Staphylococcus-related glomerulonephritis and poststreptococcal glomerulonephritis: why defining "post" is important in understanding and treating infection-related glomerulonephritis

[Nephropathology of infectious disease]

Infections can affect the kidney via different pathways. Urinary tract infections can directly involve the renal tissue by spreading along pre-existing canalicular structures. Such an ascending infection can manifest as a highly active and purulent or even abscessing interstitial nephritis or as a chronic-fibrosing process in recurrent pyelonephritis. Viral infections can also use the canalicular route as in polyomavirus nephropathy or spread via the blood stream in a hematogenous manner as in the case of cytomegalovirus or hantavirus infections. Likewise, bacterial infections can reach the kidney via the blood in the case of systemic infection. Another large group of nephropathies taking place as a sequel of infections includes infection-related glomerulonephritides (IRGN), which are mediated by a series of immunological mechanisms. These IRGN can be subdivided according to their temporal association with the infectious process, occurring either after the infection has healed (postinfectious) or accompanying the ongoing infectious process (parainfectious). The latter, in particular, is of increasing importance in the daily practice of nephropathologists, especially in older patients. A number of other glomerulonephritis forms, i.e., membranous or membranoproliferative forms, can occur as a consequence of infection. In addition, infections can trigger nephropathies, such as thrombotic microangiopathy. The present article gives an overview of morphologic changes in renal parenchyma that take place as a consequence of infectious processes, with particular focus on IRGN.

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.

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.

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.

Acute Postinfectious Glomerulonephritis

Postinfectious glomerulonephritis (PIGN) is a leading cause of acute glomerulonephritis in children. The presentation of PIGN can vary from asymptomatic microscopic hematuria incidentally detected on routine urinalysis to nephritic syndrome and a rapidly progressive glomerulonephritis. Treatment involves supportive care with salt and water restriction, and the use of diuretic and/or antihypertensive medication, depending on the severity of fluid retention and the presence of hypertension. PIGN resolves completely and spontaneously in most children, and the long-term outcomes are typically good with preserved renal function and no recurrence.

Staphylococcus aureus-Associated Glomerulonephritis and Chronic Granulomatous Disease in an Adolescent Male

Staphylococcus-associated glomerulonephritis (GN) is an uncommon diagnosis in pediatric patients. Empiric therapy with steroids alone could potentially worsen the underlying infectious process in these patients, leading to worse clinical outcomes. An adolescent male diagnosed with GN was subsequently found to have chronic granulomatous disease with a Staphylococcus aureus liver abscess. His GN improved with antibiotics alone. This case illustrates the need to consider chronic infection, and primary immunodeficiency, in the differential diagnosis for new-onset GN.

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.

Long-Term Consequences of Puumala Hantavirus Infection

Several viral infections are associated with acute and long-term complications. During the past two years, there have been many reports on post-infectious symptoms of the patients suffering from COVID-19 disease. Serious complications occasionally occur during the acute phase of Puumala orthohantavirus caused nephropathia epidemica. Severe long-term consequences are rare. Fatigue for several weeks is quite common. Hormonal insufficiencies should be excluded if the patient does not recover normally.

Examining the Efficacy of Antimicrobial Therapy in Preventing the Development of Postinfectious Glomerulonephritis: A Systematic Review and Meta-Analysis

Postinfectious glomerulonephritis (PIGN) is an immune-mediated acute glomerulonephritis classically seen weeks after infection with Streptococcus pyogenes, although other infectious etiologies have emerged. While it has become increasingly rare in industrialized regions, it continues to affect children in developing countries. There has been debate as to why incidence rates are declining, including the possibility of improved initial treatment of bacterial infections. The ability of antimicrobial therapy in preventing PIGN as infectious sequelae, however, has not been comprehensively assessed. As varying evidence from published studies exists, the objective of this meta-analysis is to determine if antimicrobial therapy utilized to treat an initial infection has an effect in reducing the development of PIGN in humans. EMBASE, MEDLINE, and CENTRAL were searched using a comprehensive terminology strategy. From an initial search that returned 337 publications, 9 articles were included for analysis. Eight studies showed an incidence of PIGN after antimicrobial use ranging from 0.05% to 10% with a mean standardized difference (MSD) of 0.03 (0.01–0.06). Three studies showed an occurrence of PIGN without antibiotic use ranging from 1% to 13% with an MSD of 0.06 (−0.09–0.21). Our findings suggest that antimicrobial treatment for the initial infection may help diminish the development of PIGN. Although Streptococcus pyogenes infections are generally treated aggressively to prevent rheumatic fever, these findings may help further support the early treatment of bacterial infections to prevent postinfectious sequelae, especially as we consider other infectious etiologies of PIGN antimicrobial resistance.

