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

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.

[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.

Suitability of reduced dose glucocorticoids therapy regimen for antibody-associated vasculitis patients with TB: a retrospective study

INTENTION

Immunosuppressive therapy is the major treatment approach for patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). Due to impaired cellular immunological function and the use of glucocorticoids and immunosuppressants, AAV patients are predisposed to opportunistic infections, including tuberculosis (TB). This retrospective study aims to analyze the clinical characteristics of patients with AAV and TB and explore suitable glucocorticoid regimens for them. So as to provide a basis for future clinical guidelines and have important value for guiding clinical treatment.

METHODS

This study retrospectively reviewed 58 AAV patients (18-80 years old) with TB admitted to Changsha Central Hospital Affiliated with the University of South China from 2016.1 to 2023.4 Patients were divided into standard-dose and reduced-dose glucocorticoid groups before retrospectively analyzing their medical records.

RESULTS

A total of 58 AAV patients with TB were enrolled, with 15 dying throughout the monitoring period. Through analysis data, compared with the standard-dose group, the reduced group had less proteinuria and hematuria. In survival analysis, the reduced-dose glucocorticoid group had lower mortality than the standard-dose group (P = 0.03); however, no significant difference was noted in the use of immunoglobulin (P = 0.39), tuberculosis activity (P = 0.64), and age stratification (P = 0.40). The BVAS score before treatment and 6 months post-treatment suggest that the two regimens cause the same risk of ESKD (P > 0.05).

CONCLUSION

In conclusion, the reduced glucocorticoid dose group can achieve the same curative effect as the standard dose group and has less damage to the kidney in hematuria and proteinuria. Therefore, the reduced glucocorticoid dose treatment regimen may be more suitable for AAV patients with TB.

Clinicopathological differences between Bartonella and other bacterial endocarditis-related glomerulonephritis - our experience and a pooled analysis

Background

Although Staphylococcus aureus is the leading cause of acute infective endocarditis (IE) in adults, Bartonella spp. has concomitantly emerged as the leading cause of "blood culture-negative IE" (BCNE). Pre-disposing factors, clinical presentation and kidney biopsy findings in Bartonella IE-associated glomerulonephritis (GN) show subtle differences and some unique features relative to other bacterial infection-related GNs. We highlight these features along with key diagnostic clues and management approach in Bartonella IE-associated GN.

Methods

We conducted a pooled analysis of 89 cases of Bartonella IE-associated GN (54 published case reports and case series; 18 published conference abstracts identified using an English literature search of several commonly used literature search modalities); and four unpublished cases from our institution.

Results

Bartonella henselae and Bartonella quintana are the most commonly implicated species causing IE in humans. Subacute presentation, affecting damaged native and/or prosthetic heart valves, high titer anti-neutrophil cytoplasmic antibodies (ANCA), mainly proteinase-3 (PR-3) specificity, fastidious nature and lack of positive blood cultures of these Gram-negative bacilli, a higher frequency of focal glomerular crescents compared to other bacterial infection-related GNs are some of the salient features of Bartonella IE-associated GN. C3-dominant, but frequent C1q and IgM immunofluorescence staining is seen on biopsy. A "full-house" immunofluorescence staining pattern is also described but can be seen in IE -associated GN due to other bacteria as well. Non-specific generalized symptoms, cytopenia, heart failure and other organ damage due to embolic phenomena are the highlights on clinical presentation needing a multi-disciplinary approach for management. Awareness of the updated modified Duke criteria for IE, a high index of suspicion for underlying infection despite negative microbiologic cultures, history of exposure to animals, particularly infected cats, and use of send-out serologic tests for Bartonella spp. early in the course of management can help in early diagnosis and initiation of appropriate treatment.

Conclusion

Diagnosis of IE-associated GN can be challenging particularly with BCNE. The number of Bartonella IE-associated GN cases in a single institution tends to be less than IE due to gram positive cocci, however Bartonella is currently the leading cause of BCNE. We provide a much-needed discussion on this topic.

Immunofluorescence Use and Techniques in Glomerular Diseases: A Review

Background

Immunofluorescence (IF) studies play an essential role in the evaluation of medical renal biopsies. Particularly, in the study of renal glomerular diseases, where it provides fundamental data for the diagnosis, classification, and etiology of the glomerular pathologies. Diverse techniques may be used to optimize the utilization of IF studies, from variations on the test methodologies to expertise on the interpretation of the results and knowledge of potential pitfalls.

Summary

This manuscript presents a brief review on the history of IF and its utilization in kidney pathology, followed by a description of the IF methods, including the use of IF on paraffin-embedded tissue (paraffin IF), and other novel techniques. Guidelines on how to best report IF findings are reviewed, along with a description of antibodies commonly used in glomerular diseases, highlighting their distribution within the normal kidney and potential pitfalls in interpretation. Finally, the use and interpretation of IF are discussed in more detail in individual entities on a range of glomerular diseases.

