRAO), as a leading symptom of atypical HUS.Case presentationA 39-year-old healthy male was lately diagnosed with essential hypertension and mild renal impairment. He complained about acute onset of central scotoma in his left eye. Fundus examination revealed marked narrowing of retinal vessels, cotton wool spots and few retinal hemorrhages in both eyes. The patient was diagnosed with bilateral ischemic retinal vasculopathy and acute macular BRAO in his left eye. Workup revealed thrombocytopenia, worsening renal failure. Renal biopsy showed signs of chronic thrombotic microangiopathy. The patient was diagnosed with atypical HUS (aHUS) and started on plasmapheresis, together with eculizumab. As his condition continued to worsen, he was put on renal replacement therapy. Due to a persistent monoclone of IgG1, the patient underwent bone marrow biopsy which revealed Monoclonal Gammopathy of renal significance, triggering a HUS and treatment was initiated accordingly. Two months after initial presentation, the patient developed neovascularization of the optic disc (NVD) in his left eye, and was treated with 3 monthly intravitreal bevacizumab injections with complete regression of the NVD. The patient suffered from myocardial infarction in the later course and was lost for follow-up. He returned 11 months after the last bevacizumab injection because of sudden loss of vision in his left eye caused by a dense vitreous hemorrhage. Biomicroscopy revealed a new NVD in his right eye. The patient underwent panretinal photocoagulation in both eyes with regression of neovascularization. Vision improved and remained 20/20 in both eyes.ConclusionWe present a case report showing retinal ischemia can be linked with aHUS. As clinal diagnosis might be challenging, physicians should be aware of the rare ocular manifestations of this devastating multi-organ disease. In case of retinal ischemia, panretinal photocoagulation should be initiated soon to avoid blinding complications.

Ocular ischemic changes in thrombotic microangiopathy associated with malignant arterial hypertension (case study)

The article presents a clinical observation of visual organ damage as an extrarenal manifestation of thrombotic microangiopathy in malignant arterial hypertension with an analysis of structural and functional changes in the eye by modern examination methods. The presence of renal thrombotic microangiopathy was verified by kidney biopsy. Optical coherence tomography was used to determine structural changes in the inner and outer layers of the retina in the form of their disorganization, areas of thickening of the nerve fiber layer, intraretinal inclusions and cysts, alterations of the ellipsoid zone and retinal pigment epithelium. Optical coherence tomography angiography revealed areas of vascular pattern attenuation in the deep and superficial retinal plexuses corresponding to OCT-detected foci of disorganization of the inner retinal layers. Color Doppler imaging showed absence of the diastolic component of the Doppler spectrum with an increase in the peripheral resistance index RI up to 1.0 in the central retinal artery and posterior short ciliary arteries in both eyes. Functional changes observed with multifocal electroretinography and microperimetry corresponded to the structural changes. Taking into account the similarity of microcirculation in the kidneys and the eyes, the probable pathogenetic mechanism underlying the detected structural and functional symptoms of ischemic damage to the visual organ in malignant arterial hypertension is chronic thrombotic microangiopathy. An interdisciplinary approach to studying thrombotic microangiopathy, including those associated with malignant arterial hypertension, using high-tech examination methods can be useful for timely diagnosis and treatment of this pathology.

Alternative complement pathway activation in thrombotic microangiopathy associated with lupus nephritis.

Thrombotic microangiopathy (TMA) in systemic lupus erythematosus is a rare manifestation associated with activation of the complement system. This study aimed to compare plasma and urine complement activation products between patients with active lupus nephritis (aLN) and those with acute TMA plus concomitant active LN (aTMA+aLN). Plasma and urine samples were obtained from 20 patients with aTMA+aLN, 20 patients with aLN matched by the histological activity index, 5 patients with chronic TMA, 20 patients with inactive LN, and 10 kidney donors. Complement fragments C3a, C4a, C4d, Ba, C5a, C5bC9, and factor H were determined by ELISA; and kidney C4d deposition was detected by immunohistochemistry. Patients were followed for > 12 months and complement activation products re-measured after treatment in 10 aTMA+aLN patients. Both aTMA+aLN and aLN groups had increased circulating C3a, Ba, and C5bC9; and decreased circulating C3, C4, C4a, C4d, and factor H. Urinary C3a, C5a, Ba, and C5bC9 were higher in patients with aTMA+aLN than in aLN. After treatment, levels of circulating C3, C4, and factor H increased; while levels of urinary C3a, C5a, Ba, and C5bC9 decreased in patients with aTMA+aLN. These changes were observed at each aTMA episode in two patients studied during repeated TMA episodes. There was no difference in C4d deposition in glomerular capillaries, tubular basement membrane, peritubular capillaries, and arterioles between patients with aLN and those aTMA+aLN. Circulating and urine complement activation products suggest that thrombotic microangiopathy associated with LN is mediated through activation of the alternative complement pathway. Key Points • Immune-complex kidney disease in systemic lupus erythematosus (SLE) is associated with activation of the classical, lectin, and alternative complement pathways • Indirect evidence from measurement of circulating and urinary complement pathway activation products suggests that renal acute thrombotic microangiopathy in SLE is mediated by activation of the alternative complement pathway • C4d kidney immunohistochemistry may be positive in both immune complex nephritis and thrombotic microangiopathy. Therefore, it is not a specific marker of renal thrombotic microangiopathy in SLE.

