Glomerular Involvement Research Articles

Sacituzumab-govitecan-induced severe acute tubulointerstitial nephritis requiring hemodialysis

BackgroundSacituzumab govitecan is an antibody-drug conjugate that is FDA approved for refractory metastatic triple-negative breast cancer. It targets the human trophoblastic cell-surface antigen 2 (Trop-2) with SN-38, a topoisomerase I inhibitor, attached to the antibody [1]. SN-38 breaks DNA strands and induces tumor apoptosis [2]. Acute kidney injury (AKI) is one of its adverse effects mainly prerenal due to gastrointestinal toxicity, but it has not been reported to cause acute tubulointerstitial nephritis (ATIN).Case PresentationThis report describes a rare adverse effect of sacituzumab govitecan, the approach to diagnosing the etiology of the patient’s AKI, and the mechanism by which sacituzumab govitecan causes ATIN. A woman with metastatic ER positive, PR positive, HER2 negative breast cancer who was initiated on sacituzumab govitecan presents with vomiting and diarrhea, and findings of nephrotic-range proteinuria, negative anti-PLA2R antibody, and severe AKI requiring hemodialysis. She underwent kidney biopsy and pathology showed ATIN characterized by patchy interstitial inflammation alongside tubular injury without glomerular and vascular involvement. With intermittent renal replacement therapy, furosemide challenge, and a course of prednisone, the patient’s kidney function recovered.ConclusionsSacituzumab has a high affinity for Trop-2 protein which is also expressed within the collecting ducts, and to a lesser extent, the proximal tubule. Individuals, such as this patient, who express a homozygous genotype for UGT1A1*28 allele are at increased risk for AKI from sacituzumab govitecan due to decreased glucuronidation of SN-38.

Kidney involvement in myelodysplastic syndromes.

The objective of this study was to describe kidney involvement in patients with myelodysplastic syndromes (MDS), their treatments, and outcomes. We conducted a multicenter retrospective study in seven centers, identifying MDS patients with acute kidney injury (AKI), chronic kidney disease (CKD), and urine abnormalities. Fifteen patients developed a kidney disease 3 months after MDS diagnosis. Median urine protein-to-creatinine ratio was 1.9g/g, and median serum creatinine was 3.2mg/dL. Ten patients had AKI at presentation, and 12 had extra-renal symptoms. The renal diagnoses included anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), ANCA negative vasculitis, C3 glomerulonephritis, immune complex-mediated glomerulonephritis, polyarteritis nodosa, and IgA vasculitis. All patients but one received a specific treatment for the MDS-associated kidney injury. The effect of MDS treatment on kidney injury could be assessed in six patients treated with azacitidine, and renal function evolution was heterogenous. After a median follow-up of 14 months, four patients had CKD stage 3, five had CKD stage 4, and three had end stage kidney disease. On the other hand, three evolved to an acute myeloid leukemia and three died. Compared to 84 MDS controls, patients who had kidney involvement were younger, had a higher number of dysplasia lineages, and were more eligible to receive hypomethylating agents, but no survival difference was seen between the two groups. Compared to 265 AAV without MDS, the ten with MDS-associated pauci-immune vasculitis were older, ANCA serology was more frequently negative, and more cutaneous lesions were seen. The spectrum of kidney injuries associated with MDS is mostly represented by vasculitis with glomerular involvement, and especially AAV.

#2724 Renal amyloidosis cohort registry in our health area

Abstract Background and Aims Renal amyloidosis is the pathological phenomenon of amyloid deposition in the kidney with marked differences in renal function impairment, proteinuria, need for renal replacement therapy (RRT) and exitus, depending on the protein involved. Light chain amyloidosis (AL) and serum protein A (AA) amyloidosis are the most common. Typical symptoms are severe proteinuria, nephrotic syndrome, and end-stage chronic kidney disease (ESRD). Method Retrospective study of a cohort of patients with renal amyloidosis. Data extracted from the biopsy registry of the HUVM Nephrology Service (2013-2022). We collected demographic, clinical, analytical, histological and clinical outcome variables (RTT, Exitus). Results are analyzed using Mayo Clinic staging criteria. Results 19 patients with a mean age of 63.4a; 57.9% male. Mean laboratory values at diagnosis: creatinine (Cr) 1.56 mg/dl and proteinuria 3.9 g/24 h. Abdominal fat biopsy in 13 cases; 3 (23%) tested positive. Comparative analysis of AL vs non-AL forms, Cr values (1.14 vs 2.27 mg/dl respectively) (p=0.57) differed. Proteinuria according to the histological location of the amyloid: 4.6 g/24 h in glomerular involvement vs. 0.3 g/24 h in those who did not present it (p<0.05). 31.6% required RTT with a mean onset time of 250.6 d from biopsy. Exitus of 21.1%: average time of 426.5 d. (See analysis in attached table). Conclusion We did not observe significant deterioration of renal function, which is greater in non-AL forms of amyloidosis. Fat biopsy was less cost-effective than reported in the literature. Significantly lower levels of proteinuria were found in the amyloidosis group without glomerular involvement. In our series, the prognostic capacity associated with the MAYO staging was confirmed.