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.

Treatment of the most common respiratory infections in children

Acute respiratory infections are the most common group of infective diseases in the pediatric population. Although the improvement of health care and vaccination program has led to a significant reduction in the incidence of certain respiratory infections, the combination of a high prevalence in vulnerable pediatric categories and uncritical prescription of antibiotics, due to the inability to adequately distinguish between viruses and bacterial etiology, still represents a significant challenge for the public health system. In order to promote rational antibiotic therapy with an overall improvement of both diagnostic and therapeutic principles, acute respiratory diseases have been the subject of consideration in numerous publications and national guidelines. Nonspecific clinical manifestations with pathogen heterogeneity and both anatomical and physiological characteristics of the child's respiratory system during growth and development have created the need for individualized therapy. Since the guidelines emphasize the undoubtful and crucial benefits of symptomatic therapy (e.g. analgesics in acute otitis media, supplemental oxygen in lower respiratory tract infections with hypoxemia), the use of antibiotics and corticosteroids is indicated in selected cases with a severe clinical picture. The choice of antibiotic depends on the clinical condition, presumed causative agent, and local epidemiologic circumstances. Respiratory support (oxygen therapy and/or artificial ventilation) is reserved for inpatient treatment of cases with a particularly severe clinical picture and associated complications.

Glomerulonephritides associated with infections

Glomerulonephritides associated with infections constitute an important group of diseases. Their occurrence is shifting from children and young people to elderly people. The rates of acute post-streptococcal glomerulonephritis, a condition with a good prognosis, are decreasing, and the rates of glomerulonephritides associated with various bacterial, viral, or parasitic infections, often with a poor prognosis, are increasing. Renal biopsy plays an important role in the diagnostic process. Manifestations of glomerulonephritis can be the initial sign of an occult infection. When evaluating renal biopsy specimens, certain signs may suggest this option, but it cannot be relied on completely. The search for an active infection is warranted in every patient with newly diagnosed glomerulonephritis. Hepatitis B and C serology is always performed, with other investigations depending on individual risk factors, clinical manifestations, and laboratory and histological findings. Failure to follow this rule may have serious consequences, in part because immunosuppressive therapy for glomerulonephritis can worsen the underlying infection and also because the progressive nature of parainfective glomerulonephritis cannot be reversed without eliminating the causative infection. Distinguishing between parainfective and autoimmune glomerulonephritis can be difficult, as there are no major differences in clinical manifestations, laboratory, and sometimes even histological findings. In the setting of the Czech Republic, important diseases include, in particular, staphylococcus infection-associated glomerulonephritis (SAGN) and, in general, infective endocarditis-associated glomerulonephritis, shunt nephritis, and other cases associated with foreign-material infection, such as catheters or electrodes. Among viral diseases, glomerulonephritides associated with the hepatitis B virus, hepatitis C virus, and the SARS CoV-2 virus are of major significance. The treatment of parainfectious glomerulonephritides involves elimination of the causative infection; only in rare cases, a combination of anti-infective treatment and mild immunosuppression can be indicated.

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.

Management of systemic risk factors ahead of dental implant therapy: A beard well lathered is half shaved

As the most successful therapy for missing teeth, dental implant has become increasingly prevalent around the world. A lot of papers have reported diverse local risk factors affecting the success and survival rate of dental implants, either for a short or a long period. However, there are also many types of systemic disorders or relatively administrated medicine that may jeopardize the security and success of dental implant treatment. Additionally, the coronavirus disease 2019 pandemic also poses a challenge to dental implant clinicians. Some of these risk factors are clinically common but to some extent unfamiliar to dentists, thus optimal measurements are often lacking when they occur in dental clinics. In this review, we analyze potential systemic risk factors that may affect the success rate of dental implants. Some of them may affect bone mineral density or enhance the likelihood of local infection, thus impeding osseointegration. Others may even systemically increase the risk of the surgery and threaten patients' life. In order to help novices receive high-risk patients who need to get dental implant treatment in a more reasonable way, we accordingly review recent research results and clinical experiments to discuss promising precautions, such as stopping drugs that impact bone mineral density or the operation, and addressing any perturbations on vital signs.

KM55 Monoclonal Antibody Staining in IgA-Dominant Infection-Related Glomerulonephritis

INTRODUCTION

IgA-dominant infection-related glomerulonephritis (IgA-IRGN) is a unique form of IRGN, which needs to be distinguished from IgA nephropathy (IgAN), due to overlapping clinical and pathological features. The key factor in the pathogenesis of IgAN is galactose-deficient IgA1 (Gd-IgA1). However, the mechanism of glomerular IgA deposition in patients with IgA-IRGN is unclear. Therefore, we evaluated whether Gd-IgA1 could be a useful biomarker to distinguish between these 2 diseases.

