Acute postinfectious glomerulonephritis in the modern era: experience with 86 adults and review of the literature

Drowning in Fluid: Post-infectious Glomerulonephritis Presenting as Acute Heart Failure

Staphylococcal infection is as common as streptococcal infection as a cause of infection-related glomerulonephritis (IRGN). It is seen more frequently in the pediatric population and is relatively rare in adults. Glomerular disease manifests as either nephritic or nephrotic syndrome. A high index of suspicion is necessary for diagnosing this condition as it can be mistaken for other common conditions in the elderly. IRGN may present as volume overload and may masquerade as cardiorenal syndrome type 1 in patients with preexisting heart failure, emphasizing the importance of distinguishing between the two because the treatment and prognosis may be different. We present an older adult male who was evaluated for suspected acute decompensation of heart failure in the setting of recent left knee septic arthritis and was found to have IRGN. This diagnosis may be delayed or missed due to it mimicking similar conditions and it requires a high index of suspicion.

Acute kidney injury and ANCA positivity in a patient treated with glecaprevir/pibrentasvir: a case report

Background

Glecaprevir/pibrentasvir is an effective antiviral therapy for hepatitis C virus infection and is generally regarded safe in patients with renal impairment. However, renal complications are a notable, albeit rare, concern.

Case presentation

We report a case of acute kidney injury in a man in his 50s with chronic hepatitis C virus, chronic obstructive pulmonary disease, morbid obesity, a history of heroin dependence, and untreated type 2 diabetes mellitus. About four weeks into an eight-week glecaprevir/pibrentasvir regimen he developed progressive lower extremity edema, bullae, and skin ulcers with worsening renal function. His serum creatinine rose to 4.46 mg/dL and blood urea nitrogen to 44 mg/dL. ANCA serology revealed dual perinuclear and cytoplasmic positivity, though anti-proteinase 3 and anti-myeloperoxidase antibody tests were negative. Kidney biopsy revealed diffuse tubulointerstitial injury with erythrocyte casts indicative of glomerular bleeding into the distal nephrons, though without glomerular crescent formation.

Conclusion

This case illustrates the potential for glecaprevir/pibrentasvir to induce acute kidney injury, acute interstitial nephritis and possibly ANCA-associated vasculitis. Recognizing these adverse renal effects is critical for making timely diagnosis and management in hepatitis C virus patients undergoing antiviral therapy.

A Rare Clinical Entity: Staphylococcus-Related Glomerulonephritis

Staphylococcus aureus is a rare cause of postinfectious glomerulonephritis, and Staphylococcus-related glo-merulonephritis primarily occurs in middle-aged or elderly patients. Patients with Staphylococcus-related glomerulonephritis also present with hematuria, proteinuria of varying degrees, rising serum creatinine levels, and/or edema. The severity of renal insufficiency is proportional to the degree of proliferation and crescent formation. Here, we present a diabetic patient admitted with a history of 1 week of left elbow pain. Laboratory results revealed that erythrocyte sedimentation rate was 110 mm/hour, serum creatinine level was 1 mg/dL, C-reactive protein level was 150 mg/L, and magnetic resonance imaging showed signal changes in favor of osteomyelitis at the olecranon level, with diffuse edematous appearance in the elbow skin tissue and increased intra-articular effusion. After diagnosis of osteomyelitis, ampicillin/sulbactam and teicoplanin were administered. After day 7 of admission, the patient developed acute kidney injury requiring hemodialysis under antibiotic treatment. Kidney biopsy was performed to determine the underlying cause, which showed Staphylococcus-related glomerulonephritis. Recovery of renal func-tions was observed after antibiotic and supportive treatment.

Case Series of Infection-Related Glomerulonephritis in Quebec Indigenous Peoples

Rationale

Infection-related glomerulonephritis (IRGN) is an immune-mediated glomerulonephritis caused by extra-renal infectious diseases. There has been an important shift in epidemiology in recent years, with a significant proportion of adults affected. The incidence of IRGN is higher amongst Indigenous populations and especially in those with multiple comorbidities. Beginning in 2019, we observed several IRGN cases amongst adult Indigenous peoples referred to the McGill University Health Center (MUHC). The aim of this article is to describe the demographic, clinical, and outcome data of these individuals and highlight the heterogeneity of IRGN in this population through 2 illustrative cases.

Presenting concerns of the patient

In total, 8 cases of IRGN were identified between 2019 and 2022. All patients presented with features of acute glomerulonephritis.

Diagnoses

All patients had documented evidence of an infection that preceded their diagnosis of IRGN. IRGN was not the initial clinical diagnosis in all cases.

Interventions

Half the patients received immunosuppression while the others received supportive care only.

Outcomes

Four patients required initiation of hemodialysis at time of presentation and at 2 years of follow-up, 3 of the 4 remained hemodialysis-dependent.

Teaching points

Our case series emphasizes the heterogenous clinical, laboratory, and pathological presentations that make the diagnosis of IRGN quite challenging. A high index of suspicion should be present when a patient presents with acute kidney injury, features of a glomerulonephritis, and an infection, especially those with multiple comorbidities and a preceding history of chronic kidney disease.

Parvovirus B19-related membranoproliferative glomerulonephritis presenting with positive glomerular staining for nephritis-associated plasmin receptor: a case report and review of the literature

Several cases of glomerulonephritis occurring after infection with human parvovirus B19 (PVB19) have been reported. However, the pathogenesis and clinicopathological features of PVB19-related glomerulonephritis remain elusive. We describe the case of a 34 year-old woman who showed nephrotic syndrome and microscopic hematuria 10 days after PVB19 infection. Blood pressure and renal function were within normal ranges. Laboratory tests showed positive results for anti-PVB19 immunoglobulin (Ig)M antibody and complement 3 (C3) hypocomplementemia. Antibody to streptolysin O (ASO) was slightly elevated, but bacterial cultures yielded no colonies. Light microscopy of renal biopsy was compatible with membranoproliferative glomerulonephritis (MPGN). Immunofluorescence microscopy showed intense staining for C3 and faint staining for IgG on the glomerular capillary wall and paramesangial area. Electron micrography showed subendothelial electron-dense deposits (EDDs), but hump-shaped subepithelial EDDs were not evident. PBV19-DNA was absent from renal tissue. Moreover, glomeruli showed positive staining for nephritis-associated plasmin receptor (NAPlr) and plasmin activity with similar distribution. Around 6 months after PVB19 infection, levels of anti-PVB19 IgM antibody spontaneously tuned negative with an apparent reduction of proteinuria and improvement of hypocomplementemia, although ASO level remained unchanged. This appears to represent the first description of positive glomerular staining for NAPlr in MPGN after PVB19 infection. Based on a review of 27 cases, including our own case, the MPGN lesions could be attributable to PVB19 infection. Clinicopathological features of this case were incompatible with post-streptococcal acute glomerulonephritis. We presume that a PBV19-derived glomerular pathogen that cross-reacts with anti-NAPlr antibody might be involved in the development of PVB19-related MPGN.

Rapidly Progressive Glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN) is a syndrome characterized by a swift decline in kidney function, often over a few months, accompanied by features of nephritic syndrome. It can result in decreased urine output and commonly involves the presence of extensive crescents in kidney biopsies. RPGN is classified into 3 main types based on immune deposit distribution and visualization through immunofluorescence and electron microscopy: antiglomerular basement membrane disease, immune complex glomerulonephritis, and pauci-immune glomerulonephritis. Early diagnosis and prompt treatment are critical to prevent progression to ESRD. Standard treatment options for RPGN include glucocorticoids, cyclophosphamide, or rituximab, with plasma exchange especially important for antiglomerular basement membrane disease and select cases of ANCA-associated vasculitis. Clinical trials for glomerular diseases have primarily excluded patients with RPGN or dialysis dependence. Establishment of clinical registries is required for the optimization of therapeutic protocols for the treatment of RPGN.