#1121 Identification of kidney transcripts associated with prognosis in ANCA-associated glomerulonephritis

Abstract Background and Aims Kidney involvement in ANCA-associated vasculitis (AAV-GN) predicts poor patient and kidney survival. Deciphering the transcriptomic landscape in AAV-GN may provide insights into pathogenic mechanisms or identify biomarkers for refining diagnosis and/or prognosis, which would help stratify risk and tailor therapeutic management. We aimed to investigate the potential prognostic value of kidney transcripts associated with kidney survival. Method This study included adult patients with AAV-GN from the French Maine-Anjou Registry. Immune gene transcript analysis was performed on RNA extracted from 97 AAV-GN kidney biopsies using NanoString technology. Transcripts of interest were selected, and their prognostic performance was assessed with respect to current histological-based classifications. Following the identification of a possible role for clusterin (CLU), the relationship between serum CLU and prognosis was assessed. Results Among the 750 evaluated transcripts, we identified a 4-gene signature (XRCC6, PRKCD, TEK, and CLU) that was strongly associated with kidney survival (Fig. 1A). This signature predicted kidney survival better than histological-based classifications (global C-Index 0.87 vs. 0.65 for Berden classification or 0.81 for Renal Risk Score, with better time-dependent AUC and Brier scores, especially beyond 1 year after diagnosis) (Fig. 1B). Among these 4 transcripts, the expression level of the CLU transcript had the highest correlation with glomerular involvement, kidney function at diagnosis, and kidney survival. Serum CLU levels were associated with kidney survival, especially when assessed at 6 months from diagnosis (Fig. 1C, P = .023). Conclusion Transcriptomic analysis of kidney biopsies of AAV-GN identified potential transcripts that may improve prediction of kidney survival. This transcriptomic signature may help us gain a deeper understanding of the AAV-GN pathogenesis and provide insights for developing new therapeutic options.

#2699 Rare glomerular microangiopathy: clinicopathological characteristics and prognosis

Abstract Background and Aims Different from the typical histologic changes of thrombotic microangiopathy (TMA), we identified a group of patients whose pathology with glomerular involvement without blood vessel lesions, which was rare and known as glomerular microangiopathy (GMA). Method In Peking Union Medical College Hospital, a total of 33 patients were diagnosed as GMA with proliferation and swelling of glomerular endothelial cells, fragmented red blood cells, fibrin or platelet thrombi in the capillary lumen, thickening of the basement membrane, stenosis or occlusion of capillary lumen, but no abnormalities in the endothelium of renal small vessels. The pathology and clinical data were from the medical records and analyzed. Results The patients were 66.7% male with a mean of 45 years (14 to 74 years). The primary diseases were Castleman's disease (CD, 30.3%), POEMS syndrome (21.2%), cancer patients receiving agents targeting vascular endothelial growth factor (21.2%), and others. All the patients showed various degrees of proteinuria, with an average 24-hour urinary protein of 2.66 g/d, hematuria (63.6%), and acute kidney injury (AKI, 39.4%). The median serum creatinine (SCr) was 142 (107.5, 169) μmol/L. The AKI patients had lower Alb (P < 0.0001), PLT (P = 0.0192), higher high-sensitivity C-reactive protein (hs-CRP) (P = 0.0199), and reduction of IgA (P = 0.0021). There is no significant difference in SCr and proteinuria among patients with different etiologies. The CD patients exhibited higher hs-CRP and D-Dimer. Treatment included targeting therapy of underlying hematological disorders, glucocorticoid combination with or without immunosuppressant, and supportive treatment. After treatment, we observed proteinuria remission (66.7%), partial improvement (27.3%), or complete recovery (45.5%) of renal function. Conclusion In Castleman's disease, POEMS syndrome, and patients receiving agents targeting VEGF, initial attention to GMA might improve the prognosis and shed light on the study of the mechanisms.

#3087 Phenotype of extracellular vesicles in diabetic kidney disease with albuminuria