METHODS

A case-control study was conducted to analyze the clinical and pathological characteristics of 12 patients with IgA-IRGN. The intensity and distribution of glomerular Gd-IgA1 (KM55) staining in renal biopsies were assessed. The control group consisted of 15 patients diagnosed with IgAN and an additional 17 patients with glomerulopathy involving IgA deposition.

RESULTS

The main clinical manifestations of patients with IgA-IRGN were nephrotic-range proteinuria, hematuria, acute renal injury, and hypocomplementemia. Active lesions were the leading pathological feature, while focal segmental sclerosis was rare. Half of the patients exhibited hump-shaped subepithelial deposits. Glomerular KM55 staining was negative in 7 patients, trace in 4 patients, and 2+ in 1 patient. The median intensity of KM55 staining in IgA-IRGN patients was 0 (range 0∼2+), which was significantly lower than that of primary IgAN patients (median 2+, range 1+∼3+). The receiver operating characteristic analysis demonstrated that the optimal cutoff level to identify these 2 diseases was 0.5+.

CONCLUSIONS

Glomerular KM55 staining intensity might be helpful to distinguish IgA-IRGN from primary IgAN. Weak or negative staining may favor IgA-IRGN. In addition, integrated analysis including clinical data, pathological findings, and prognostic information would further improve the differential diagnosis.

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.

Atypical anti-glomerular basement membrane disease complicated by methicillin-susceptible Staphylococcus aureus infection-related rapidly progressive glomerulonephritis: a case report and literature review

Atypical anti-glomerular basement membrane (GBM) disease, which is characterized by low levels of or negativity for anti-GBM antibodies in circulation but positivity in the kidney, has been recognized in this decade. However, a therapeutic strategy has not been established to date because its outcome is better than that of classic anti-GBM disease. This case report and literature review highlight atypical anti-GBM disease in infection-related rapidly progressive glomerulonephritis. A 72-year-old Japanese man diagnosed with methicillin-susceptible Staphylococcus aureus (MSSA)-induced vertebral osteomyelitis experienced for 2 months was referred to our hospital because of renal insufficiency. He developed rapidly progressive glomerulonephritis with a serum creatinine level of 6.8 mg/dL, C-reactive protein level of 9.7 mg/dL, urinary protein-to-creatinine ratio of 3.37 g/gCr, and gross hematuria. The serum anti-GBM antibody concentration was 3.5 U/mL, which was slightly above the normal range (< 3.0 U/mL). Conservative treatment, mainly with antibiotics, improved the symptoms and renal function. The serum anti-GBM antibody concentration peaked at 4.0 U/mL on day 7 and decreased to an undetectable range at the end of eight-week antibiotic therapy. This is the first case report describing the presentation and disappearance of serum anti-GBM antibody in a patient with MSSA infection. Conservative treatment may be effective for patients with atypical anti-GBM disease complicated by infectious diseases.

Results of surgical management of infective endocarditis associated with Staphylococcus aureus

OBJECTIVES

Staphylococcus aureus (SA) is a leading cause of infective endocarditis (IE), and such cases are on the rise. Our objective was to evaluate the clinical outcomes of surgical intervention in patients with SA-associated IE and to identify the factors associated with outcomes.

METHODS

Between 2009 and 2017, 585 patients underwent valve surgery for definitive left-sided IE at 14 affiliated hospitals. Their medical records were retrospectively reviewed, and the preoperative variables and clinical results of patients with (n = 117) or without SA infection (n = 468) were compared.

RESULTS

The SA group had a more critical preoperative condition with higher rates of chronic haemodialysis, preoperative embolic events and preoperative inflammation levels, as well as worse renal function. In-hospital mortality was 20% and 7% in the patients with or without SA infection, respectively. The overall survival rate at 1 year and 5 years was 72% and 62% in the SA group, and 88% and 81% in the non-SA group, respectively (P < 0.001). The Cox hazard analysis revealed that methicillin-resistant SA infection was an independent risk factor for overall mortality in the SA group. The rate of freedom from recurrence of endocarditis at 1 year and 5 years was 95% and 90% in the SA group and 96% and 92% in the non-SA group, respectively (P = 0.43).

CONCLUSIONS

The short- and mid-term outcomes after valve surgery for active IE in patients with SA are still challenging. Methicillin-resistant SA infection is an independent predictor of mid-term mortality.

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.

Crescentic poststreptococcal acute glomerulonephritis accompanied by small vessel vasculitis: case report of an elderly male

Background

Poststreptococcal acute glomerulonephritis (PSAGN) in the elderly tends to have a severe clinical course and often presents with crescentic necrotizing glomerulonephritis in the renal biopsy. However, vasculitis lesions are unusual.

