Background: Rheumatoid arthritis (RA) is a systemic inflammatory disorder characterized by joint inflammation, associated with autoantibody production. Renal involvement arises as a complication of treatment or can be related to the disease itself. Methods: 53 biopsies from patients with RA from 1989 to 2015 were reviewed. Histologic diagnosis, age, gender, duration of RA, drug therapy, renal function, proteinuria and haematuria were analyzed. Results: Amyloidosis was the most common renal histologic pattern (21 patients). Membranous Nephropathy (MN) was found in 12 patients, followed by Mesangial Proliferative Glomerulonephritis (n=4) and Focal and Segmental Glomerulosclerosis (n=4), IgA Nephropathy (n=3), Necrotizing Glomerulonephritis (n=3), Chronic Interstitial Nephritis (n=3), Endocapillary Proliferative Glomerulonephritis (n=2) and Minimal Change Disease (n=1). Amyloidosis correlated with long duration RA (14.9±6.66 years vs 8.84±6.37 years; p<0.001), presenting with nephrotic proteinuria in the majority of the cases (5.11±2.94 g/24h vs 3.52±2.71 g/24h p=0.03), which correlates with dominant glomerular amyloid deposition (7.0±2.28 g/24h vs 3.04±2.08 g/24h; p<0.001). In patients with MN, renal function was preserved (serum creatinine 0.83±0.21mg/dl vs 2.03±0.21mg/dl; p<0.001) and one third of the cases presented with haematoproteinuria. Disease modifying antirheumatic drugs (DMARDs) could be related with MN in six cases. Patients with Necrotizing Glomerulonephritis had a severe renal involvement, as did patients with Chronic Interstitial Nephritis. Conclusion: We found a wide spectrum of histological lesions that cannot be predicted with only clinical and laboratory findings. Thus, renal biopsy is essential to ensure correct diagnosis in RA patients who present with urinary abnormalities or deteriorated renal function

ABSTRACT Renal involvement is a common and severe feature of ANCA-associated vasculitis, leading to end-stage kidney disease and death in a considerable number of patients. One of the challenges of ANCA-associated glomerulonephritis is to establish histological features of prognostic value, in order to identify patients who will benefit of immunosuppression. Although the prognostic value of the renal biopsy in ANCA-associated glomerulonephritis is widely recognized, there is no consensus regarding its pathologic classification. In 2010, Berden et al (J Am Soc Nephrol. 2010; 21: 1628-36) proposed a histopathologic classification based only on glomerular morphology, which is of prognostic value for short-term and long-term renal outcomes. However, over the last years, the results of several studies using multivariable approaches have suggested that the proposed histopathologic classes alone might not be sufficient to predict renal outcome. In order to refine the prognosis of patients with ANCA-associated vasculitis, in 2018, Brix et al (Kidney Int. 2018;94:1177-88) proposed the Renal Risk Score, based on clinical and pathological parameters. In this review, we discuss the prognostic value of the Histopathologic Classification and the Renal Risk Score and their role in routine clinical practice.

Anti-glomerular basement membrane (anti-GBM) disease is an aggressive small vessel vasculitis usually mediated by IgG autoantibodies. We describe the case of a 73-year-old male with rapidly progressive renal failure that was diagnosed with IgA mediated anti-GBM disease associated with circulating anti-neutrophil cytoplasm antibodies (ANCA), where the diagnosis was established on kidney biopsy by detecting linear deposition of IgA along the GBM on immunofluorescence microscopy. Despite an intensive immunosuppressive regimen with plasmapheresis, steroids and oral cyclophosphamide, the disease progressed to end-stage renal failure and the patient was started on hemodialysis.

IgG4‑related disease (IgG4‑RD) is an immune‑mediated, inflammatory condition that can affect multiple organs, marked by lymphoplasmocytic infiltration and IgG4‑positive plasma cells. Elevated serum IgG4 is common but not essential. Sole renal manifestation is rare, usually appearing as tubulointerstitial nephritis (TIN) or, less commonly, membranous nephropathy (MN). We present a case of an 87‑year‑old man with a medical history of hypertension, dyslipidemia, ischemic cardiomy‑ opathy, and COPD. The patient presented with nephrotic syndrome (proteinuria/creatininuria ratio (P/C ratio) of 11 g/g) and acute kidney injury (creatinine 4 mg/dL). Urinalysis indicated proteinuria and haematuria without dysmor‑ phic erythrocytes. Investigation revealed normochromic normocytic anaemia, hypoalbuminemia, and no evidence of monoclonal gammopathy or hypocomplementemia. Serologies for HIV, hepatitis B, and hepatitis C were negative. An‑ tinuclear, anti‑neutrophil, and anti‑phospholipase A2 antibodies (anti‑PLA2r) were also negative. Treatment including anti‑proteinuric and anticoagulation therapies was initiated. Kidney biopsy displayed membranous nephropathy and interstitial nephritis; immunofluorescence showed parietal granular deposits of IgG‑κ and IgG‑λ; immunohistochemistry revealed lymphocytes, plasma cells (with more than 10 IgG4‑positive cells per high‑power field), and IgG4 deposits on the glomerular basement membrane. Serum IgG subclass levels detected a slight elevation of IgG4. Other organ involvements hinting at IgG4‑RD were ruled out. Assuming IgG4‑RD with renal involvement therapy with prednisolone (40 mg/day) was started and after one month the patient demonstrated a significant improvement in kidney function, anaemia, hypoalbuminemia, and proteinuria. Although renal manifestation as the first and/or only manifestation of IgG4‑RD is rare, should be suspected in renal cases showing MN with or without TIN, especially when anti‑PLA2R is negative.