Abstract Background and Aims Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) and affects more than 40% of patients with type 2 diabetes mellitus (T2D). The pathogenesis of CKD is multifactorial and leads to a clinical presentation with diverse phenotypes characterised by proteinuria and/or progressive deterioration of renal function, thus urging the search for new non-invasive biomarkers that allow early diagnosis and the development of new therapeutic targets. Urinary extracellular vesicles (EVs) have emerged as an alternative, as changes in their number and composition have been described in clinical conditions associated with DM and kidney disease. EVs are able to interact with neighbouring and/or distant cells by transferring their cargo, rich in proteins, lipids or nucleic acids, from progenitor cells to recipient cells, thus participating in cell-to-cell communication processes. The aim of the present study was to analyse the different phenotypes of EVs in T2D patients with different degrees of albuminuria compared to healthy controls, as well as their correlation with the degree of albuminuria. Method A cohort of 69 subjects (49 patients with T2DM and 20 healthy volunteers) was analysed. The phenotype of EVu present between the two groups was assessed, as well as the association between the different cell lines and the presence of albuminuria. Statistical analysis was performed using Spearman correlations. Analyses were performed with R software. Results A positive correlation was observed between EVu from podocytes (PODO+) and those from macrophagocytes (R = 0.3180, p-value = 0.0082), as well as a positive association between PODO+ and neutrophil EVu, both in the whole cohort and when analysing only patients with diabetes (R = 0.3225, p-value:0.0254). When assessing the association of EVu with the degree of albuminuria, we observed a direct association with proximal tubule EVu (R: 0.3158, p-value 0.0271) both in all subjects (T2D and HV) and only in those with T2D (R = 0.4200, p-value = 0.0056). When stratifying according to the degree of albuminuria (A1, A2 and A3), we still observed a dependent association of the degree of glomerular involvement with the number of EVu of TCP (A1: mean 5.5 (SD 4.1); A2: mean 12.3 (SD 30.9); A3: mean 132.5 (SD 322.8)) p-value: 0.0609. Conclusion The results presented suggest a relevant role of TCP in the glomerular involvement of patients with DKD, in line with the emergence of new therapeutic lines such as iSGLT2. The study suggests new lines of research aimed at developing therapeutic targets that assess the cellular expression of EVu.

#1150 Neutrophil rich infiltrate in immunotherapy induced acute interstitial nephritis

Abstract Background and Aims Acute interstitial nephritis (AIN) is a well-recognized cause of acute kidney injury (AKI) in patients treated with Immune checkpoint inhibitors (ICI). Kidney biopsy typically shows tubular interstitial infiltration with well-differentiated mononuclear cells with occasional granulomas and eosinophils. Neutrophil rich tubular interstitial infiltration is typically associated with pyelonephritis. We report a case series of neutrophil rich ICI induced AIN. Method After obtaining approval from the institutional review board, medical records of the nephrology service at a large cancer center were reviewed. Patients were included in the study if they underwent a kidney biopsy for the diagnosis of ICI associated AKI, the biopsy was consistent with atypical AIN with neutrophil rich infiltrate, there was no glomerular involvement, they exhibited no symptoms of pyelonephritis including but not limited to fever, nausea, vomiting, flank pain and dysuria and had a negative urine culture. Results Forty eight patients who had a biopsy proven ICI associated AIN were identified from the medical records. Four (8.3%) patients met the study criteria (Table 1). There were three males and one female. The mean age was 75.5 years. One patient had a history of pre-existing CKD stage 3. Mean number of ICI therapy cycles prior to the development of AIN was seven with two patients treated with pembrolizumab (2 and 14 cycles), one patient treated with nivolumab (1 cycle) and one patient treated with the combination of nivolumab and ipilimumab (2 cycles). All patients presented with asymptomatic rise in serum creatinine (sCr). Kidney biopsy showed neutrophil rich infiltrate and neutrophilic tubulitis in all patients. Neutrophilic casts were present in three biopsies. One patient had evidence of granulomatous inflammation. All patients had mild to moderate interstitial fibrosis. Three patients were initially treated with flat dose prednisone 60 mg daily and one was treated with weight adjusted dose of prednisone 1 mg/kg at 75 mg/day. Three patients had complete renal recovery (sCr < 0.5 mg/dl above baseline) after steroid taper. One patient developed a relapse but achieved partial recovery (sCr < 2x baseline) after the second taper. Two patients remain alive three and 12 months after the kidney biopsy. Two patients died due to the progression of cancer two and 10 months after the biopsy. Conclusion AIN with neutrophil rich infiltrate likely represents a subset of ICI induced AIN. In the absence of clinical signs of pyelonephritis and with evidence of negative urine cultures the treatment should be geared towards addressing inflammation with systemic corticosteroids which have been shown to be effective in management of ICU induced AIN. Avoidance of antibiotics in this setting would lead to better antibiotic stewardship.