Case presentation

We present a 71-year-old man who was admitted to our hospital for a recurrent gout attack with a rapid decline of renal function. Low C3 levels and a high anti-streptolysin O titer were observed, while myeloperoxidase- and proteinase 3- antineutrophil cytoplasmic antibody (ANCA) were negative. In addition to cellular crescent and necrosis lesions, diffuse peritubular capillaritis and venulitis as well as small arteriole vasculitis in the glomerular hilus were also apparent. Although granular C3c deposits in the capillary wall and hump lesions were not found, immunofluorescent staining for nephritis-associated plasmin receptor (NAPlr) and in situ zymography for plasmin activity were both positive. We thus diagnosed PSAGN accompanied by small vessel vasculitis. Steroid therapy gradually improved the patient’s renal function, and hemodialysis was discontinued after 1 month.

Conclusions

In our case, streptococcus infection might have concurrently provoked vasculitis, and NAPlr staining was useful for confirming diagnosis.

Rare complications of Staphylococcus aureus infection in children: Case reports

Disseminated staphylococcal disease comprises a set of clinical manifestations secondary to multiple organ invasion that may range from cellulitis to sepsis. In pediatrics, the most common complications are osteoarticular and cutaneous infection; however, this article presents rare manifestations such as glomerulonephritis and thrombotic phenomena. This is the report of two cases of previously healthy adolescents: one presented with osteomyelitis and kidney injury, and the other, with lower limb cellulitis and respiratory deterioration with septic pulmonary embolism. The diagnostic process and additional management are described, highlighting the role of oxacillin in therapy. This article aims to highlight the importance of considering the rare manifestations of S. aureus infection, when the clinical evolution is abnormal, in order to initiate a timely treatment and get a better prognosis.

Epidemiology, pathogenesis, treatment and outcomes of infection-associated glomerulonephritis

For over a century, acute 'post-streptococcal glomerulonephritis' (APSGN) was the prototypical form of bacterial infection-associated glomerulonephritis, typically occurring after resolution of infection and a distinct infection-free latent period. Other less common forms of infection-associated glomerulonephritides resulted from persistent bacteraemia in association with subacute bacterial endocarditis and shunt nephritis. However, a major paradigm shift in the epidemiology and bacteriology of infection-associated glomerulonephritides has occurred over the past few decades. The incidence of APSGN has sharply declined in the Western world, whereas the number of Staphylococcus infection-associated glomerulonephritis (SAGN) cases increased owing to a surge in drug-resistant Staphylococcus aureus infections, both in the hospital and community settings. These Staphylococcus infections range from superficial skin infections to deep-seated invasive infections such as endocarditis, which is on the rise among young adults owing to the ongoing intravenous drug use epidemic. SAGN is markedly different from APSGN in terms of its demographic profile, temporal association with active infection and disease outcomes. The diagnosis and management of SAGN is challenging because of the lack of unique histological features, the frequently occult nature of the underlying infection and the older age and co-morbidities in the affected patients. The emergence of multi-drug-resistant bacterial strains further complicates patient treatment.

Infection-Induced Kidney Diseases

Infection induced kidney diseases are of concern for clinicians because timely detection and treatment of infections may cure or limit the extent of injury inflicted by microorganisms causing the infections. Infections can cause kidney injury by either direct invasion, or indirectly by immune mediated mechanisms, which manifest as post-infectious glomerulonephritis, or infection-related glomerulonephritis. Clinical manifestations may be acute or chronic depending on the microorganisms, endemic/epidemic nature and source of infection. All microbials virus, bacteria, mycobacteria, fungus, and protozoa have been implicated in kidney diseases either causing direct kidney injuries or immune-mediated injuries. Infection control practices in large parts of world is limited by poverty, social behavior, high population density, deforestation, inadequate access to safe drinking water, and poor health care facilities. Although, antimicrobials and vaccinations have successfully eradicated and cured many infectious diseases; however injudicious antimicrobial use and emergence of resistant organisms complicated the disease severity like secondary renal amyloidosis with chronic persistent infection. Re-emergence of various infections has been a recent pattern in developed world leading to uncertain diagnostic challenges, and association with kidney diseases.