Waldenstrom’s macroglobulinemia (WM) is an IgM associated lymphoplasmacytic lymphoma and kidney disease is a rare complication. We report a case of a 41-year-old male with a history of WM diagnosed 16 years ago, currently with no indication for treatment. The patient presented with nephrotic syndrome and acute kidney injury, hypertension, and multiple lymphadenopathies. A kidney biopsy was performed, showing minimal change disease with lymphomatous infiltration of B-lymphocytes CD20+. Therapy with bortezomib, dexametahasone and rituximab was started and after 6 months of follow-up he presented progressive recovery of renal function and remission of proteinuria. This case illustrates the importance of screening renal disease in WM patients. A kidney biopsy should be performed in those presenting with otherwise unexplained renal failure and/or nephrotic syndrome.

Novel oral anticoagulants (NOAC) are a group of drugs recently approved for the treatment of patients at high risk of arterial or venous thrombosis. Unlike vitamin K antagonists, NOAC have a faster onset of action, less drug interactions and do not need frequent monitoring, making their prescription more convenient for physicians and patients. However, both classes of drugs have the potential for nephrotoxicity. Anticoagulation-related nephropathy is a form of acute kidney injury caused by excessive anticoagulation, resulting in glomerular haemorrhage and tubular obstruction by red blood casts. It was first described with warfarin, but new cases have been reported with acenocumarol and dabigatran. We report a case of a 82-year-old woman suffering from atrial fibrillation under rivaroxaban treatment with previous normal renal function, admitted to our unit with gross haematuria and acute kidney injury. A renal biopsy revealed typical features of anticoagulant-related nephropathy superimposed on chronic interstitial nephritis and hypertensive nephroangiosclerosis. There was no recovery of renal function despite withdrawal of rivaroxaban and the patient started on chronic haemodialysis three months after initial episode. To the best of our knowledge, this is the first case of a patient with a biopsy-proven anticoagulant nephropathy related to rivaroxaban. As novel oral anticoagulants are increasingly being prescribed and available data on their safety concerning renal toxicity are scarce, this report highlights the importance of a cautious prescription of these drugs and regular clinical and laboratory evaluation to avoid poor clinical outcomes.

Abstract IgG4‑related disease (IgG4‑RD) is an immune‑mediated, inflammatory condition that can affect multiple organs, marked by lymphoplasmocytic infiltration and IgG4‑positive plasma cells. Elevated serum IgG4 is common but not essential. Sole renal manifestation is rare, usually appearing as tubulointerstitial nephritis (TIN) or, less commonly, membranous nephropathy (MN). We present a case of an 87‑year‑old man with a medical history of hypertension, dyslipidemia, ischemic cardiomyopathy, and COPD. The patient presented with nephrotic syndrome (proteinuria/creatininuria ratio (P/C ratio) of 11 g/g) and acute kidney injury (creatinine 4 mg/dL). Urinalysis indicated proteinuria and haematuria without dysmorphic erythrocytes. Investigation revealed normochromic normocytic anaemia, hypoalbuminemia, and no evidence of monoclonal gammopathy or hypocomplementemia. Serologies for HIV, hepatitis B, and hepatitis C were negative. Antinuclear, anti‑neutrophil, and anti‑phospholipase A2 antibodies (anti‑PLA2r) were also negative. Treatment including anti‑proteinuric and anticoagulation therapies was initiated. Kidney biopsy displayed membranous nephropathy and interstitial nephritis; immunofluorescence showed parietal granular deposits of IgG‑κ and IgG‑λ; immunohistochemistry revealed lymphocytes, plasma cells (with more than 10 IgG4‑positive cells per high‑power field), and IgG4 deposits on the glomerular basement membrane. Serum IgG subclass levels detected a slight elevation of IgG4. Other organ involvements hinting at IgG4‑RD were ruled out. Assuming IgG4‑RD with renal involvement therapy with prednisolone (40 mg/day) was started and after one month the patient demonstrated a significant improvement in kidney function, anaemia, hypoalbuminemia, and proteinuria. Although renal manifestation as the first and/or only manifestation of IgG4‑RD is rare, should be suspected in renal cases showing MN with or without TIN, especially when anti‑PLA2R is negative.

ABSTRACT Renal cortical necrosis (RCN) is a rare cause of acute kidney injury (AKI) in developed countries. Drugs, especially non-steroidal antiinflammatory drugs, (NSAIDs) are very rarely described in the literature to cause cortical necrosis. It is characterized by confluent necrosis of the entire cortex apart from a thin rim of viable tissue in the subcapsular, juxtaglomerular areas, and medulla. Although the pathogenesis of the disease remains unclear, the final common pathway is permanent occlusion of afferent arterioles and interlobular arteries in the cortical vasculature. NSAIDs are widely prescribed in general clinical practice. Despite being readily available, a subset of individuals is susceptible to serious renal toxicity and caution should be exercised when these drugs are used. We present the case of a young adult who presented with renal cortical necrosis with irreversible renal failure. Unfortunately, it occurred as a result of inappropriate use of over-the-counter NSAIDs in the setting of the pandemic outbreak of COVID-19.