#2123 Ageing, renal function and frailty: analysis of the FRASNET study

Abstract Background and Aims Frailty is a common geriatric syndrome of significant public health importance. The kidney is one of the organs that progressively loses function with aging leading a decrease of glomerular filtration rate (GFR). In elderly the definition of eGFR threshold for the diagnosis of CKD is debated. FRASNET study aims of identify the role of kidney function (glomerular and tubular involvement) in determining frailty among not community-dwelling elderly adults, also depending on the genetics of each single subject. Method The FRASNET study was a cross-sectional multicentre observational cohort study involving healthy. The exclusion criteria were: i) severe cognitive impairment, ii) severe health problems. They have been characterised for BP, GFR, sodium intake (Kawasaki formula), cognitive status, quality of life, anamnestic factors, health and socio-economic status. Frailty was determined according to modified Fried index by the presence of three conditions among reduced grip strength, reduced gait speed, low physical activity, self-reported exhaustion. We considered the number of drugs as an index of comorbidity. Genotyping of 20 targeted single nucleotide polymorphisms (SNPs) selected on renal and hypertension was performed. ANOVA and conditional inference tree analysis have been carried out. Results 1183 individuals were included in the study sample. Median age was 72 [IQ 69-77]. 328 (27.7%) subjects were robust, 445 (37.6%) pre-frail, 410 (34.7%) frail. Frailty increases with age, especially after 75 years (from 28.9% to 75.7%). The overall mean GFR was 71.8 ± 16.5 ml/min/1.73 m2. Estimated 24 h urinary sodium excretion was 194.5 mEq/24 h with median fractional excretion of sodium (FeNa) 0.75%. In 31.9% of sample FeNa was greater than 1%. Only 3% of subjects reported CKD. Moreover, 21.1% presented eGFR ≤ 60 and the prevalence of CKD increases according to age from 12.3% to 70.3%. CKD prevalence increases in linear manner across frailty classes from 20% in robust to 47.6% in frail. Conditional inference tree analysis confirmed the role of age, comorbidity and GFR in determining frailty. In oldest subjects (>75 years old), the eGFR level most strongly associated with frailty was below 53 (ml/min/1.73 m2) (Fig. 1). No differences in sodium excretion were observed according to frailty classes. Moreover, we observed an increase of FeNa according to age and frailty classes form 0.71% (median (IQR 0.567)) to 0.79% (median (IQR 0.690)). In frail group exaggerated FeNa (>1%) is more frequent than in robust and pre-frail subjects (Chi-squared p = 0.021). Even after the introduction of these variables in inferential trees the new proposed cut-off for GFR (53) is a main determinant of frailty in oldest (Fig. 2). The eGFR parameter resulted associated with two genetic variants in RAAS system, rs5051 in the angiotensinogen gene (AGT) and rs2131127 in the angiotensin II receptor type 1 (AGTR1). The rs4293393 in uromodulin gene (UMOD) was confirmed associated with eGFR value. Conclusion The present study is part of the complex debate on the relationship among renal function, aging and frailty. We can therefore conclude that glomerular filtration (eGFR below 50 and not the presence of CKD) must be considered among the factors that influence frailty. Our study also showed a deterioration of tubular function in frail subject that can be expression of structural changes due to nephroangiosclerosis.

Autosomal dominant chronic tubulointerstitial nephropathy: do not forget amyloidosis

Amyloidosis is a rare cause of inherited kidney disease, with most variants responsible for prominent glomerular involvement. In this issue, Kmochová etal. reported the first description of autosomal dominant medullary amyloidosis due to apolipoprotein A4 variants, resulting in slowly progressive chronic kidney disease with minimal proteinuria. Combining next-generation sequencing with histopathological studies incorporating Congo red staining and mass spectrometry should be considered in the diagnostic workup of hereditary tubulointerstitial disorders not identified after routine genetic testing.

Simultaneous presentation of membranoproliferative glomerulonephritis and tuberculous spondylitis: a case report

Genitourinary tuberculosis is not uncommon. Skeletal tuberculosis with tuberculous spondylitis is also a well-known entity. However, spinal tuberculosis presenting with nephrotic syndrome due to glomerular involvement is rare. We report a patient with tuberculous spondylitis and membranoproliferative glomerulonephritis. A 40-year-old man presented with bilateral lower limb swelling of two weeks duration, a non-inflammatory type of back pain of one year duration, and constitutional symptoms. He had nephrotic range proteinuria and hypoalbuminemia, with normal renal function and normal size kidneys on ultrasound scanning. MRI spine revealed tuberculous spondylitis involving T12 and L1 vertebrae with associated para-spinal and psoas abscess formation. Renal biopsy revealed membranoproliferative glomerulonephritis. Aspirate from psoas abscesses was positive for Mycobacterium tuberculosis. The patient was treated with anti-tuberculous therapy and required spinal fixation. With treatment both proteinuria and other symptoms improved.

Cutaneous vasculitis in autoinflammatory diseases.