Key Messages

IF is crucial for interpretation of renal biopsies and diagnosis of glomerular diseases. Knowledge of IF techniques, alternative procedures, its use and proper interpretation is essential for optimal utilization of IF in renal pathology, and this review proposes to serve as a simplified and practical guide on this topic.

Treatment of IgA Nephropathy: A Rapidly Evolving Field

The pivotal event in the pathophysiology of IgA nephropathy is the binding of circulating IgA-containing immune complexes to mesangial cells, with secondary glomerular and tubulointerstitial inflammation and fibrosis. The paramount difficulty in the management of IgA nephropathy is the heterogeneity in its clinical presentation and prognosis, requiring an individualized treatment approach. Goal-directed supportive care remains the bedrock of therapy for all patients, regardless of risk of progression. Sodium-glucose transporter 2 inhibitors and sparsentan should be integral to contemporary supportive care, particularly in patients with chronic kidney damage. Pending the development of reliable biomarkers, it remains a challenge to identify patients prone to progression due to active disease and most likely to derive a net benefit from immunosuppression. The use of clinical parameters, including the degree of proteinuria, the presence of persistent microscopic hematuria, and the rate of eGFR loss, combined with the mesangial hypercellularity, endocapillary hypercellularity, segmental glomerulosclerosis, tubular atrophy/interstitial fibrosis, crescents score, is currently the best approach. Systemic glucocorticoids are indicated in high-risk patients, but the beneficial effects wane after withdrawal and come at the price of substantial treatment-associated toxicity. Therapies with direct effect on disease pathogenesis are increasingly becoming available. While targeted-release budesonide has garnered the most attention, anti-B-cell strategies and selective complement inhibition will most likely prove their added value. We propose a comprehensive approach that tackles the different targets in the pathophysiology of IgA nephropathy according to their relevance in the individual patient.

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.

Targeted Transcriptional Analysis of IgA Vasculitis, IgA Nephropathy, and IgA-Dominant Infection-Related Glomerulonephritis Reveals Both Distinct and Overlapping Immune Signatures

Key Points

Skin IL-9, calprotectin, and KIR gene expression may be predictive of subsequent kidney involvement in patients with IgAV. Histologically similar patients with IgAN, IgAV, and IgA-IRGN can be distinguished by their immune transcriptomes. Kidney biopsies from patients with IgA-IRGN are enriched for transcripts involved in granulocyte chemotaxis.

Background

IgA vasculitis (IgAV), IgA nephropathy (IgAN), and IgA-dominant infection-related glomerulonephritis (IgA-IRGN) have shared histopathologic features, but differences in clinical management and prognosis. The most serious IgAV organ involvement is in the kidneys (IgAV nephritis). In this study, we hypothesized that targeted immune transcript profiling could aid in (1 ) predicting the development of IgAV nephritis in patients with cutaneous IgAV and (2 ) differentiating IgAN, IgAV, and IgA-IRGN.

Methods

RNA was extracted from 24 formalin-fixed paraffin-embedded tissue specimens (16 kidney, 8 skin) from 21 patients with IgAV nephritis (n=7), IgAN (n=5), and IgA-IRGN (n=4), and IgAV skin biopsies from patients with (n=3) and without (n=5) IgAV nephritis. Differential gene expression and gene set enrichment analysis were performed on a total of 594 transcripts (Nanostring immunology panel) profiled using the nCounter system.

Results

Skin biopsies in patients with IgAV who develop kidney involvement exhibit reduced S100A8/S100A9 , IL9 , and killer cell immunoglobulin-like receptor expression. The kidney tissue immune transcriptomes of IgAN, IgAV, and IgA-IRGN are largely overlapping. IgA-IRGN kidney biopsies are, however, uniquely enriched for transcripts involved in granulocyte chemotaxis.

Conclusion

This study identifies immune transcript signatures that may predict IgAV nephritis in skin biopsies and distinguish IgA-IRGN from IgAN and IgAV in kidney biopsies.

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.

A rare case of Immunoglobulin A dominant post-infectious glomerulonephritis (IgA PIGN) in a young patient

Background

Immunoglobulin A dominant postinfectious glomerulonephritis (IgA PIGN) is a unique medical entity that is rare in the paediatric population. It usually presents with severe renal failure, heavy proteinuria, hypertension, and hypocomplementemia and frequently has an unfavourable prognosis. IgA PIGN generally occurs in association with staphylococcal infections and diabetes mellitus in adult patients. Other pathogens include Escherichia coli and Streptococcus sp. Immunofluorescence studies of kidney biopsy samples show IgA as dominant or codominant antibody.

Case presentation

We encountered a 3-year-old girl with IgA PIGN presenting with acute renal failure, oedema, hypertension, and heavy proteinuria of 7955 mg/g creatinine. Renal biopsy specimens showed diffuse glomerular endocapillary hypercellularity with prominent neutrophil and monocyte infiltration on light microscopy. Strong deposits of IgA and C₃ were observed along the glomerular basement membranes and the mesangium by immunofluorescence microscopy, and electron microscopy revealed the presence of subepithelial humps.