Short-Term Outcomes of Infection-Related Glomerulonephritis in Diabetes Mellitus

Background and objective Infection-related glomerulonephritis (IRGN) in adults, particularly the diabetic population, has a grave prognosis with many patients progressing to dialysis-dependent renal failure. Indian data on this entity are very scarce. This study attempts to correlate the clinicopathological factors related to diabetic IRGN and its short-term outcomes. Subjects and methods A retrospective analysis of all diabetic patients with biopsy-proven IRGN between January 2017 and August 2021 was conducted. Factors affecting outcomes such as clinical characteristics, urine examination, complete blood count, serum biochemistry, renal biopsy, and follow-up data were obtained and analyzed to determine the risk of progression to chronic kidney disease (CKD)/end-stage renal disease (ESRD). Univariate/multivariate analysis and receiver operating characteristic (ROC) curve were performed to identify independent risk factors affecting outcomes. Results A total of 40 diabetic patients with IRGN was included in the study, with a mean age of 53.08 ± 10 years, comprising predominantly males (60%). Infective foci were occult in majority (37.5%). Isolated low C3 levels were documented in the majority, while three patients (7.5%) had normal complement levels. Complete renal recovery was noted in 15 patients (37.5%), while 12 patients (30%) progressed to ESRD. Anuria or uremia at presentation, glomerulosclerosis >28.6%, interstitial fibrosis with tubular atrophy (IFTA) >17.5%, and diabetic nephropathy correlated to poor renal recovery. No correlation was observed between endocapillary proliferation, the pattern of deposits, the prevalence of crescents, and complement levels with the outcome. Conclusion IRGN is a common immune-mediated clinical entity among diabetics and often requires renal replacement therapy. Anuria or uremia at presentation, diabetic nephropathy, elevated glomerulosclerosis, and IFTA were associated with poor renal recovery. Complement levels and crescents had no impact on the outcome.

The Pulsing Paradox: Successful Steroid Therapy in Infection-Related Glomerulonephritis

The patterns of infection-related glomerulonephritis (IRGN) are rapidly changing in terms of age at presentation and sources of infection. The existing literature on the use of steroids in IRGN is inconsistent. A diabetic male in his sixties presented with features of anasarca, bilateral flank pain, and acute pulmonary edema. He had a non-healing ulcer over his right leg, with pus culture showing growth of methicillin-resistant Staphylococcus aureus (MRSA). Computed tomography (CT) of the kidneys, ureter, and bladder (KUB) showed features of bilateral pyelonephritis. The patient went on to develop acute renal failure and eventually required hemodialysis. A renal biopsy was performed, and features of IRGN with crescents were noted. Considering the presence of crescents in renal biopsy, a trial of steroids was given under antibiotic cover, which resulted in a near-complete resolution of renal failure.

Infection-Associated Glomerulonephritis

The nephritic syndrome has been associated with a wide variety of infections, spanning many organisms and myriad clinical presentations. Infection-associated glomerulonephritis is challenging to diagnose given the many confounding factors linking kidney injury to infection; however, urine microscopy can assist in identifying abnormal cellular elements suggestive of glomerulonephritis. Kidney biopsy remains the gold standard for diagnosing the underlying pathologic lesion. Treatment of infection-associated glomerulonephritis centers around aggressive and complete treatment of the underlying infectious driver. It is often hard to know exactly when immunosuppression may be required in addition to treating the infection.

IgA-Dominant Staphylococcus-Associated Glomerulonephritis: An Uncommon Complication of Intravenous Drug Use

A 24-year-old female with a history of intravenous heroin use presented with two weeks of chills, myalgias, and cough and was found to be in acute hypoxemic respiratory failure. Subsequent workup revealed the presence of bilateral septic pulmonary emboli and tricuspid valve endocarditis. Several weeks into her hospitalization, she developed periorbital edema and laboratory testing revealed she had developed acute renal failure and nephrotic range proteinuria. A renal biopsy confirmed the diagnosis of IgA-dominant Staphylococcus-associated glomerulonephritis (IgA-SAGN). Early recognition of this newly recognized variant of glomerulonephritis is paramount, as improper treatment may lead to catastrophic consequences.

The role of N-methyladenosine modification in acute and chronic kidney diseases

N6-methyladenosine (m6A) modification is a kind of RNA modification in which methylation occurs at the sixth N position in adenosine in RNA, which can occur in various RNAs such as mRNAs, lncRNAs and miRNAs. This is one of the most prominent and frequent posttranscriptional modifications within organisms and has been shown to function dynamically and reversibly in a variety of ways, including splicing, export, attenuation and translation initiation efficiency to regulate RNA expression. There are three main enzymes associated with m6A modification: writers, readers and erasers. Increasing evidence has shown that m6A modification is associated with the onset and development of kidney disease. In this article, we address the important physiological and pathological roles of m6A modification in kidney diseases (uremia, ischemia-reperfusion kidney injury, drug-induced kidney injury, and diabetic nephropathy) and its molecular mechanisms to provide reference for the diagnosis and clinical management of kidney diseases.

IgA-dominant postinfectious glomerulonephritis: a case report

Introduction

Acute postinfectious glomerulonephritis (APIGN) is an immunological glomerular disease that is an important health issue in developing countries. The incidence remains high in developing countries with a male-to-female ratio of 2:1 and age predominantly above 50 years. In this case study, we present a patient with a history of Staphylococcus epidermidis infection, a past medical history of diabetes mellitus, and histopathological findings of APIGN with Immunoglobulin A (IgA) deposition.

Methods

A 58-year-old male presented to the emergency room with a 6-day history of severe low back pain. Three days later, the patient developed fever, chills, abdominal pain in the upper quadrant and a subsequent lower limb cellulitis. Various immunological tests, imaging studies, and kidney biopsy were performed to arrive at a diagnosis.

Results

Following the diagnosis and treatment of Cholangitis and Staphylococcus epidermidis, further investigation led to a diagnosis of IgA-dominant APIGN. IgA-dominant APIGN was treated with antibiotics, renin-angiotensin-aldosterone system inhibitors and steroids, and the patient was discharged from the hospital.

Conclusion

In developing countries, APIGN is a relatively common presentation of kidney damage due to acute kidney injury and nephritic syndrome. IgA-dominant APIGN is a rare but increasingly recognized morphological variant in which IgA is the sole or dominant immunoglobulin. This unique presentation and multidisciplinary approach for diagnosing and treating IgA-dominant APIGN need to be considered and understood by healthcare professionals to better help these patients. Further investigation is needed to understand the best treatment of this IgA-dominant APIGN presentation and its prognosis.

IgA-dominant infection-related glomerulonephritis with NAPlr-positive tubulointerstitial nephritis

Infection-related glomerulonephritis (IRGN) is one of the most common causes of acute kidney injury (AKI). Positive glomerular staining of the nephritis-associated plasmin receptor (NAPlr) has been reported as a useful biomarker of IRGN. Although the infection can provoke acute tubulointerstitial nephritis (AIN), there are few reports of positive staining for NAPlr with AIN. We report a case of methicillin-sensitive Staphylococcus aureus (MSSA) infection-related nephritis complicated with AIN, which showed positive staining for tubulointerstitial NAPlr. The patient developed AKI and nephrotic syndrome during an intraperitoneal MSSA infection. A diagnosis of IRGN complicated by infection-related acute tubulointerstitial nephritis (IRAIN) was made based on glomerular endocapillary proliferation with tubulointerstitial infiltrating cells and tubular atrophy. Tubulointerstitial infiltrating cells were positive for NAPlr staining and plasmin activity. Treatment of the infection by antibiotics and drainage did not improve the AKI, but steroid administration improved that. NAPlr evaluation is a helpful tool for identifying causes of AIN during infection.