Elderly patients with glomerular diseases and IgA nephropathy

As the population ages, greater numbers of elderly patients will present with kidney diseases. Many kidney diseases, such as IgA nephropathy, will require kidney biopsy for diagnostic confirmation, treatment guidance and prognostication. In this paper, we review the current and expected future healthcare landscape with a focus on the ageing population, pros and cons of kidney biopsy in elderly patients, as well as treatment strategies and precautions. We also review the available data on IgA nephropathy in the elderly, including its occurrence rate based on the kidney biopsy, clinicohistopathological features, differentiation with IgA-dominant postinfectious glomerulonephritis, treatment options and outcome prediction. Overall, information on kidney diseases in patients with advanced age, including IgA nephropathy, is limited. Clinical evaluation and management strategies are extrapolated largely from studies in younger adults. Age-specific clinical and translational investigations of kidney diseases are eminently needed.

Staphylococcus-Associated Glomerulonephritis Mimicking Henoch-Schönlein Purpura and Cryoglobulinemic Vasculitis in a Patient With an Epidural Abscess: A Case Report and Brief Review of the Literature

Rationale

Staphylococcus-associated glomerulonephritis (SAGN) is a rare immune complex-mediated glomerulonephritis associated with active Staphylococcus infection. We report a case illustrating the importance of clinical history and kidney biopsy findings in establishing the correct diagnosis.

Presenting concerns of the patient

We report the case of a 64-year-old man with alcohol-associated cirrhosis, type 2 diabetes mellitus, and hypertension who presented to hospital with lower back and abdominal pain, rectal bleeding, a purpuric lower extremity rash, and oliguric acute kidney injury with microscopic hematuria and nephrotic-range proteinuria.

Diagnoses

Skin biopsy revealed IgA leukocytoclastic vasculitis. Serum cryoglobulins were positive and there was hypocomplementemia with a low C3 level. Magnetic resonance imaging of the lumbar spine revealed septic discitis and epidural abscesses caused by a recent Staphylococcus aureus bacteremia. Kidney biopsy showed IgA-dominant and C3-dominant proliferative glomerulonephritis with subepithelial humps in keeping with SAGN.

Interventions

Urgent hemodialysis was initiated along with a prolonged course of intravenous cefazolin.

Outcomes

Remarkably, the patient demonstrated a complete recovery of renal function after 2 months of dialysis dependence and successful treatment of the epidural abscesses.

Lessons learned

This case shows that SAGN can closely mimic the clinical, laboratory, and histological presentation of Henoch-Schönlein Purpura or cryoglobulinemic vasculitis. Clinical history and kidney biopsy, particularly electron microscopic analysis, are essential to establishing the correct diagnosis to avoid the unnecessary and potentially harmful administration of immunosuppression. Despite the typically poor prognosis of SAGN, this case report illustrates that full renal recovery remains possible with supportive care and eradication of the underlying infection.

Staphylococcal Infection-Related Glomerulonephritis With Cryoglobulinemic Features

Introduction

Staphylococcal infection–related glomerulonephritis (GN) has been shown to represent a unique form of infection-related GN that contains IgA-dominant deposits and is often seen concurrently with the bacterial infection. Biopsies commonly reveal an endocapillary proliferative and/or exudative or mesangial proliferative GN. Rare cases have been reported to show cryoglobulin-like features, including hyaline pseudothrombi and wireloop deposits; however, detailed characterization of these cases is lacking.

Methods

The pathology archives from the University of Utah and Sharp Memorial Hospital were reviewed from January 2016 to September 2017 in search of cases with GN containing IgA-dominant deposits and features of cryoglobulinemia.

Results

Of 1965 native kidney biopsies, 5 showed IgA-dominant GN with cryoglobulinemic features. All patients had active staphylococcal infections at the time of biopsy. All presented with acute kidney injury (serum creatinine range: 1.7−6 mg/dl), and all had proteinuria and hematuria. All biopsies showed exudative GN, and 4 biopsies had focal crescents. All had focally prominent hyaline pseudothrombi with or without wireloop deposits, and all showed co-dominant staining for IgA and C3 on immunofluorescence microscopy. Serologic testing for cryoglobulinemia was performed in 3 patients and was transiently positive in 1 patient. Four patients required hemodialysis at last follow-up, whereas 1 patient returned to baseline kidney function.

Conclusion

IgA-dominant GN with cryoglobulinemic features is an uncommon but severe form of glomerular injury in patients with staphylococcal infections. Four of 5 patients had crescentic glomerular injuries, all of whom required hemodialysis at last follow-up. Patients with IgA-dominant GN with features of cryoglobulinemia should be evaluated for active staphylococcal infection.

Staphylococcus Infection-Associated Glomerulonephritis in a Kidney Transplant Patient: Case Report

BACKGROUND

Staphylococcus infection-associated glomerulonephritis is a rare cause of graft dysfunction in kidney transplant. Suspicion should be high in the setting of elevation of serum creatinine, active urinary sediment, with or without hypocomplementemia, and simultaneous Staphylococcus aureus infection. A kidney biopsy is usually diagnostic.