Autoinflammatory diseases (AIDs) characterized by recurrent episodes of localized or systemic inflammation are disorders of the innate immune system. Skin lesions are commonly found in AIDs and cutaneous vasculitis can coexist with AIDs and even present as the most striking feature. This review aims to focus on the frequent cutaneous vasculitis association in three monogenic AIDs including familial Mediterranean fever (FMF), deficiency of adenosine deaminase type 2 (DADA2), and the recently identified adult-onset VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. Cutaneous vasculitis in FMF is characterized by: (1) small-vessel vasculitis similar to IgA vasculitis with palpable purpura but increased intussusception complication and less vascular IgA deposit, and (2) cutaneous arteritis-like vasculitis presenting as subcutaneous nodules most often with higher glomerular involvement. DADA2 has a wide spectrum of clinical presentations ranging from fatal systemic vasculitis with multiple strokes, especially in pediatric patients, to limited cutaneous disease in middle-aged patients. DADA2 shares similar clinical and histopathological features with polyarteritis nodosa (PAN). As a result, DADA2 is commonly initially misdiagnosed as childhood PAN. Livedo racemosa reveals the most common cutaneous manifestation of cutaneous vasculitis in patients with DADA2. VEXAS syndrome is a life-threatening disease. A diagnosis of VEXAS syndrome should be strongly considered or could be made in patients with skin lesions characterized by Sweet syndrome-like eruption, livedo racemosa, concomitant relapsing polychondritis, deep venous thrombosis, pulmonary involvement, and progressive hematologic abnormalities such as myelodysplastic syndrome with a unique finding of cytoplasmic vacuoles in myeloid and erythroid precursor cells from bone marrow aspirate smear. As skin involvement is common in AIDs and may present as the most frequent manifestation, especially in DADA2 (70% to 90%) and VEXAS syndrome (83% to 91%), dermatologists play a crucial role in contributing to the early diagnosis of these AIDs with early initiation of the appropriate therapy to avoid progressing fatal outcomes.

The Prevalence of Microalbuinuria & Associated Risk Factors at the Time of Diagnosis among Type 2 Diabetic Patients in Rajshahi City, Bangladesh

Background: The presence of albumin in the urine is a marker of glomerular involvement in type 2 diabetes mellitus (T2DM), depicting diabetic nephropathy. Strict glycemic control can prevent and delay the occurrence of microalbuminuria and other diabetic complications. Therefore, this study evaluated the prevalence of microalbuinuria & associated risk factors at the timi e of diagnosis among type 2 diabetic patients in Rajshahi city.
 Methods: Between January 2019 and December 2019, a cross-sectional analytical study was collaboratively undertaken by the Department of Physiology at Rajshahi Medical College and the Diabetic Association Hospital in Rajshahi. Following an initial evaluation, patients underwent an oral glucose tolerance test (OGTT) for a conclusive diagnosis of DM. Subsequently, subjects were subjected to rigorous screening procedures based on specific inclusion and exclusion criteria. Study group A consisted of 80 diabetic subjects, while an equivalent number of age- and gender-matched non-diabetic individuals were recruited for study group B, with participants drawn from hospital staff, patients' relatives, and volunteers, resulting in a total of 80 participants in each group.
 Results: The study findings showed that among the healthy adult group, 85% had normal fasting blood sugar (FBS), while 15% had impaired fasting sugar (IFG). Conversely, in the diabetic group, none had normal FBS or IFG. The mean urine microalbumin level was significantly higher in the diabetic group (24.63±14.75 mg/day) compared to the control group (11.59±5.41 mg/day), indicating abnormal levels in about one-third of diabetic respondents versus none in the healthy group. Additionally, all healthy adults had normal urine spot microalbumin levels, whereas 25 diabetic respondents exceeded normal levels.
 Conclusion: Newly diagnosed diabetic patients showed higher levels of urine microalbumin compared to healthy adults, suggesting potential early markers for diabetic nephropathy. However, further large-scale prospective studies are required to confirm their clinical usefulness for routine screening.

Acyclovir-Induced Glomerulonephritis in a 40-year-old Woman Without Medical History: A Case Report.

Presentation of a case of acute kidney injury, with haematuria and proteinuria in nephrotic ranges, after acyclovir administration. These findings suggest glomerular involvement; we postulate a hypothesis of a nephritis with podocyte damage.Observation of associated mild encephalopathy in a patient without pre-existing kidney failure.Toxic mechanism of glomerular damage and combined encephalopathy. This should be further investigated.

Misdiagnosed Branchio-Oto-Renal syndrome presenting as proteinuria and renal insufficiency with insidious signs since early childhood: a report of three cases

BackgroundBranchio-oto-renal (BOR) syndrome is an inherited multi-systemic disorder. Auricular and branchial signs are highly suggestive of BOR syndrome but often develop insidiously, leading to a remarkable misdiagnosis rate. Unlike severe morphological abnormalities of kidneys, knowledge of glomerular involvement in BOR syndrome were limited.Case presentationThree cases, aged 8 ~ 9 years, visited pediatric nephrology department mainly for proteinuria and renal insufficiency, with 24-h proteinuria of 23.8 ~ 68.9 mg/kg and estimated glomerular filtration rate of 8.9 ~ 36.0 mL/min/1.73m2. Moderate-to-severe albuminuria was detected in case 1, while mixed proteinuria was detected in case 2 and 3. Insidious auricular and branchial fistulas were noticed, all developing since early childhood but being neglected previously. EYA1 variants were confirmed by genetic testing in all cases. Delay in diagnosis was 8 ~ 9 years since extra-renal appearances, and 0 ~ 6 years since renal abnormalities. In case 1, therapy of glucocorticoid and immunosuppressive agents to accompanying immune-complex mediated glomerulonephritis was unsatisfying.ConclusionsBOR syndrome is a rare cause of proteinuria and abnormal kidney function and easily missed, thus requiring more awareness. Careful medical history taking and physical examination are essential to early diagnosis. Massive proteinuria was occasionally seen in BOR syndrome, which might be related to immune complex deposits. A novel pathogenic variant (NM_000503.6 (EYA1): c.1171delT p.Ser391fs*9) was firstly reported.