Bacterial infection-related glomerulonephritis in patients with diabetes

AIM

Diabetic patients are prone to infections, thus making them a unique cohort at risk of developing bacterial infection-related glomerulonephritis (IRGN).

METHODS

In total, 1693 adult diabetic patients underwent kidney biopsy between 2005 and 2021 at our tertiary care hospital in South India. Of these, 121 consecutive cases which met criteria of bacterial IRGN were included in this study.

RESULTS

The mean age of the cohort was 53.1 ± 10.1 years and 83/121 (68.5%) were males. Majority (98.3%) had type 2 diabetes for a median duration of 6 (IQR, 2-12) years. The most common sites of infection were skin (47/121, 38.8%) and urinary tract (15/121, 12.4%). Fifty percent (58/121) of patients had underlying advanced diabetic kidney disease (DKD). Isolated C3 deposits (without immunoglobulin) occurred in 66/121 (54.5%) patients predominantly in advanced DKD patients. IgA-dominant glomerulonephritis occurred in only 9/121 (7.4%) patients. Short-course oral steroid was given to 86/121 (71.1%) patients. Steroid related dysglycemia and immunosuppression related infections occurred in 9/61 (14.8%) and 16/61 (26.2%) patients respectively. Of the 90 patients with follow up details >3 months, 46 (51.1%) progressed to kidney failure over a median period of 0.5 (IQR, 0-7.2) months. Patients diagnosed in the latter half of our study period (2013-2021) were older, less commonly presented with fever, had more pronounced hypocomplementemia and severe renal histology predominantly with a 'starry sky' immunofluorescence pattern.

CONCLUSION

Superimposed bacterial IRGN on underlying DKD is associated with poor renal outcomes. Use of short course steroid was associated with significant toxicity.

Autoimmunity and Infection in Glomerular Disease

The ongoing glomerular damage of infections is not limited to the most widely known form of post-streptococcal glomerulonephritis, which is today less common in the Western world; other forms of glomerulonephritis are associated with several bacterial, viral and parasitic pathogens. The mechanisms responsible range from the direct damage of glomerular cells to the formation and deposition of immunocomplexes to molecular mimicry to the secretion of superantigens. Similarly, in the course of glomerular disease, infections are more frequent than in the general population due to the loss of immunoglobulins in urine and the immunosuppressive agents used to treat the autoimmune disease that decrease the activity of the immune system. Recognizing this two-way link, understanding its pathogenetic mechanism, and identifying the most appropriate therapeutic choice are essential for the personalized management of patients. In this continuously developing field, this short review summarizes the current state of the art as support for physicians, who are increasingly involved in managing patients with glomerular disease and infections.

Infection-Related Glomerulonephritis in Children and Adults

Infection-related glomerulonephritis is an immunologically mediated glomerular injury after an infection. Glomerulonephritis may occur with the infection or after a variable latent period. Poststreptococcal glomerulonephritis (PSGN) is the prototype of infection-related glomerulonephritis. The streptococcal antigens, nephritis-associated plasmin-like receptor and streptococcal exotoxin B, have emerged as major players in the pathogenesis of PSGN. Although PSGN is the most common infection-related glomerulonephritis in children, in adults, glomerulonephritis is secondary to bacteria such as staphylococci, viruses such as hepatitis C, and human immunodeficiency virus, and, rarely, parasitic infections. Supportive therapy is the mainstay of treatment in most infection-related glomerulonephritis. Treatment of the underlying infection with specific antibiotics and antiviral medications is indicated in some infections. Parasitic infections, although rare, may be associated with significant morbidity. Poststreptococcal glomerulonephritis is a self-limiting condition with a good prognosis. However, bacterial, viral, and parasitic infections may be associated with significant morbidity and long-term consequences. Epidemiologic studies are required to assess the global burden of infection-related glomerulonephritis. A better understanding of the pathogenesis of infection-related glomerulonephritis may unravel more treatment options and preventive strategies.

Systemic Haemophilus parainfluenzae Infection Manifesting With Endocarditis and Membranoproliferative Glomerulonephritis

Infective endocarditis (IE) is a potentially fatal disease that is primarily caused by Staphylococci and Streptococci. The HACEK group of bacteria (Hemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae) account for only 1-3% of reported IE cases. IE has long been known to cause glomerulonephritis. The most common histologic patterns seen are crescentic and diffuse proliferative glomerulonephritis. Notably, membranoproliferative glomerulonephritis (MPGN) is one of the less common patterns seen with IE. We present a rare case of MPGN associated with Haemophilus parainfluenzae endocarditis. A 56-year-old male with no significant past medical history presented to a local hospital with complaints of fever, night sweats, dyspnea, diarrhea, and dark urine for about a month. He was found to have a hemoglobin of 4g/dL, requiring multiple transfusions. He also had bilateral pleural effusions and pulmonary edema. In the following days, he had worsening renal function and was transferred to our hospital for further workup. Initial labs showed anemia, thrombocytopenia, and leukocytosis. He had creatinine elevated at 5.28 mg/dL and a low estimated glomerular filtration rate (eGFR) of 12 mL/min/1.73m². Urinalysis showed proteinuria, urine hemoglobin, urine white blood cells (WBCs), and red blood cells (RBCs). Blood cultures revealed H. parainfluenzae. Transesophageal echocardiogram (TEE) showed large vegetations with perforation of the mitral valve leaflet. Serology showed low complement levels. Renal biopsy displayed a membranoproliferative pattern of glomerulonephritis on light microscopy. The hepatitis panel was negative, as was the autoimmune workup. The patient was diagnosed with MPGN associated with H. parainfluenzae endocarditis. His complex clinical course required mitral valve replacement and aortic valve repair. He completed the course of antibiotics, with improvement in renal and cardiac function.

Clinico-Pathogenic Similarities and Differences between Infection-Related Glomerulonephritis and C3 Glomerulopathy

Recently, the comprehensive concept of "infection-related glomerulonephritis (IRGN)" has replaced that of postinfectious glomerulonephritis (PIGN) because of the diverse infection patterns, epidemiology, clinical features, and pathogenesis. In addition to evidence of infection, hypocomplementemia particularly depresses serum complement 3 (C3), with endocapillary proliferative and exudative GN developing into membranoproliferative glomerulonephritis (MPGN); also, C3-dominant or co-dominant glomerular immunofluorescence staining is central for diagnosing IRGN. Moreover, nephritis-associated plasmin receptor (NAPlr), originally isolated from the cytoplasmic fraction of group A Streptococci, is vital as an essential inducer of C3-dominant glomerular injury and is a key diagnostic biomarker for IRGN. Meanwhile, "C3 glomerulopathy (C3G)", also showing a histological pattern of MPGN due to acquired or genetic dysregulation of the complement alternative pathway (AP), mimics C3-dominant IRGN. Initially, C3G was characterized by intensive "isolated C3" deposition on glomeruli. However, updated definitions allow for glomerular deposition of other complement factors or immunoglobulins if C3 positivity is dominant and at least two orders of magnitude greater than any other immunoreactant, which makes it challenging to quickly distinguish pathomorphological findings between IRGN and C3G. As for NAPlr, it was demonstrated to induce complement AP activation directly in vitro, and it aggravates glomerular injury in the development of IRGN. A recent report identified anti-factor B autoantibodies as a contributing factor for complement AP activation in pediatric patients with PIGN. Moreover, C3G with glomerular NAPlr deposition without evidence of infection was reported. Taken together, the clinico-pathogenic features of IRGN overlap considerably with those of C3G. In this review, similarities and differences between the two diseases are highlighted.