CASE REPORT

A 56-year-old man, who received a kidney transplant in 1998, with basal serum creatinine of 1.2 mg/dL and normal urinary sediment, was admitted to our kidney transplantation unit with graft dysfunction and a urinary tract infection caused by S aureus with septicemia, treated with antibiotics, in the context of recently intensified immunosuppression for a primary immune thrombocytopenia diagnosed 3 weeks earlier. After antibiotic treatment, the patient persisted with graft dysfunction, edema, and hypertension, with a S aureus isolation in the urine culture, active urinary sediment, and low C3. A kidney biopsy was performed, showing diffuse proliferative endocapillary and mesangial glomerulonephritis, with IgA(++) and C3(++) mesangial and endocapillary deposits in immunofluorescence. The patient was treated symptomatically and maintained his regular immunosuppression. At the last follow-up, his serum creatinine value was stable at 2.5 mg/dL.

CONCLUSIONS

The onset of a nephritic syndrome with a simultaneous S aureus infection should lead to suspicion of this uncommon entity, confirmed histologically. Despite its association with poor graft survival, our patient's graft survival remained stable.

[IgA nephropathy: Unusual forms]

IgA nephropathy can have various initial presentation and evolutive characteristics. In this article, specific forms of IgA nephropathy are described, such as hypertensive emergency, nephrotic syndrome, rapidly progressive glomerulonephritis, monotypic IgA deposits, or IgA nephropathy associated with inflammatory diseases. Identification of these specific forms is needed to better characterize and treat these rare pathologies.

Dominant C3 glomerulopathy: new roles for an old actor in renal pathology

Recently, a number of reports have described dominant C3 deposits in renal biopsies of patients with infection-related glomerulonephritis (GN). While acute post-infectious GN and membranoproliferative GN are commonly characterized by immune deposits containing C3 and/or C4, the absence of immunoglobulin (Ig) and/or immune complexes at light or electron microscopy is a rather unusual observation. Dominant C3 deposition is believed to result from the alternative pathway of complement activation via the C3bBb "tickover" convertase. The actual occurrence of C3 glomerulopathy could be underestimated, since infection-related GN often quickly subsides without the need for a renal biopsy. A more thorough understanding of the pathways that lead to complement assembly and deposition within the kidney is needed to support a new classification of complement-related lesions, including entities such as dense deposit disease, (atypical) hemolytic-uremic syndrome, dominant C1q, CFHR5, C4d, and C3 glomerulopathies. We will briefly review recent work in this area, focusing on GN with selective complement C3 deposits.

Analysis of clinical presentation, pathological spectra, treatment and outcomes of biopsy-proven acute postinfectious glomerulonephritis in adult indigenous people of the Northern Territory of Australia

AIM

Acute postinfectious glomerulonephritis is common in indigenous communities in the Northern Territory, Australia. It is a major risk factor for the high prevalence of chronic kidney disease. We aimed to analyse the clinical presentation, pathological spectra, treatment and outcomes of biopsy-proven acute postinfectious glomerulonephritis in the Northern Territory.

METHODS

We performed a retrospective cohort analysis of all adult patients (≥18 years) who were diagnosed with acute postinfectious glomerulonephritis on native renal biopsies from 01/01/2004 to 31/05/2014. The outcome measure was end-stage renal disease requiring long-term dialysis.

RESULTS

Forty-three of 340 patients who had renal biopsies had acute postinfectious glomerulonephritis. Most were Aboriginals (88.4%). They had co-morbidities; diabetes mellitus (60.5%), hypertension (60.5%) and smoking (56.4%). Forty-nine per cent had multiple pathologies on biopsy. Predominant histological pattern was diffuse proliferative glomerulonephritis (72%). Main sites of infections were skin (47.6%) and upper respiratory tract infection (26.2%) with streptococcus and staphylococcus as predominant organisms. Fifty per cent of patients developed end-stage renal disease. On multivariable logistic regression analysis, those on dialysis had higher baseline creatinine (P = 0.003), higher albumin/creatinine ratio at presentation (P = 0.023), higher serum creatinine at presentation (P = 0.02) and lower estimated glomerular filtration rate at presentation (P = 0.012).

CONCLUSION

Overall, most patients had pre-existing pathology with superimposed acute postinfectious glomerulonephritis that led to poor outcomes in our cohort.