P0082CHARACTERISTICS OF ADULT PATIENTS WITH ATYPICAL HEMOLYTIC UREMIC SYNDROME IN RUSSIA

Abstract Background and Aims Atypical hemolytic uremic syndrome (aHUS) is complement mediated thrombotic microangiopathy (TMA), caused by genetic abnormalities in the complement gene cluster. Information about the course of aHUS in the adult population in Russia is not enough accumulated. This study presents the characteristics of Russian adult patients (pts) with aHUS. Aim To assess the characteristics of adult pts with aHUS in Russia. Method statistical analysis of retrospective and prospective data The study included 243 pts with acute TMA (microangiopathic hemolytic anemia, thrombocytopenia, decreased haptoglobin and / or blood schizocytosis, kidney damage) from different regions of Russia. All patients were tested for ADAMTS-13 activity, and there were no accidents of TTP in our study. Cases of acute TMA associated with pregnancy and childbirth (n=134), systemic diseases (n=10), anticancer drugs treatment (n=1) and sepsis (n=13) were excluded. 85 pts with diagnosis of aHUS were selected for further analysis. Results Characteristics of pts are presented in table 1. The average age at the time of acute episode was 32.4 years, the disease was equally common among men and women. Relapsing course was rare (n=11, 13%), the maximum number of relapses – 5. In the debut, 67.8% of pts had signs of kidney damage, in 21% - gastrointestinal tract, 4.8% - CNS, 4.8% - pulmonary thromboembolism, 1.6% - visual impairment. During the acute episode, extrarenal manifestations were detected in 70% of pts, while in 38 cases (44.7%), multiple organ failure (MOF) developed with simultaneous damage from 3 to 7 organs. The most commonly observed symptoms of gastrointestinal lesions (n = 39, 45%), CNS (n = 32, 37%), heart (n = 18, 21%), less often - the organ of vision (n = 10, 12%). Kidney damage was characterized by the development of AKI in 70%, in the rest - urinary syndrome, arterial hypertension, the initial signs of renal dysfunction in various combinations. A morphological examination of kidney was performed in 40 pts (kidney biopsy - 35, autopsy - 5): acute TMA was detected in 28 pts (70%), chronic TMA - in 7 (17.5%), a combination of acute and chronic TMA - in 2 (5%), a combination of IgA-nephropathy and TMA - in 1 case (2.5%) and in 2 patients a membrane-proliferative glomerulonephritis pattern with TMA. Genetic analysis was performed in 19 pts (22%), in 7 of which (37%) identified gene variants associated with the development of aHUS (C3 in 3 pts, CFHR5 in 2 pts, CFH in 2, in 1 case - MCP and in 1-DGKE). In addition, variants of genes of the complement system with an unclear clinical value were found in all pts (n = 19). 72% of pts (n = 61) needed renal replacement therapy, almost all pts received plasma therapy (83%) and anticoagulants (85%). Only 13 pts (15%) received complement-blocking therapy with eculizumab. In the outcome of the acute episode in 12 cases (14%) renal function fully recovered, in 20 pts (23%) signs of renal dysfunction persisted (CKD 2–4 stages), 53 pts (62.3%) reached ESRD, 10 pts died (12%). Conclusion The features of aHUS in our cohort were: 1. Severe course with the development of MOF in 45% of cases 2. High frequency of ESRD in the outcome of aHUS (62.3%) 3. The incidence of genetic mutations (37%) is comparable to foreign cohorts