The Diagnostic Conundrum of Glomerular Crescents With IgA Deposits

INTRODUCTION

Glomerulonephritis (GN) with crescents and IgA deposits in kidney biopsy poses a frequent diagnostic and therapeutic dilemma because of multiple possibilities.

METHODS

Native kidney biopsies showing glomerular IgA deposition and crescents (excluding lupus nephritis) were identified from our biopsy archives between 2010 and 2021. Detailed clinicopathologic features were assessed. One-year clinical follow-up on a subset of cases was obtained.

RESULTS

A total of 285 cases were identified, and these clustered into IgA nephropathy (IgAN, n = 108), Staphylococcus or other infection-associated GN/infection-related GN (SAGN/IRGN, n = 43), and antineutrophil cytoplasmic antibody-associated GN (ANCA-GN, n = 26) based on a constellation of clinicopathologic features, but 101 cases (group X) could not be definitively differentiated. The reasons have been elucidated, most important being atypical combination of clinicopathologic features and lack of definitive evidence of active infection. Follow-up (on 72/101 cases) revealed that clinicians' working diagnosis was IgAN in 43%, SAGN/IRGN in 22%, ANCA-GN in 28%, and others in 7% of the cases, but treatment approach varied from supportive or antibiotics to immunosuppression in each subgroup. Comparing these cases as "received immunosuppression" versus "non-immunosuppression," only 2 features differed, namely C3-dominant staining, and possibility of recent infection (both higher in the no-immunosuppression group) (P < 0.05). Renal loss was higher in the non-immunosuppression subgroup, but not statistically significant (P = 0.11).

CONCLUSION

Diagnostic overlap may remain unresolved in a substantial number of kidney biopsies with glomerular crescents and IgA deposits. A case-by-case approach, appropriate antibiotics if infection is ongoing, and consideration for cautious immunosuppressive treatment for progressive renal dysfunction may be needed for best chance of renal recovery.

Non-Diabetic Kidney Disease in Type 2 Diabetes Mellitus: A Changing Spectrum with Therapeutic Ascendancy

BACKGROUND AND OBJECTIVES

Owing to changing epidemiology and therapeutic practices, a change in the spectrum of renal involvement in Type-2 diabetes mellitus (T2DM) has also been noted. The treatment of non-diabetic kidney disease (NDKD) differs from diabetic kidney disease (DKD) and the reversibility of NDKD in many cases to normal, prompts biopsy for rapid and accurate diagnosis. Data are scarce on kidney biopsy findings in T2DM.

STUDY DESIGN & SETTING

In this observational study, we prospectively collected the data of kidney biopsies of patients aged ≥ 18 years with T2DM admitted between 1 August 2005 and 31 July 2022. The clinical, demographic and histopathological data were evaluated. The spectrum of kidney involvement in the form of DKD and/or NDKD was studied. The impact of these findings with the use of drugs retarding disease progression was also analyzed.

RESULTS

A total of 5485 biopsies were performed during the study period and of these 538 patients had T2DM. The mean age of the study population was 56.9 ± 11.5 years and 81% were males. The mean duration of DM was 6.4 ± 6.1 years. Diabetic retinopathy (DR) was noted in 29.7%. The most common indication for biopsy was an acute rise in creatinine (147, 27.3%). Amongst the 538 diabetic patients who underwent biopsy, histological features only of DKD were noted in 166 patients (33%), NDKD alone in 262 (49%) and NDKD with DKD lesions in 110 (20%). On multivariate analysis, duration of DM less than 5 years, absence of CAD, absence of DR, oliguria at presentation, an acute rise in creatinine and low C3 were associated with NDKD.

CONCLUSIONS

The prevalence of NDKD among diabetics and ATIN in particular might be on an increasing trend in the current era of changing T2DM epidemiological patterns. The use of anti-pro-teinuric agents was associated with lesser degrees of histopathological chronicity in T2DM.

Streptococcal Infection-related Glomerulonephritis in an Elderly Diabetic Patient Complicated by Hemophagocytic Syndrome and Cytomegalovirus Nephritis

There has been a significant shift in epidemiology and renal outcomes of infection-related glomerulonephritis (IRGN) in recent years. The renal prognosis of IRGN is often poor in adults, especially in the elderly and diabetics. We herein report an elderly diabetic patient with IRGN due to streptococcal infection complicated by hemophagocytic syndrome and cytomegalovirus nephritis, which is uncommon among non-transplant patients. Infection control and steroids did not recover the patient's renal function. For elderly IRGN patients with diabetes, a further investigation of the most effective treatment for related renal outcomes is needed.

Kidney diseases

Dysregulation and accelerated activation of the alternative pathway (AP) of complement is known to cause or accentuate several pathologic conditions in which kidney injury leads to the appearance of hematuria and proteinuria and ultimately to the development of chronic renal failure. Multiple genetic and acquired defects involving plasma- and membrane-associated proteins are probably necessary to impair the protection of host tissues and to confer a significant predisposition to AP-mediated kidney diseases. This review aims to explore how our current understanding will make it possible to identify the mechanisms that underlie AP-mediated kidney diseases and to discuss the available clinical evidence that supports complement-directed therapies. Although the value of limiting uncontrolled complement activation has long been recognized, incorporating complement-targeted treatments into clinical use has proved challenging. Availability of anti-complement therapy has dramatically transformed the outcome of atypical hemolytic uremic syndrome, one of the most severe kidney diseases. Innovative drugs that directly counteract AP dysregulation have also opened new perspectives for the management of other kidney diseases in which complement activation is involved. However, gained experience indicates that the choice of drug should be tailored to each patient's characteristics, including clinical, histologic, genetic, and biochemical parameters. Successfully treating patients requires further research in the field and close collaboration between clinicians and researchers who have special expertise in the complement system.

Successful treatment of infectious endocarditis-associated glomerulonephritis during active hepatitis C infection: a case report

BACKGROUND

Hepatitis C virus (HCV) may play a pathogenic role in several forms of immune complex glomerulonephritis (GN). We present a patient whose initial clinical presentation instilled suspicion of HCV-related renal involvement. Yet, histopathologic data oriented towards a different diagnosis.

CASE PRESENTATION

A 68-year old man presented with kidney dysfunction, cryoglobulins, low C4 level, high HCV-RNA and cutaneous vasculitis. The first hypothesis was a hepatitis C-related cryoglobulinemic glomerulonephritis. Renal biopsy revealed endocapillary and mesangial cells hypercellularity with complement C3 and IgM deposits. The echocardiography showed an infectious endocarditis (IE) on aortic valve. Appropriate antibiotic therapy and a prosthetic valve replacement were performed, obtaining recovery of renal function.

CONCLUSION

HCV infection may be linked to multiple renal manifestations, often immune-complex GN such as cryoglobulinemic membrano-proliferative GN. Renal disease due to IE is usually associated to focal, segmental or diffuse proliferative GN, with prominent endocapillary proliferation. The most common infectious agents are Staphylococcus aureus and Streptococcus species. This case report may be relevant because the renal dysfunction was highly suggestive of a cryoglobulinemic GN on a clinical ground, but the histologic pattern after performing the renal biopsy oriented towards a different cause of the underlying disease, that required a specific antibiotic treatment. The renal biopsy is always required to confirm a clinical suspicious in patients affected by multiple comorbidities.