Tubular basement membrane deposits after allogeneic hematopoietic stem cell transplantation

BackgroundExtraglomerular immune complex deposition is rare and only a few membranous nephropathy cases with tubular basement membrane deposits have been reported following allogeneic hematopoietic stem cell transplantation.Case presentationWe reported a 56-year-old man with increased serum creatinine after allogeneic hematopoietic stem cell transplantation who underwent a renal biopsy. Tubular interstitial nephritis was identified on light microscope. The unique histologic features were diffuse tubular basement membrane immune complex deposition detected by both immunofluorescence and electron microscopy, while the glomerular involvement was inconspicuous. The differential diagnosis from other forms of tubular basement membrane deposition is discussed.ConclusionDiffuse granular tubular basement membrane immune complex deposition with minimal glomerular involvement is also a manifestation of renal complication in hematopoietic stem cell transplantation recipient. However, the exact mechanism and target antigen remains unknown.

#5710 CHARACTERIZATION OF RESPONSE TO TREATMENT WITH RITUXIMAB IN PATIENTS WITH PRIMARY GLOMERULOPATIES

Abstract Background and Aims Rituximab (RTX) is an anti-CD20 monoclonal antibody used in renal diseases with glomerular involvement, which usually present with proteinuria. The doses used in this pathologies are extrapolated from other diseases such as rheumatoid arthritis, but the optimal regimen in this population has not been well defined. Objective To describe the behaviuor of RITUXIMAB in patients with primary glomerulopathies in whom its use is indicated. Method Descriptive low-intervention single-center clinical trial approved by the Spanish Medicines Agency (NEFRTX, EUDRACT 2020-000484-23. Patients treated with rituximab were included according to medical criteria, prior approval by the Pharmacy Commission. The regimen used was 1g every 15 days, or only 1gr dose with premedication according to clinical practice guidelines. 24-hour blood and urine samples were collected on days 1 (post-rituximab), 7, 15 (pre and post-rituximab), 28, and 45. Serum rituximab was determined using ELISA (Lisa-Traker®-Rituximab, Theraradiag®). Clinical and pharmacokinetic data analyzes were performed considering a single compartment model by non-linear regression with Winnolin® to obtain clearance (Cl), half-life (t1/2), maximum concentration (Cmax) and volume of distribution (Vd). Some quantitative results are expressed as mean ± standard deviation. Linear regression was used to establish correlations. Results The results of 5 patients were analyzed, 2 women and 3 men, with a mean age of 68.8 ± 17.02 years of 72 years and a diagnosis of membranous GN (3), ANCA MPO GN (1), focal and segmental GN (1). Renal function CKD EPI: GFR between 45- 60 ml/min N = 2 GFR >60 ml/min N = 3. According to clinical practice guidelines, patients received 1g doses, 2/5 patients received a second dose on day 15. The evaluation parameters were: proteinuria, CD 19+ lymphocyte depletion, Antibodies titers and histological characteristics as appropriate. levels of rituximab in urine samples after the rituximab administration (15, 30, 180, 365 days after) were determinate. All the patients presented proteinuria, with a mean of 11±14.6 g in 24 h urine. Mean Rituximab clearance was 0.676±0.431 ml/h/kg, distribution volume was 222.35±140.52 mL/Kg and Cmax 69.66±26.14 mcg/mL and t1/2 269.66± 229.71 h (11 days approximately). There is a correlation between proteinuria and rituximab half-life (p = 0.077), as well as between proteinuria and clearance creatinine (p = 0.975) suggesting that half life of rituximab is lower if proteinuria increases (Fig. 1). All presented lymphocyte depletion of CD 19 at 45 days. However, those with more proteinuria >2.5 g (N = 3) in those 45 days, after 6 months of exposure to RTX, progressive repopulation of CD19 was observed, which persisted in the year of follow-up. Conclusion In patients with high proteinuria, rituximab has a t1/2 lower than the 21–28 days described in the data sheet, which may suggest that patients with nephrotic syndrome may require higher doses to ensure the effectiveness of treatment with rituximab. Repopulation of CD19 in 45 days could be a reliable indicator of non response in patients with nephrotic proteinuria.