P0137FIRST RUSSIAN BOSIMILAR OF ECULIZUMAB IN THE TREATMENT OF AN ADULT PATIENT WITH ATYPICAL HEMOLYTIC UREMIC SYNDROME

Abstract Background and Aims The disease diagnostics results and the efficacy of pathogenetic treatment when transferring from the original drug to the biosimilar were evaluated during clinical observation of an adult patient with aHUS. Method A 46-year-old patient has a history of hypertension since 2012 and maximum ABP of 230/130 mmHg. In 2016, newly diagnosed azotemia was identified (blood creatinine — 140 μmol/L, GFR by EPI — 54 mL/min/1.73m2). In 2018, the patient suffered an acute cerebrovascular accident in the vertebrobasilar area. On admission to Almazov National Medical Research Centre, blood test showed: creatinine – 260 μmol/L (GFR by EPI — 28 mL/min/1.73m2), urea – 11.52 mmol/L, LDH – 130 U/L, complement system C3 – 1.32 g/L, С4 – 0.37 g/L, hemoglobin – 144 g/L, platelets – 302*109/L; urinalysis showed: daily protein loss – 2.6 g/day, RBC – 0–1 per field. Taking into account the kidney damage, the renal fine-needle aspiration biopsy was performed, revealing histopathological findings typical of chronic thrombotic microangiopathy of extreme severity, arteriolar arteriosclerosis with total or subtotal luminal occlusion, extensive secondary perihilar segmental glomerulosclerosis (27%); and global glomerulosclerosis (55%). According to the study results, the secondary genesis of TMA was ruled out, as well as STEC-HUS and thrombotic thrombocytopenic purpura (TTP), systemic diseases (systemic lupus erythematosus, antiphospholipid syndrome (APS), scleroderma), malignancies, HIV infection, sepsis, malignant arterial hypertension, adverse drug events, or disseminated intravascular coagulation (DIC). Plasma ADAMTS-13 levels were also assessed. Its activity was 64% (normal range 93–113%) of ADAMTS-13 activity in the control plasma, thus the diagnosis of thrombocytopenic purpura was ruled out. Due to the absence of anti-CFH-antibodies the antibody origin of aHUS was also ruled out. To assess the contribution of additional factors promoting the development of TMA, the polymorphism of hemostasis genes was studied to reveal homozygous genotypes of platelet collagen receptors (ITGA2: 807 С/Е), heterozygous genotypes of fibrinogen genes (FGB: 455 G/А), folate cycle enzymes (methylenetetrahydrofolate reductase (MTHFR: 677 C/T), methionine synthase (MTR: 2756 A/G (D919G)), responsible for a pronounced tendency towards hyperhomocysteinemia. In the clinical case the diagnosis of aHUS was obvious, which was supported by the classical symptom cluster of TMA and histopathological verification in the absence of data suggestive of other pathological conditions. The peculiarity of this clinical case is the late diagnosis, long-standing course, and severity (complications such as an acute cerebrovascular accident in the vertebrobasilar area, target lesions, kidneys in particular). Results Taking into account the primary diagnosis, treatment with a standard dose of eculizumab was initiated. After three months of treatment the patient was transferred to therapy with Russian biosimilar of eculizumab. After the switch from the original drug, the therapy with eculizumab biosimilar continued to be associated with a positive trend including a gradual decline in azotemia level (blood creatinine – 115 μmol/L (GFR by EPI – 52 mL/min/1.73m2), blood urea – 7.10 mmol/L), proteinuria (daily protein loss – 0.6 g/day). The comprehensive treatment including antihypertensive therapy also led to the normalisation of ABP values. No adverse events associated with the therapy were noted. Conclusion The obtained results demonstrate high efficacy and safety of eculizumab biosimilar in the treatment of the adult patient with aHUS.