Glomerular Hematuria and the Utility of Urine Microscopy: A Review

Evaluation of hematuria and microscopic examination of urine sediment are commonly used tools by nephrologists in their assessment of glomerular diseases. Certain morphological aspects of urine red blood cells (RBCs) seen by microscopy may help in identifying the source of hematuria as glomerular or not. Recognized signs of glomerular injury are RBC casts or dysmorphic RBCs, in particular acanthocytes (ring-shaped RBCs with protruding blebs). Despite being a highly operator-dependent test, urine sediment examination revealing these signs of glomerular hematuria has demonstrated specificities and positive predictive values ranging between 90%-100% for diagnosing glomerular disease, although sensitivity can be quite variable. Hematuria is a commonly used tool for diagnosing patients with proliferative glomerulonephritis such as IgA nephropathy, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and lupus nephritis, sometimes even as a surrogate for kidney involvement. Studies examining the role for hematuria in monitoring and predicting adverse outcomes in these diseases have shown inconsistent results, possibly due to inconsistent definitions that often fail to consider specific markers of glomerular hematuria such as dysmorphic RBCs, acanthocytes, or RBC casts. A consensus definition of what constitutes glomerular hematuria would help standardize use in future studies and likely improve the diagnostic and prognostic value of hematuria as a marker of glomerulonephritis.

Efficacy of Corticosteroids in Infection-Related Glomerulonephritis–A Randomized Controlled Trial

Introduction

Infection-related glomerulonephritis (IRGN) is associated with glomerular immune complex deposition along with complement activation. Steroids may attenuate glomerular injury and thereby improve renal outcomes.

Methods

We randomly assigned patients who had biopsy-proven IRGN and serum creatinine greater than 1.5 mg/dl to receive corticosteroids plus supportive care (intervention arm), or supportive care alone (control arm). Patients were followed up for 6 months. The primary outcome was complete renal recovery at 6 months. Safety of steroid therapy was also assessed.

Results

A total of 52 patients underwent randomization. At 6 months, 17 of 26 patients (65.4%) in the intervention arm and 14 of 26 patients (53.8%) in the control arm had complete renal recovery (odds ratio 1.6; 95% confidence interval, 0.5–4.9; P = 0.397). There was no statistically significant difference in any of the secondary outcomes. Adverse events occurred in 12 patients (46.2%) in the intervention arm and 2 patients (7.7%) in the control arm (P = 0.002).

Conclusion

In this single-center trial, corticosteroids did not result in a statistically significant increase in rates of complete renal recovery at 6 months. There was a significantly increased risk of adverse events associated with the use of corticosteroids.

Staphylococcus aureus Infection-Related Glomerulonephritis with Dominant IgA Deposition

Since 1995, when we reported the case of a patient with glomerulonephritis with IgA deposition that occurred after a methicillin-resistant Staphylococcus aureus (MRSA) infection, many reports of MRSA infection-associated glomerulonephritis have accumulated. This disease is being systematized as Staphylococcus infection-associated glomerulonephritis (SAGN) in light of the apparent cause of infection, and as immunoglobulin A-dominant deposition infection-related glomerulonephritis (IgA-IRGN) in light of its histopathology. This glomerulonephritis usually presents as rapidly progressive glomerulonephritis or acute kidney injury with various degrees of proteinuria and microscopic hematuria along with an ongoing infection. Its renal pathology has shown several types of mesangial and/or endocapillary proliferative glomerulonephritis with various degrees of crescent formation and tubulointerstitial nephritis. IgA, IgG, and C₃ staining in the mesangium and along the glomerular capillary walls have been observed on immunofluorescence examinations. A marked activation of T cells, an increase in specific variable regions of the T-cell receptor β-chain-positive cells, hypercytokinemia, and increased polyclonal immune complexes have also been observed in this glomerulonephritis. In the development of this disease, staphylococcal enterotoxin may be involved as a superantigen, but further investigations are needed to clarify the mechanisms underlying this disease. Here, we review 336 cases of IgA-IRGN and 218 cases of SAGN.

Acute Post-Streptococcal Glomerulonephritis In Children: A Comprehensive Review

BACKGROUND

Acute post-streptococcal glomerulonephritis (APSGN) is an immune-complex (ICs) mediated glomerular disease triggered by group A β-hemolytic streptococcus (GAS) or Streptococcus pyogenes infections. APSGN represents a major cause of acquired kidney injury in children.

METHODS

This non-systematic review summarizes recent evidence on APSGN. We discuss the epidemiology, pathogenesis, clinical and laboratory findings, histopathology, treatment and prognosis of the disease.

RESULTS

The median APSGN incidence in children in developing countries is estimated at 24.3/100,000 per year, compared with 6.2/100,000 per year in developed countries. Nephritis-associated plasmin receptor, identified as glyceraldehyde-3-phosphate dehydrogenase, and the cationic cysteine proteinase streptococcal pyrogenic exotoxin B are thought to be two leading streptococcal antigens involved in the pathogenesis of APSGN, which activate the complement system, mainly via the alternative but also the lectin pathway. This process is critical for the generation of inflammation by the ICs deposited in the glomerulus. The classic phenotype is an acute diffuse proliferative glomerulonephritis leading to features of the nephritic syndrome including hematuria, oliguria, hypertension and edema. The histopathology shows that the glomeruli are diffused affected, mostly presenting enlarged glomerular tuffs due to hypercellularity. Proliferative endothelial and mesangial cells and inflammation are also observed. APSGN frequently has spontaneous recovery. There is no specific therapy, but its morbidity and mortality are drastically reduced by the prevention and/or treatment of complications.

CONCLUSION

Despite recent advances, the pathogenesis of APSGN is not fully understood. There is no specific treatment for APSGN. The prognosis is generally good. However some cases may evolve to chronic kidney disease.

Acute glomerulonephritis

Glomerulonephritis is a heterogeneous group of disorders that present with a combination of haematuria, proteinuria, hypertension, and reduction in kidney function to a variable degree. Acute presentation with full blown nephritic syndrome or rapidly progressive glomerulonephritis is uncommon and is mainly restricted to patients with post-infectious glomerulonephritis, anti-neutrophil cytoplasmic antibodies-associated vasculitis, and anti-glomerular basement membrane disease. Most frequently, patients present with asymptomatic haematuria and proteinuria with or without reduced kidney function. All glomerulonephritis disorders can show periods of exacerbation, but disease flairs characteristically occur in patients with IgA nephropathy or C3 glomerulopathy. The gold standard for the diagnosis of a glomerulonephritis is a kidney biopsy, with a hallmark glomerular inflammation that translates into various histopathological patterns depending on the location and severity of the glomerular injury. Traditionally, glomerulonephritis was classified on the basis of the different histopathological patterns of injury. In the last few years, substantial progress has been made in unravelling the underlying causes and pathogenetic mechanisms of glomerulonephritis and a causal approach to the classification of glomerulonephritis is now favoured over a pattern-based approach. As such, glomerulonephritis can be broadly classified as immune-complex glomerulonephritis (including infection-related glomerulonephritis, IgA nephropathy, lupus nephritis, and cryoglobulinaemic glomerulonephritis), anti-neutrophil cytoplasmic antibodies-associated (pauci-immune) glomerulonephritis, anti-glomerular basement membrane glomerulonephritis, C3 glomerulopathy, and monoclonal immunoglobulin-associated glomerulonephritis. We provide an overview of the clinical presentation, pathology, and the current therapeutic approach of the main representative disorders in the spectrum of glomerulonephritis.