Viral-Associated GN: Hepatitis B and Other Viral Infections

By definition, viral-associated GN indicates the direct pathogenic relationship between active viral replication and the development of acute GN. This definition is in sharp contrast to the semantic label and pathophysiologic foundation behind postinfectious GN that uniquely develops only during a period of resolved and absent active infection. The primary example of postinfectious GN are the glomerular lesions described after a pharyngeal or cutaneous streptococcal infection and do not represent the clinical or immunologic pattern seen with viral-associated GN. Hepatitis B (HBV) is the most common chronic viral infection in the world affecting >400 million people which is more than double the prevalence of chronic HIV and hepatitis C carriers combined. In addition, 10%-20% of HBV patients may be coinfected with hepatitis C and 5%-10% will have coinfection with HIV. Being able to distinguish the different types of GN seen with each viral infection is essential for the practicing clinician as each virus requires its own specific antiviral therapy. HBV-induced immune complex disease with renal injury lies on one end of the spectrum of disorders that occurs after a prolonged chronic carrier state. On the opposite end of the spectrum are renal diseases that develop from acute or subacute viral infections. One important glomerular lesion in this category is the association of collapsing FSGS with acute active cytomegalovirus, Epstein-Barr virus, and parvovirus B19 infection. The data supporting or disproving this relationship for each of these viruses will be discussed. A second renal manifestation of acute viral infections often occurs with many different sporadic or epidemic infections such as dengue and hantavirus and can lead to a transient proliferative GN that resolves upon viral clearance. The complex interplay of HBV and all viruses with the immune system provides conceptual lessons on the pathophysiology of immune complex GN that can be applied to all infection-related renal disease and plays an integral role in developing an approach to therapeutic intervention.

Staphylococcus Infection-Associated GN - Spectrum of IgA Staining and Prevalence of ANCA in a Single-Center Cohort

BACKGROUND AND OBJECTIVES

Staphylococcus infection-associated GN (SAGN) is a well recognized disease entity, particularly because of the frequent IgA-dominant glomerular immunoglobulin staining on kidney biopsy. Biopsy features can resemble two other disease entities - primary IgA nephropathy and Henoch-Schönlein purpura nephritis - posing a diagnostic pitfall. This is clinically relevant because of the crucial difference in the therapeutic approach. The diagnosis of SAGN is further complicated by the variability in the degree of glomerular IgA (and C3) staining, the extent of electron dense immune-type deposits, and positive ANCA serology in some patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a thorough histopathologic review of our single-center cohort of 78 culture-proven SAGN biopsies to assess the spectrum of IgA staining, prevalence of ANCA serology, prevalence of subepithelial "humps," and other histologic features to distinguish from primary IgA nephropathy.

RESULTS

Among the 78 SAGN biopsies, IgA staining was trace in 25%, mild in 19%, moderate in 44%, and strong in 12% of the cases. C3 was frequently moderate-to-strong but was trace in 14% of the biopsies. Concomitantly trace IgA, IgG, and C3 (pauci-immune pattern) was seen in 13%. Crescents were present in 35% of the SAGN biopsies. Out of 41 patients tested for ANCA, nine (22%) were positive, including patients with endocarditis and other infections. Subepithelial humps were identified in only 31% of the SAGN biopsies.

CONCLUSIONS

SAGN biopsies show marked variability in IgA immunofluorescence staining and low frequency of subepithelial humps compared with poststreptococcal GN. Occasional ANCA positivity is present in cases of SAGN, even in infections other than endocarditis. Therefore, biopsy diagnosis can be difficult particularly when clinical symptoms of infection are subtle. Both the pathologist and the nephrologist should be aware of these diagnostic pitfalls.

IgA-dominant Infection-related Glomerulonephritis in India: A Single-center Experience

IgA-dominant infection-related glomerulonephritis (IRGN) is a distinct morphologic variant of IRGN, characterized by dominant or codominant glomerular deposits of IgA, mostly in elderly and patients with diabetes. More cases are being reported in recent times due to increased awareness of the disease entity and increased rate of Staphylococcus infection. It usually presents as rapidly progressive renal failure with proteinuria, and treatment guidelines for this disease entity are not well defined. We report here 12 cases of IgA-dominant IRGN seen over a period of 5 years from a single center. Clinical features, biopsy findings, treatment, and outcomes were analyzed. Out of 12 patients, eight were males. The mean age of presentation was 52.4 ± 21 years. Skin was the most common site of infection seen in six patients. Gross hematuria was seen in 4 patients and 11 had nephrotic proteinuria. Eleven had low serum C3. Only two patients had diabetes. Methicillin-resistant Staphylococcus aureus (MRSA) was the most common organism isolated in six patients. Most common histopathology was crescentic glomerulonephritis seen in seven patients, followed by endocapillary proliferation in three and diffuse proliferative glomerulonephritis in two. Hemodialysis was done in eight patients and six patients received steroid therapy. End-stage renal disease developed in three patients, chronic kidney disease in three, and three patients died due to sepsis. Various infections including MRSA and Escherichia coli were associated with IgA-dominant IRGN both in patients with diabetes and nondiabetics. Suspicion and recognition of the disease is important as it has therapeutic and prognostic implications.