MON-224 DIAGNOSING RENAL THROMBOTIC MICROANGIOPATHY BASED ON HISTOPATHOLOGY IN RAPIDLY PROGRESSIVE RENAL FAILURE

Appart from glomerular and tubulointerstitial lesion of rapidly progressive renal failure (RPRF), renal vascular lesion is a critical prognostic finding in which renal thrombotic microangiopathy (TMA) present with severe clinical manifestation and have a high morality. The aim of this study were to describe (1) the histopatological features of TMA, (2) its classification and (3) the associated lesions in RPRF. We observed 133 kidney biopsies performed in patients presented with RPRF from 2013 to March 2018 by by using light microscopy. Renal TMA was classified as acute TMA, defined by luminal thrombi including fibrin and fragments of red blood cells and associated with ischemic capillaries, mesangiolysis and edematous and mucinous intimal thickening, often infiltrated with foam cells. Chronic TMA was characterized by onion-skin fibrointimal sclerosis. Chronic active TMA showed both acute and chronic changes. There were 38 cases of TMA diagnosed histopathologically including 31/38 (81.6%) lupus nephritis (LN) with 26/31 classIV, 1/31 class V, 1/31 class III-V, 2/31class IV-V; 6/38 (15.8%) IgA nephropathy (IgAN) and 1/38 (2.6%) focal segmental sclerosis (FSGS). All 45% acute TMA were LN. 23% chronic TMA included 13% LN, 8% IgAN and 2% FSGS. 32% Chronic active TMA were 24% LN and 8% IgAN. Only one LN (2.6%) showed thrombus in artery. 34.2% cases with capillary occlusion were LN. The associated arteriolar lesions including thrombi (55.3%), edematous and mucinous intimal thickening (73.7%), fibrointimal sclerosis (34.2%) and immunofluorescence staining of thrombi with fibrin (44.7%) presented both in LN and IgAN. 55% had ischemic glomeruli. The FSGS solely showed arteriolar fibrointimal sclerosis and ischemic loops suggested for chronic TMA. The mesangiolysis, endothelial swelling and subendothelial expansion were not recognised in our observation probably due to the limitation of the quality of the microscopic slides as well as the lack of electromicroscopic equipment. The duplication of the basement membrane features was not applied for defining chronic TMA in capillaries especially in LN because of its frequent presence in many chronic conditions. Pathological features of renal thrombotic microangiopathy can varies considerably and can be seen frequently in many different severe kidney conditions.

SUN-168 OUTCOMES OF ACUTE KIDNEY INJURY FOLLOWING HEMOTOXIC SNAKE ENVENOMATION

Snake envenomation is a common cause of acute kidney injury in the tropics. There is only limited data on predictors of mortality and long-term outcomes of snake bite related AKI. The current study aims to identify the predictors of mortality in patients with snake bite AKI. The study also aims to assess the long-term outcomes (GFR <60 ml, urine albumin excretion > 30, presence of hypertension/prehypertension) in patients who recover from snake bite AKI. All adult patients admitted with features of systemic haem toxicity and AKI from January 2016 to June 2017, were recruited for the study . AKI was defined according to KDIGO criteria . Patients with history history of CKD were excluded . Demographic, clinical and laboratory details were collected during hospital admission. A first follow up visit was scheduled 2 weeks after discharge from the hospital. All patients were called for the final follow up visit in June 2018. Among a total number of 420 patients with hemotoxic snake bites , 214 (50.9 %) had features of systemic hemotoxicity . 184 patients (43.8 %) satisfied the KDIGO criteria for AKI( stage 1= 14 (07.6 %),stage 2- 35(19%),stage 3- 115(62.5%). KDIGO urine output as well as creatinine criteria was met in 106 (57.6%) patients . 45(24.5%) patients met only the creatinine criteria and 33 (17.9%) met only urine output criteria. The comorbidities present in the population were systemic hypertension (n=7) and diabetes mellitus (n=2). The mortality rate for patients with hemotoxic envenomation was 21.1% (n = 46 /214). The mortality was considerably higher in patients with stage 3 AKI ( RR- 5.05 ; 95% CI 1.28 -19.85) as well as those who met both urine output and creatinine criteria (RR- 3 .02; 95% CI 2.01-4.53). On cox regression analysis, the independent predictors of mortality were presence of capillary leak syndrome (RR- 2.02; 95% CI 1.05-3.88), mechanical ventilation (RR- 5.59; 95% CI 2.90 -10.81) and hypotension (RR- 2.48; 95% CI h1.31-4.72). Among the survivors (n=140), at the time of discharge, 44 patients (31.4%) had a complete recovery of kidney function . At 2 weeks post discharge, 23 patients had e GFR values < 60 ml/1.73 m 2 (32.3%). Long term follows up data was available for 53 patients. The median follows up duration was 20 months (IQR 6-24.5). The mean eGFR at the end of follow up was 85.62 ml /1.73 m2 (95% CI 79.1,92.2). A total of 12/53(22.6%) patients developed adverse renal outcomes at the end of follow up . Among these . 08 patients (15%) patients developed CKD, 3 patients developed prehypertension and one patient had new onset hypertension. Kidney biopsy was done in three patients, chronic thrombotic microangiopathy was documented in 2 patients and one patient showed persistent acute tubular necrosis Higher stages of AKI,mechanical ventilation,hypotension and capillary leak were associated with a higher risk of mortality in snake bite related AKI. One fifth of patients who sustain AKI following snake envenomation develop adverse renal outcomes on follow up.