C3 Glomerulopathy: A Review with Emphasis on Ultrastructural Features

C3 glomerulopathy (C3G) is a rare disease resulting from dysregulation of the alternative complement pathway, resulting in the deposition of complement component 3 (C3) in the kidney. It encompasses two major subgroups: dense deposit disease and C3 glomerulonephritis (C3GN). Although the alternative complement pathway is typically a very tightly controlled system, dysregulation can be a result of genetic mutations in the fluid phase or membrane-bound inhibitors or accelerators. In addition, de novo/acquired autoantibodies against any of the regulatory proteins can alter complement activation either by negating an inhibitor or activating an accelerator. Triggering events can be complex; however, the final pathway is characterized by the uncontrolled deposition of C3 in glomeruli and the formation of the membrane attack complex. Light microscopic findings can be quite heterogeneous with a membranoproliferative pattern most commonly encountered. Diagnostic confirmation of C3G is based on a characteristic pattern of glomerular immunofluorescence staining, with C3-dominant deposits that are at least 2 orders of intensity greater than staining for any immunoglobulin (Ig) or C1q. Electron microscopy is necessary for diagnosing DDD in particular, but can also help to distinguish C3GN from other glomerular disease mimickers.

IgA-dominant infection-associated glomerulonephritis in the pediatric population

BACKGROUND

IgA-dominant infection-associated glomerulonephritis is well-documented in adults but has not been studied in depth in children. We assessed the incidence of pediatric IgA-dominant infection-associated glomerulonephritis and clinical and kidney biopsy findings.

METHODS

Pediatric native kidney biopsies over a 10-year period with IgA dominance, strong C3, and findings indicative of infection-associated etiology were identified.

RESULTS

We identified 9 cases of IgA-dominant infection-associated glomerulonephritis, 0.8% of pediatric native kidney biopsies. Seven patients presented with elevated creatinine. All had hematuria and proteinuria. Eight patients had clinical evidence of infection: one each with central port infection by methicillin-sensitive Staphylococcus aureus, recurrent streptococcal pharyngitis and recent otitis media, streptococcal pharyngitis demonstrated 8 months after biopsy, suspected streptococcal scalded skin syndrome, and viral gastroenteritis, and three with serologic evidence of Streptococcal infection but no identified site of infection. All but one patient experienced short-term normalization of creatinine and resolution of proteinuria, though two eventually progressed to kidney failure: one 3 years later due to progressive disease and one 11 years later due to focal segmental glomerulosclerosis without concurrent immune deposits.

CONCLUSIONS

Pediatric IgA-dominant infection-associated glomerulonephritis is rare, and generally has a favorable prognosis, contrasting that seen in adults with severe comorbidities. A higher resolution version of the Graphical abstract is available as Supplementary.

A case of acute poststreptococcal glomerulonephritis complicated by interstitial nephritis related to streptococcal pyrogenic exotoxin B

This paper presents the case of a patient who developed acute kidney injury and nephrotic syndrome following streptococcal cutaneous infection. He presented with microhematuria, severe proteinuria and systemic edema 5 days after infection. Blood examination showed elevated creatinine level, hypocomplementemia, and elevated anti-streptolysin O level. Renal biopsy revealed endocapillary proliferative glomerulonephritis with tubulointerstitial nephritis (TIN). Immunofluorescence revealed C3-dominant glomerular staining, while electron microscopy showed hump-shaped subepithelial deposits. The patient was therefore diagnosed with poststreptococcal glomerulonephritis. The unique histological feature was C3 deposition in the tubular basement membrane (TBM), in which we detected streptococcal pyrogenic exotoxin B (SpeB), a nephritogenic antigen produced by streptococci. No nephritis-associated plasmin receptor or plasmin activity was evident in the TBM. These nephritogenic antigens and upregulation of plasmin activity were observed in glomeruli. This case suggests that TIN after poststreptococcal infection might be partially attributable to SpeB toxicity.

Latency, Anti-Bacterial Resistance Pattern, and Bacterial Infection-Related Glomerulonephritis

BACKGROUND AND OBJECTIVES

Bacterial infection-related GN occurs concurrent to or after known or unknown infections. It is important to understand the clinical implications of the bacterial isolates, antimicrobial resistance patterns, and effect of latency-based classification on kidney and patient outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In total, 501 consecutive adults diagnosed with bacterial infection-related GN between 2005 and 2017 were included from a biopsy registry of 15,545 patients at a single center in South India, and follow-up data were collected from electronic medical records until December 2019. Latency was defined as time between resolution of infection and onset of GN, which was classified as parainfectious, peri-infectious, or postinfectious GN. Longitudinal kidney and patient outcomes were studied.

RESULTS

The mean age of the cohort was 40 (± 15) years, 6% were above 65 years, and 330 (66%) were men. Diabetes was present in 93 (19%) patients. Seventy percent (353 of 501) of patients had known infections, with the median latent period for parainfectious (115 of 353, 33%), peri-infectious (97 of 353, 27%), and postinfectious (141 of 353, 40%) GN being 0, 5 (4-7), and 15 (10-31) days, respectively. The most common predisposing organism was Streptococcus pyogenes (137 of 353, 39%). Drug-resistant nonstreptococcal bacteria were methicillin-resistant Staphylococcus aureus (25%, four of 16), extended-spectrum β-lactamases (20%, 12 of 59), and carbapenem-resistant organisms (10%, six of 59). Twenty of 22 (91%) of the drug-resistant organisms were isolated from the parainfectious group. The most common site of infection was skin in peri- (23 of 97, 24%) and postinfectious GN (61 of 141, 43%), and urinary tract in parainfectious GN (35 of 115, 30%). Of 321 patients with >3 months of follow-up, 48 (15%) developed kidney failure over a median period of 10 (2-37) months and 14 (4%) died. Parainfectious GN, eGFR<30 ml/min per 1.73 m², moderate-to-severe interstitial fibrosis and tubular atrophy, and nontreatment with renin-angiotensin system blockers were significant risk factors for progression to kidney failure by a Cox proportional-hazards model.

CONCLUSIONS

Along with clinical and histologic predictors, parainfectious GN caused predominantly by nonstreptococcal and drug-resistant bacterial infections was associated with poor kidney prognosis.

Introduction to Nephrocardiology

The interaction between nephrology and cardiovascular medicine is much broader than the cardiorenal syndrome. Many different aspects of cardiovascular medicine are interconnected with and substantially influenced by the conditions that fall into the realm of nephrology, and vice versa. Those aspects include pathophysiology, risk factors, epidemiology, prognosis, prevention, diagnosis, monitoring, and therapy. Discovery of the interconnected areas and development of appropriate knowledge and skill to optimally approach those circumstances can improve the quality of care and outcome of a large population of patients. Therefore, establishment of the distinct subspeciality of nephrocardiology is imperative.

Infection-Related Glomerulonephritis

Background

There has been a long, storied relationship between various bacterial infections and glomerular injury, which is now encompassed under the term of infection-related glomerulonephritis (GN). The clinical and pathologic manifestations vary depending on the duration, magnitude, and underlying pathogen associated with the inciting infectious process. A brief and acute episode may lead to a self-limiting glomerular manifestation while a chronic or repetitive infection can result in persistent and irreversible injury. In this review, we will discuss the clinical and pathologic findings associated with the infection-related glomerulonephritides.