#4027 KIDNEY INJURY MOLECULE 1 (KIM-1): A POTENTIAL BIOMARKER OF ACUTE KIDNEY INJURY AND TUBULOINTERSTITIAL INJURY IN PATIENTS WITH ANCA-GLOMERULONEPHRITIS

Abstract Background and Aims Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein expressed by proximal tubular cells, recognized as an early, sensitive, and specific urinary biomarker for kidney injury. Blood KIM-1 was recently associated with the severity of acute and chronic kidney damage but its value in ANCA-associated vasculitis with glomerulonephritis (ANCA-GN) has not been studied. Thus, we analyzed its expression at ANCA-GN diagnosis and its relationship with clinical presentation, kidney histopathology, and early outcomes. Method We assessed KIM-1 levels and other pro-inflammatory molecules (CRP, IL-6, TNF-α, MCP-1 and PTX3) at ANCA-GN diagnosis and after 6 months in patients included in the Maine-Anjou registry, which gathers data patients from four French Nephrology Centers diagnosed since January 2000. Results Blood KIM-1 levels were assessed in 58 patients. Levels were elevated at diagnosis and decreased after induction remission therapy. KIM-1 was associated with the severity of renal injury at diagnosis and the need for KRT. In opposition to other pro-inflammatory molecules, KIM-1 correlated with the amount of interstitial fibrosis and tubular atrophy (IF/TA) on kidney biopsy, but not with glomerular involvement. In multivariable analysis, elevated KIM-1 predicted initial eGFR (β = -19 [-31, -7.6], p = 0.002). Conclusion KIM-1 appears as a potential biomarker for acute kidney injury and for tubulointerstitial injury in ANCA-GN. Whether KIM-1 is only a surrogate marker for IF/TA or a key immune player in ANCA-GN pathogenesis remain to be determined.

#4323 A RARE CASE OF MEMBRANOUS NEPHROPATHY AS THE INITIAL PRESENTATION OF SJöGREN SYNDROME

Abstract Introduction Primary Sjögren's syndrome (pSS) is an autoimmune disorder characterized by lymphocytic infiltrates in exocrine glands, most commonly manifesting as dry eyes and mouth. Even though extra glandular involvement can occur in Sjögren, renal involvement is rare. It affects less than 10% of the patient population, with tubulointerstitial nephritis being the usual presentation. Glomerular involvement and, in particular, membranous nephropathy are not commonly encountered. We describe a rare case of membranous nephropathy as the initial presentation of Primary Sjögren's syndrome. Case history A 21-year-old female with a history of sickle cell trait presented to our emergency department with one week history of anasarca. Vital signs were unremarkable, and the physical exam was significant for a 2+ pitting edema of bilateral upper and lower extremities. Initial investigation revealed acute kidney injury (Creatinine 2.9 mg/dl from normal baseline), nephrotic range proteinuria of 6 grams on 24-hour urine collection, and hypoalbuminemia (serum albumin 1.5 mg/dl). Immunological workup showed positive ANA (speckled), strongly positive anti-SSA, borderline elevated anti-SSB, negative anti-PLA2R, negative cryoglobulins, negative anti-dsDNA, and negative anti-Smith antibody (Figure 1). Renal biopsy (Figure 2) revealed membranous nephropathy with acute tubular necrosis (ATN). PLA2R staining was negative. We attributed acute kidney injury to ATN and proteinuria to membranous nephropathy. Negative serologies and renal biopsy findings ruled out systemic Lupus. The patient was therefore diagnosed with membranous nephropathy secondary to pSS. The patient was started on Mycophenolate mofetil and steroid taper with an improvement of proteinuria and anasarca and currently follows at our clinic. Discussion Glomerular involvement is rare, and when involved, it is membranoproliferative glomerulonephritis (MPGN) associated with B-cell activation and positive cryoglobulins. Membranous nephropathy is rare with primary Sjögren syndrome. In our patient, a negative anti-PLA2R goes against primary membranous nephropathy. A negative anti-dsDNA and anti-Smith and biopsy findings essentially rule out Lupus nephritis, leaving Sjögren induced secondary membranous nephropathy as the most likely diagnosis. A literature search revealed few described cases of membranous nephropathy as the presenting feature of pSS with later development of sicca symptoms and progression of renal disease to MPGN. Interestingly, our patient had no sicca symptoms at the presentation time. Occult salivary gland involvement has been described in some of these patients; however, our patient deferred salivary gland biopsy. The management of renal disease in pSS has yet to be well described because of its rarity. Rituximab has shown the most benefit in patients with pSS who have positive cryoglobulins and associated MPGN. Steroids and mycophenolate mofetil (MMF) are other possible agents that can be tried. Given that experience, we started on steroids and MMF with an excellent response to treatment indicated by improvement in proteinuria. Conclusion This case adds to the limited available literature on membranous nephropathy as the initial manifestation of pSS. Although the European Alliance of Associations for Rheumatology (EULAR) criteria strongly emphasizes sicca symptoms and glandular involvement in pSS, the possibility of a small subset of pSS patients who present with early renal involvement with latent glandular findings needs to be recognized.