Diacylglycerol kinase epsilon nephropathy: late diagnosis and therapeutic implications.

A 17-year-old male presented thrombotic microangiopathy (TMA) at 6 months of age with arterial hypertension, anemia, thrombocytopenia and kidney injury improving with plasma infusions. Fourteen years later, he was diagnosed with severe arterial hypertension, increase in serum creatinine and chronic TMA on kidney biopsy. Eculizumab was started and after 18 months of treatment, he persisted with hypertension, decline in renal function and proteinuria. Genetic analysis demonstrated mutation in diacylglycerol kinase epsilon (DGKe). Complement blockade was stopped. This case of late diagnosis of DGKe nephropathy highlights the importance of genetic testing in patients presenting TMA during the first year of life.

Bevacizumab-associated glomerular microangiopathy

Bevacizumab is a humanized monoclonal IgG1 antibody, which neutralizes vascular endothelial growth factor and is used for treating multiple cancer types. As a known and frequent adverse event, this therapy can lead to renal damage including proteinuria and nephrotic syndrome. In a retrospective approach, we analyzed 17 renal biopsies from patients receiving bevacizumab treatment. We observed a distinctive histopathological pseudothrombotic pattern different from the previously reported thrombotic microangiopathy. Since this pattern includes some features similar to acute and chronic thrombotic microangiopathy, focal segmental glomerulosclerosis and cryoglobulinemic membranoproliferative glomerulonephritis, biopsies with these diagnoses were included for comparison. Clinical, laboratory, light microscopic, immunohistochemical (including a proximity ligation assay), proteomic and electron microscopic features were assessed. Nephrotic syndrome was present in 15 of the 17 bevacizumab-treated patients. All 17 displayed a patchy pattern of variably PAS-positive hyaline pseudothrombi occluding markedly dilated glomerular capillaries in their biopsies. Mass spectrometry-based proteome analysis revealed a special protein pattern demonstrating some features of thrombotic microangiopathy and some of cryoglobulinemic glomerulonephritis, including a strong accumulation of IgG in the pseudothrombi. Proximity ligation assay did not show interaction of IgG with C1q, arguing for accumulation without classic pathway complement activation. In contrast to thrombi in thrombotic microangiopathy cases, the hyaline pseudothrombi did not contain clusters of CD61-positive platelets. Electron microscopy of bevacizumab cases did not show fibrin polymers or extensive loss of podocyte foot processes. Even though cases of bevacizumab-associated microangiopathy share some features with thrombotic microangiopathy, its overall histopathological pattern is quite different from acute or chronic thrombotic microangiopathy cases. We conclude that bevacizumab therapy can lead to a unique hyaline occlusive glomerular microangiopathy, likely arising from endothelial leakage followed by subendothelial accumulation of serum proteins. It can be diagnosed by light microscopy and is an important differential diagnosis in cancer patients with nephrotic syndrome.

Hyperfunctional complement C3 promotes C5-dependent atypical hemolytic uremic syndrome in mice

Atypical hemolytic uremic syndrome (aHUS) is frequently associated in humans with loss-of-function mutations in complement-regulating proteins or gain-of-function mutations in complement-activating proteins. Thus, aHUS provides an archetypal complement-mediated disease with which to model new therapeutic strategies and treatments. Herein, we show that, when transferred to mice, an aHUS-associated gain-of-function change (D1115N) to the complement-activation protein C3 results in aHUS. Homozygous C3 p.D1115N (C3KI) mice developed spontaneous chronic thrombotic microangiopathy together with hematuria, thrombocytopenia, elevated creatinine, and evidence of hemolysis. Mice with active disease had reduced plasma C3 with C3 fragment and C9 deposition within the kidney. Therapeutic blockade or genetic deletion of C5, a protein downstream of C3 in the complement cascade, protected homozygous C3KI mice from thrombotic microangiopathy and aHUS. Thus, our data provide in vivo modeling evidence that gain-of-function changes in complement C3 drive aHUS. They also show that long-term C5 deficiency is not accompanied by development of other renal complications (such as C3 glomerulopathy) despite sustained dysregulation of C3. Our results suggest that this preclinical model will allow testing of novel complement inhibitors with the aim of developing precisely targeted therapeutics that could have application in many complement-mediated diseases.