Summary

An acute exudative GN with an influx of neutrophils is the most characteristic morphologic alteration associated with infection-related glomerular injury. The immunofluorescence staining pattern often reveals prominent complement component C3 deposition in both capillary walls and mesangial regions with or without accompanying immunoglobulin. Large subepithelial electron-dense deposits known as "humps" are the hallmark ultrastructural finding; however, these features can also be present in C3 glomerulopathies, which are often triggered by infections and may have similar underlying abnormalities in alternative pathway complement activation. In addition, other glomerular injuries can simultaneously be present along with infection-related GN, such as diabetic nephropathy, lupus nephritis, or immunoglobulin A nephropathy, constituting a true diagnostic challenge for the pathologist.

Key Messages

Bacterial infection-related GN represents a spectrum of glomerular injury with variable clinical and pathologic presentations. The pathologic findings can show overlap with other glomerular diseases, and different forms of infection-related GN vary in terms of prognosis and treatment approach.

Crescentic postinfectious glomerulonephritis in an adult patient with juvenile nasopharyngeal angiofibroma

Crescentic glomerulonephritis is usually associated with an acute nephritic syndrome with rapidly declining renal function. Postinfectious cases usually have a higher possibility of recovery. Juvenile nasopharyngeal angiofibroma (JNA) is a rare, locally aggressive tumour affecting mostly young men. A 28-year-old man presented with recurrent JNA initially excised 2 years prior. The patient was initially managed as a case of airway obstruction and pneumonia. He developed tea-coloured urine, oedema and acute kidney failure requiring dialysis while awaiting surgery. Urine and immunological studies (low C3, negative antineutrophil cytoplasmic antibody and antinucleosomal antibody and high antistreptolysin O) suggested a nephritic aetiology. Nasopharyngeal swab cultures of the mass revealed gram-negative organisms. Kidney biopsy showed diffuse proliferative glomerulonephritis compatible with a postinfectious glomerulonephritis with 77% cellular crescents. The mass was excised with histopathology consistent with JNA. The patient was eventually discharged off dialysis.

A man with immunoglobulin A nephropathy complicated by infection-related glomerulonephritis with glomerular depositions of nephritis-associated plasmin receptor

A 27-year-old man who developed heavy proteinuria with hematuria and acute kidney injury 2 weeks after a fever was referred to our hospital. Because he had low complements without autoantibodies, we clinically diagnosed him with infection-related glomerulonephritis. The proliferation of mesangial cells and endothelial cells with glomerular deposits of immunoglobulin A and complement 3 was found. Deposition of glomerular nephritis-associated plasmin receptor, a marker of infection-related glomerulonephritis, was also found. In addition, the distribution of nephritis-associated plasmin receptor deposition almost perfectly matched the plasmin activity-positive region. Over 3 months later, his symptoms were resolved, although moderate proteinuria and active urine sediment were persistent. He underwent a second renal biopsy, and the histological findings revealed that he had immunoglobulin A nephropathy. Therefore, we diagnosed him with infection-related glomerulonephritis superimposed on immunoglobulin A nephropathy at the first renal biopsy. The glomerular deposition of nephritis-associated plasmin receptor is a useful marker and may cause worsening urinalysis findings after bacterial infection in cases of chronic glomerulonephritis.

A Novel Glomerular C4d Scoring System: A Tool to Prognosticate Proliferative Exudative Pattern of Glomerular Injury

Aim:

Proliferative exudative pattern of glomerular injury is usually a manifestation of an infection related or a post-infectious glomerulonephritis (PIGN). Rarely, it may represent a C3 glomerulopathy, which is a dysfunction of the alternative pathway of complement activation, and is then termed an atypical PIGN (aPIGN). C4d deposits in the glomerulus are footprints of the classical and/or lectin pathway of complement activation and hence is expected to be positive in immune-mediated glomerulonephritis (GN) like classical infection-related GN, and could be used to differentiate classical PIGN from atypical PIGN.

Materials and Methods:

We report a novel C4d scoring system based on the intensity and the proportion of glomerular tuft staining, in a series of 104 biopsies with the proliferative exudative pattern of glomerular injury. Using a statistically derived cut-off score of 1.45, the cases were divided into C4d positive and C4d negative groups and compared to IF findings and the follow-up, available in 36 cases.

Results:

The C4d positive group had a significantly greater proportion of cases with immune complexes compared to the group with C3 deposits alone. In the follow-up, C4d negative group had also a greater number with partial/incomplete response compared to the C4d positive group.

Conclusions:

We recommend that the C4d stain be done in all cases with a proliferative exudative pattern of glomerular injury to identify patients who would need a close follow up and further assays of complement function.

Staphylococcus-induced glomerulonephritis: potential role for corticosteroids

Staphylococcus aureus is a troublesome pathogen, responsible for a broad range of clinical manifestations, ranging from benign skin infections to life-threatening conditions such as endocarditis and osteomyelitis. The kidney can be affected through a rapidly progressive glomerulonephritis mediated by an inflammatory reaction against a superantigen deposited in the glomerulus during the infection's course. This glomerulopathy has a poor prognosis, often leading to chronically impaired kidney function, eventually progressing to end-stage renal disease. Treatment rests on antibiotherapy. Despite the inflammatory role in this disease's pathophysiology, most authors discourage a simultaneous immunosuppressive approach given the concomitant infection. However, there are some reports of success after administration of systemic corticosteroids in these patients. We present a 66-year-old man with a staphylococcus-induced glomerulonephritis brought on by a vascular graft infection, with rapidly deteriorating kidney function despite extraction of the infected graft and 3 weeks of antibiotherapy with achievement of infection control. Kidney function improved after the introduction of corticosteroids. This case highlights the potential role of corticosteroids in selected cases of staphylococcus-induced glomerulonephritis, particularly those in which the infection is under control.

DNA methylation of FTO promotes renal inflammation by enhancing m6A of PPAR-α in alcohol-induced kidney injury

Alcohol consumption is one of the risk factors for kidney injury. The underlying mechanism of alcohol-induced kidney injury remains largely unknown. We previously found that the kidney in a mouse model of alcoholic kidney injury had severe inflammation. In this study, we found that the administration of alcohol was associated with the activation of NLRP3 inflammasomes and NF-κB signaling, and the production of pro-inflammatory cytokines. Whole-genome methylation sequencing (WGBS) showed that the DNA encoding fat mass and obesity-associated protein (FTO) was significantly methylated in the alcoholic kidney. This finding was confirmed with the bisulfite sequencing (BSP), which showed that alcohol increased DNA methylation of FTO in the kidney. Furthermore, inhibition of DNA methyltransferases (DNMTs) by 5-azacytidine (5-aza) reversed alcohol-induced kidney injury and decreased the mRNA and protein levels of FTO. Importantly, we found that FTO, the m6A demethylase, epigenetically modified peroxisome proliferator activated receptor-α (PPAR-α) in a YTH domain family 2 (YTHDF2)-dependent manner, which resulted in inflammation in alcoholic kidney injury models. In conclusion, our findings indicate that alcohol increases the methylation of PPAR-α m6A by FTO-mediated YTHDF2 epigenetic modification, which ultimately leads to the activation of NLRP3 inflammasomes and NF-κB-driven renal inflammation in the kidney. These findings may provide novel strategies for preventing and treating alcoholic kidney diseases.

Urinary sediments could differentiate endocapillary proliferative lupus nephritis and endocapillary proliferative IgA nephropathy

OBJECTIVE

This study investigated the differences in urinary sediment findings between patients with endocapillary proliferative lupus nephritis (LN) and patients with endocapillary proliferative IgA nephropathy (IgAN) and further evaluated the associations of leukocyturia with disease activity, pathological features and prognosis.