Nephrotic Syndrome without Hematuria due to Infection-Related Glomerulonephritis Mimicking Minimal-Change Disease in a Child

Nephrotic syndrome without hematuria due to infection-related glomerulonephritis is uncommon. The present report describes a case of nephrotic syndrome due to infection-related glomerulonephritis without hematuria and hypertension in an older child. A 14-year-old boy was referred to our hospital because of a 5-day history of fever, nausea, weight gain and recent leg edema without hypertension. Laboratory data showed nephrotic-range proteinuria, hypoalbuminemia, mild hypocomplementemia and acute renal injury without hematuria. Although, due to the clinical presentation, minimal-change nephrotic syndrome was mostly suspected, a renal biopsy showed endocapillary hypercellularity mainly of mononuclear cells with segmental mesangiolytic changes. Fine granular IgG and C3 deposits were noted by an immunofluorescent study; many relatively small electron-dense deposits were observed electron-microscopically. These findings led to the diagnosis of nephrotic syndrome due to infection-related endocapillary proliferative glomerulonephritis, although the causative organism of his nephritis was not detected. He recovered with rest and dietary cure. When we examine an acute nephrotic child, infection-related glomerulonephritis should be considered as the differential diagnosis to avoid unnecessary use of corticosteroids.

IgA nephropathy and infections

In this paper we concentrate on the role of infections in IgA nephropathy both from a pathogenetic and clinic point of view. The current hypotheses as regards the role of infections in the pathogenesis of IgA nephropathy are: (a) role of particular pathogens, (b) chronic exposure to mucosal infections, (c) abnormal handling of commensal microbes (gut microbiota). We also focus on particular infections reported in association with classic IgA nephropathy (HIV, malaria, Chlamydia, Lyme disease), as well as on IgA dominant-infection-associated glomerulonephritis. This is a unique form of glomerulonephritis, where IgA deposition is dominant. It is mostly recognized in old, diabetic patients and in association with staphylococcal infection.

Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN

Renal pathologists and nephrologists met on February 20, 2015 to establish an etiology/pathogenesis-based system for classification and diagnosis of GN, with a major aim of standardizing the kidney biopsy report of GN. On the basis of etiology/pathogenesis, GN is classified into the following five pathogenic types, each with specific disease entities: immune-complex GN, pauci-immune GN, antiglomerular basement membrane GN, monoclonal Ig GN, and C3 glomerulopathy. The pathogenesis-based classification forms the basis of the kidney biopsy report. To standardize the report, the diagnosis consists of a primary diagnosis and a secondary diagnosis. The primary diagnosis should include the disease entity/pathogenic type (if disease entity is not known) followed in order by pattern of injury (mixed patterns may be present); score/grade/class for disease entities, such as IgA nephropathy, lupus nephritis, and ANCA GN; and additional features as detailed herein. A pattern diagnosis as the sole primary diagnosis is not recommended. Secondary diagnoses should be reported separately and include coexisting lesions that do not form the primary diagnosis. Guidelines for the report format, light microscopy, immunofluorescence microscopy, electron microscopy, and ancillary studies are also provided. In summary, this consensus report emphasizes a pathogenesis-based classification of GN and provides guidelines for the standardized reporting of GN.

Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN

Renal pathologists and nephrologists met on February 20, 2015 to establish an etiology/pathogenesis-based system for classification and diagnosis of GN, with a major aim of standardizing the kidney biopsy report of GN. On the basis of etiology/pathogenesis, GN is classified into the following five pathogenic types, each with specific disease entities: immune-complex GN, pauci-immune GN, antiglomerular basement membrane GN, monoclonal Ig GN, and C3 glomerulopathy. The pathogenesis-based classification forms the basis of the kidney biopsy report. To standardize the report, the diagnosis consists of a primary diagnosis and a secondary diagnosis. The primary diagnosis should include the disease entity/pathogenic type (if disease entity is not known) followed in order by pattern of injury (mixed patterns may be present); score/grade/class for disease entities, such as IgA nephropathy, lupus nephritis, and ANCA GN; and additional features as detailed herein. A pattern diagnosis as the sole primary diagnosis is not recommended. Secondary diagnoses should be reported separately and include coexisting lesions that do not form the primary diagnosis. Guidelines for the report format, light microscopy, immunofluorescence microscopy, electron microscopy, and ancillary studies are also provided. In summary, this consensus report emphasizes a pathogenesis-based classification of GN and provides guidelines for the standardized reporting of GN.