MULTI-ORGAN DYSFUNCTION, PANCYTOPENIA, AND ELEVATED INFLAMMATORY MARKERS DURING NEUROBLASTOMA THERAPY

Introduction Thrombotic microangiopathy (TMA) and hemophagocytic lymphohistiocytosis (HLH) have overlapping features, including multi-organ dysfunction and cytopenias. Herein we present the challenging case of a 13-year old boy with manifestations of both TMA and HLH, whose diagnosis was not clarified until weeks into the course with renal-biopsy electron microscopy (EM). Case Description The patient is a 13 year-old male with stage 4 neuroblastoma, status-post 6 cycles of chemotherapy (cisplatin/etoposide/vincristine/cyclophosphamide /doxorubicin/carboplatin/topotecan), two tandem stem cell transplants (with thiotepa/cyclophosphamide/carboplatin/etoposide/melphalan) followed by dinutuximab and isotretinoin. During his first cycle of consolidation therapy with Hu-3f8, he developed transverse myelitis, followed by heart failure. In his subsequent 6-week admission, his course was complicated by hypertension and renal failure; pan-cytopenia (hemolytic anemia, thrombocytopenia, lymphopenia) with intermittently positive Coombs; diffuse alveolar hemorrhage; and transaminitis with direct hyperbilirubinemia. He was diagnosed with and treated for Legionella pneumonia 12 days into this course; additional comprehensive infectious workup was unrevealing. He had persistently elevated ferritin (10,000 to 30,000 ng/mL), procalcitonin, CRP and triglycerides. Renal biopsy immunohistochemistry showed diffuse acute tubular injury, without immune complex-mediated glomerular lesions. C5b9 and ADAMTS13 were normal. Soluble IL-25 was elevated (2388 ng/mL). Bone marrow biopsy showed occasional hemophagocytes. Renal-biopsy EM eventually showed microangiopathic changes consistent with chronic TMA. Discussion Chronic drug-induced, toxicity-mediated TMA may present with features of HLH and TMA. As symptoms may manifest weeks to months after drug administration, the inciting agent may be difficult to identify. Without a specific biomarker, the diagnosis may not be apparent without renal-biopsy EM.

Characteristic morphological changes in anti-VEGF therapy-induced glomerular microangiopathy.

Agents targeting vascular endothelial growth factor (VEGF) have increasingly been used for the treatment of advanced malignancies, and have been found to induce renal thrombotic microangiopathy (TMA) and proteinuria. However, histomorphological changes in human biopsies in this setting and the underlying mechanism are not yet fully understood. Therefore, we collected renal biopsy cases with a history of aVEGF therapy to review and compare morphological kidney changes in this context. Renal biopsies of 15 patients who had received anti-VEGF (aVEGF) therapy evaluated between 2013 and 2017 at a single centre were morphologically characterised with light microscopy, electron microscopy, and immunohistochemistry (IgA, IgG, IgM, C1q, and C3), and compared with cases with acute TMA caused by atypical haemolytic-uraemic syndrome or hypertension. Morphological overlap with immune complex and cryoglobulinaemic membranoproliferative glomerulonephritis, diabetic glomerulopathy and pre-eclampsia-induced glomerulopathy are discussed. Segmental glomerular capillary microaneurysms and segmental hyalinosis were typical morphological features of aVEGF therapy-induced glomerular microangiopathy, whereas fibrin or platelet thrombi or fragmented erythrocytes were rarely found or were absent. aVEGF therapy-associated microangiopathy was diffusely distributed in the glomeruli, spared preglomerular vessels, and showed morphological characteristics of chronic TMA. In individual cases, aVEGF therapy-induced glomerular microangiopathy was accompanied by immune-complex glomerulonephritis. aVEGF therapy-induced glomerular microangiopathy has a characteristic morphology and clinical presentation that helps to differentiate it from other causes of TMA. Awareness of these light microscopic findings allows identification of aVEGF therapy as a trigger of renal disease in critically ill cancer patients, and might therefore help in deciding on further therapy.