#5943 THE VALUE OF THE HISTOLOGICAL CLASSIFICATIONS OF ANCA ASSOCIATED VASCULITIS IN PREDICTING LONG TERM KIDNEY SURVIVAL

Abstract Background and Aims Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are a group of multisystemic autoimmune diseases characterized by necrotizing inflammation of small vessels, with a predilection for the kidney. The prognostic value of histological classification of ANCA-glomerulonephritis (ANCA-GN) is discussed. In 2010, Berden and colleagues proposed a prognostic classification based on glomerular involvement; in 2018, Brix et al. introduced the ANCA Renal Risk Score, which includes histological features and glomerular filtration rate; in 2017 the Mayo Clinic Chronicity Score, that considers chronic histological lesions, was designed and assessed in ANCA-GN. We aimed to identify which score is the best tool to predict end-stage kidney disease or death in a cohort of ANCA-GN patients. Method Patients who underwent kidney biopsy in two Italian centers within 32 years were retrospectively collected. Inclusion criteria: age >18 years, and at least one year of follow-up. A minimum of 10 glomeruli was considered adequate for a biopsy. Renal biopsies were classified according to Berden's classification, Renal Risk Score and Mayo Clinic Chronicity Score. The primary end point of the study was the development of end-stage kidney disease (ESKD) at 5 years, defined as the chronic need of renal replacement therapy (RRT) or glomerular filtration rate (GFR) <15 ml/min. The secondary endpoint was a composite endpoint of ESKD or death for all causes. Results Of the 152 patients 84 were male, the median age was 63.8 years (Figure 1). Mean eGFR at diagnosis was 21.32 ml/min/1.73 m2. 32.2% of patients were PR-3 positive, 50.6% were MPO positive, 17.2% were ANCA-negative. After a mean follow-up of 71.7 ± 66.7 months, 59 patients (38.8%) were on chronic dialysis or with a GFR <15 ml/min; among them, 20 patients died. The pure kidney survival rate (without ESKD or GFR<15 ml/min) was 79% at 1 year, 65% at 5 years, 59.8% at 10 years. Figure 2 reported the pure kidney survival rates of the patients assigned to every class of the three scores that we considered in this study. Fig. 3, Fig. 4, Fig. 5 show Kaplan-Meyer curves for the secondary outcome (ESKD+death); patients are classified according to the Berden's score (Fig. 2), the Renal Risk Score (Fig. 3) and Mayo Clinic Chronicity Score (Fig. 4). Conclusion Berden histopathological classification and Renal Risk Score are predictive of renal prognosis when we consider the primary outcome (ESKD or eGFR<15 ml/min) and when we consider the composite outcome (ESKD + death). The Mayo Clinic Chronicity Score allows a reliable stratification of the patients only when we consider the composite outcome (ESKD and death).

#5128 PREDICTIVE FACTORS OF RENAL RECOVERY AND END-STAGE KIDNEY DISEASE IN PATIENTS WITH SEVERE ANCA-ASSOCIATED VASCULITIS WITH GLOMERULONEPHRITIS

Abstract Background and Aims A significant number of patients with anti-neutrophil cytoplasmic antibodies (ANCA) associated vasculitis (AAV) with glomerulonephritis (AAV-GN) still progress to end-stage kidney disease (ESKD, eGFR<15mL/min/1.73m2) despite advances in remission-induction treatment. Method A retrospective cohort study on MPO- or PR3-ANCA positive patients with AAV (MPA or GPA) and ESKD at presentation. Renal recovery, dialysis discontinuation and maintenance in ESKD after standard remission-induction, with or without the use of PLEX were compared. Results We analyzed 166 patients with biopsy proven active kidney involvement and eGFR <15mL/min/1.73m2 at the time of AAV-GN diagnosis. Patients received glucocorticoids with CYC (n = 84) or with RTX (n = 72) for remission-induction, and 49 also received PLEX. The predictors for renal recovery were erythrocyte sedimentation rate, SCr at diagnosis and minimal or mild chronicity changes. We analyzed 71 patients who started dialysis with or without PLEX within 4 weeks from AAV-GN diagnosis. The predictors for dialysis discontinuation were minimal chronicity changes in kidney biopsy at the time of diagnosis (OR 6.138, [95%CI 1.389-27.118],p = 0.017) and focal glomerular involvement (OR 5.017,[95%CI 1.287-19.567],p = 0.020). Predictors for maintenance in ESKD at 12 months included higher serum creatinine (SCr) at the time of diagnosis (IRR 1.086, [95%CI 1.005-1.173],p = 0.037), moderate (IRR 3.797,[95%CI 1.090-13.225],p = 0.036), or severe chronicity changes in kidney biopsy (IRR 5.883,[95%CI 1.542–22.439],p = 0.009). Conclusion In our cohort, kidney recovery, dialysis discontinuation, and maintenance of ESKD in patients with AAV-GN and eGFR<15mL/min/1.73m2 depended on SCr and histologic findings on kidney biopsies at the time of diagnosis and was not affected by the addition of PLEX.