METHODS

The urinary sediments of 126 patients, including 92 with LN and 34 with IgAN, with renal-biopsy-proven endocapillary proliferative glomerulonephritis (EPGN) were examined by a standardized method. The urinary elements investigated included various cells, casts and crystals. The associations of leukocyturia with disease activity, pathological features and prognosis were further analyzed.

RESULTS

In the patients with EPGN, normal to mild leukocyturia (≤12/HPF) and moderate to severe leukocyturia (>12/HPF) were found in 52 (41.27%) and 74 (58.73%) patients, respectively. The proportion of moderate to severe leukocyturia and the frequencies of urinary white blood cell casts and waxy casts were significantly higher in endocapillary proliferative LN than those in endocapillary proliferative IgAN (P < 0.001, P = 0.020, P = 0.010, respectively). In the endocapillary proliferative LN group, the levels of leukocyturia were significantly correlated with serum creatinine (r = 0.288, P = 0.005), eGFR (r = -0.284, P = 0.006), serum C3 (r = -0.275, P = 0.009), SLEDAI scores (r = 0.383, P ≤ 0.001) and glomerular leukocyte infiltration (r = 0.285, P = 0.002). A multivariate analysis showed that leukocyturia was an independent risk factor for renal outcomes in endocapillary proliferative LN (HR: 1.456, 95% CI: 1.083-1.957, P = 0.013) but not in IgAN.

CONCLUSIONS

Urinary sediments of LN with EPGN and IgAN with EPGN differed in many aspects. Leukocyturia could reflect the disease activity and prognosis of EPGN, especially in endocapillary proliferative LN.

Disparate effects of methicillin-resistant Staphylococcus aureus infection on renal function in IgA-dominant infection-associated glomerulonephritis and menstrual toxic shock syndrome: a case report and literature review

The sudden outbreak of severe acute respiratory syndrome coronavirus 2 pneumonia posed a significant challenge to medical professionals because treatment of critically ill patients requires the efforts of a multidisciplinary team. To highlight this principle, we examined acute kidney injury (AKI) in IgA-dominant infection-associated glomerulonephritis (GN) and menstrual toxic shock syndrome (mTSS). Both GN and mTSS are rare diseases caused by staphylococcal infection, and renal function is frequently impaired. The resulting AKIs are disparate pathological entities driven by distinct immune mechanisms. We begin by describing the case of a diabetic man with pyopneumothorax following methicillin-resistant Staphylococcus aureus (MRSA). He had endocapillary proliferative GN with in situ IgA-dominant immune-complex formation in the mesangium accompanied by complement C3 deposition in the glomerular capillary wall. By contrast, acute tubular necrosis was observed in a case of mTSS; the patient's immune response was stimulated differently by MRSA enterotoxin and exotoxin resulting in aberrant IgA deposition, complement activation, and insufficient antibody production. As a multidisciplinary communication covering the fields of nephrology, immunology, and pathology, this report may help clinicians to understand these distinct renal lesions and make optimal therapeutic decisions expeditiously.

Asymptomatic sinusitis as an origin of infection-related glomerulonephritis manifesting steroid-resistant nephrotic syndrome: A case report

RATIONALE

Infection is a major trigger or pathogenic origin in a substantial proportion of glomerulonephritis (GN) patients, typically manifesting infection-related GN (IRGN). Various microorganisms, infection sites, and clinical and histopathological features are involved in IRGN. Once an infectious origin is identified and successfully eradicated, nephrotic syndrome or kidney dysfunction is spontaneously resolved. However, if patients are asymptomatic and the origin is undetermined, the diagnosis and treatment of GN is challenging. This case presentation reported on an IRGN case manifesting steroid-resistant nephrotic syndrome associated with asymptomatic sinusitis as a pathogenic origin.

PATIENT CONCERNS

A 68-year-old male presented with severe kidney dysfunction and edema in both extremities.

DIAGNOSIS

The patient was clinically diagnosed with hypocomplementemic nephrotic syndrome and kidney dysfunction and histopathologically with diffuse proliferative GN and a focal pattern of membranoproliferative GN. The findings suggested that idiopathic membranoproliferative glomerulonephritis type I was more likely than IRGN, given a critical lack of apparent infection.

INTERVENTIONS

Combined intravenous methylprednisolone, oral prednisolone, and cyclosporin did not improve the patient's condition. Thus, IRGN associated with inapparent infectious origin was suspected. Repeated thorough and careful examinations including CT scan showed sinusitis in his left maxillary sinus. Moreover, reanalysis of kidney specimen revealed positive nephritis-associated plasmin receptor in glomeruli, a typical finding for IRGN, supporting a pathogenic significance of his sinusitis. Medical treatment was initiated with 200 mg oral clarithromycin daily.

OUTCOMES

Oral clarithromycin gradually improved proteinuria and hypocomplementemia and resulted in nephrotic syndrome remission in parallel with opacification resolution of sinuses shown on CT.

LESSONS

This case presentation showed that asymptomatic sinusitis is potentially a pathogenic IRGN origin. A gold standard therapy for idiopathic GN, corticosteroid could be damaging in uncontrolled or underdiagnosed infection. In asymptomatic patients, a thorough screening of infectious diseases, including sinusitis, together with a renal histological evaluation of glomerular nephritis-associated plasmin receptor deposition is also essential in treating a wide spectrum of GN.

Postinfectious Glomerulonephritis

Postinfectious glomerulonephritis continues to be the most common cause of acute glomerulonephritis in children. Although in the past it was considered to be mainly a complication of streptococcal infections, today it is well known that infection with many other pathogens may trigger an immune response that results in glomerular injury. Most children with postinfectious glomerulonephritis have an excellent prognosis with complete recovery of renal function and no recurrence. This article summarizes the history, presentation, evaluation, differential diagnosis, and management of children with postinfectious glomerulonephritis. [Pediatr Ann. 2020;49(6):e273-e277.].

Clinicopathologic features of infection-related glomerulonephritis with IgA deposits: a French Nationwide study

Background

Infection-related glomerulonephritis with IgA deposits (IRGN-IgA) is a rare disease but it is increasingly reported in the literature. Data regarding epidemiology and outcome are lacking, especially in Europe. We aimed to assess the clinical, pathologic and outcome data of IRGN-IgA.

Methods

Clinical and outcome data from patients from 11 French centers over the 2007–2017 period were collected retrospectively. We reviewed pathologic patterns and immunofluorescence of renal biopsies and evaluated C4d expression in IRGN-IgA. We analyzed the correlation between histological presentation and outcome.

Results

Twenty-seven patients (23 men, mean age: 62 ± 15 years) were included. Twenty-one (78%) had Staphylococcus aureus infection and twelve (44%) were diabetic. At the time of biopsy, 95.2% had haematuria, 48.1% had a serum creatinine level of > 4 mg/dL, and 16% had hypocomplementemia. The most common pathologic presentation included mesangial (88.9%) and endocapillary proliferative glomerulonephritis (88.9%) with interstitial fibrosis and tubular atrophy (IF/TA) (85.1%). Diffuse and global glomerular C4d expression was found in 17.8%, mostly in biopsies with acute or subacute patterns, and was associated with a short delay between infection and renal biopsy compared to segmental and focal staining. After median follow-up of 13.2 months, 23.1% died, 46.2% had persistent renal dysfunction and 15.4% reached end-stage renal disease. Renal outcome was correlated to IF/TA severity.

Conclusions

Infection-related glomerulonephritis with IgA deposits is usually associated with Staphylococcus infections and mainly affects adult men. This entity has a poor prognosis which is correlated to interstitial fibrosis and tubular atrophy severity.