The patient was managed with steroid (and probatory antibiotic) therapy and is now undergoing follow-up, with a significant improvement 6 months after the initial presentation (glomerular filtration rate (GFR) and cystatin C clearance rate of 165 ml/min/1.73m² and 106 ml/min/1.73m², respectively). No signs of bacterial infection were detectable.

Conclusion

This variant of IgA PIGN must be distinguished from other clinical entities, especially IgA nephropathy (mesangial IgA deposits) and postinfectious glomerulonephritis (C3, IgG and occasional IgM capillary loop deposits with or without mesangial distribution), since patients with IgA PIGN may require steroid treatment in addition to antibiotic therapy. Differential diagnosis should also include C₃ glomerulopathy.

IgA PIGN is a recently identified disease entity that generally manifests in adult patients with both IgA and C3 mesangial and glomerular capillary wall deposits. We present a biopsy-proven case of IgA PIGN that manifested in a patient at an exceptionally young age and that has had a good clinical outcome. To the best of our knowledge, this is the youngest IgA PIGN patient reported thus far.

Antineutrophil cytoplasmic antibodies in infective endocarditis: a case report and systematic review of the literature

Infective endocarditis (IE) may be misdiagnosed as ANCA-associated vasculitis (AAV), especially when antineutrophil cytoplasmic antibodies (ANCA) are detected. Distinguishing IE from AAV is crucial to guide therapy. However, little is known about ANCA positivity in IE patients. We present a case report and systematic review of the literature on patients with ANCA-positive IE, aiming to provide a comprehensive overview of this entity and to aid clinicians in their decisions when encountering a similar case. A systematic review of papers on original cases of ANCA-positive IE without a previous diagnosis of AAV was conducted on PubMed in accordance with PRISMA-IPD guidelines. A predefined set of clinical, laboratory, and kidney biopsy findings was extracted for each patient and presented as a narrative and quantitative synthesis. A total of 74 reports describing 181 patients with ANCA-positive IE were included (a total of 182 cases including our own case). ANCA positivity was found in 18-43% of patients with IE. Patients usually presented with subacute IE (73%) and had positive cytoplasmic ANCA-staining or anti-proteinase-3 antibodies (79%). Kidney function was impaired in 72%; kidney biopsy findings were suggestive of immune complexes in 59%, while showing pauci-immune glomerulonephritis in 37%. All were treated with antibiotics; 39% of patients also received immunosuppressants. During follow-up, 69% of patients became ANCA-negative and no diagnosis of systemic vasculitis was reported. This study reviewed the largest series of patients with ANCA-positive IE thus far and shows the overlap in clinical manifestations between IE and AAV. We therefore emphasize that clinicians should be alert to the possibility of an underlying infection when treating a patient with suspected AAV, even when reassured by ANCA positivity. Key Points • This systematic review describes - to our knowledge - the largest series of patients with ANCA-positive infective endocarditis (IE) thus far (N=182), and shows a high degree of overlap in clinical manifestations between IE and ANCA-associated vasculitis (AAV). • ANCA positivity was found in 18-43% of patients with infective endocarditis. Of patients with ANCA-positive IE, the majority (79%) showed cytoplasmic ANCA-staining or anti-PR3-antibodies. We emphasize that clinicians should be alert to the possibility of an underlying infection when treating a patient with suspected AAV, even when reassured by ANCA positivity. • In patients with IE and ANCA-associated symptoms such as acute kidney injury, an important clinical challenge is the initiation of immunosuppressive therapy. All patients with data in this series received antibiotics; 39% also received immunosuppressive therapy. In many of these patients, ANCA-associated symptoms resolved or stabilized after infection was treated. ANCA titers became negative in 69% , and a diagnosis of AAV was made in none of the cases. We therefore recommend that (empiric) antibiotic treatment remains the therapeutic cornerstone for ANCA-positive IE patients, while a watchful wait-and-see approach with respect to immunosuppression is advised.

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.

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 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.

A Case of Immunoglobulin A (IgA)-Dominant Infection-Related Glomerulonephritis Treated With Plasmapheresis

Immunoglobulin A (IgA)-dominant infection-related glomerulonephritis (IRGN) is mostly associated with Staphylococcal or other bacterial infections like Streptococcus and Gram-negative bacilli. Antibiotics are the cornerstone of treatment in these cases. When the bacterial infection can’t be recognized or IRGN persists despite treating the underlying infection, controlling the kidney injury becomes cumbersome and lacks a strong evidence-based approach. In this report, we describe a 38-year-old male patient with a history of polysubstance abuse and chronic hepatitis B and hepatitis C infections who presented with acute kidney injury and nephrotic syndrome due to IgA-dominant IRGN without an active concurrent bacterial infection who responded well to plasmapheresis.

Renal autoimmunity: The role of bacterial and viral infections, an extensive review

Autoimmunity is a process by which the loss of self-tolerance results in an immune attack against the body own tissues and organs. For autoimmunity to occur, various elements serving as triggers were described by which infections are considered one of the leading factors. In turn, renal involvement in autoimmune diseases, whether by an organ-specific attack, or as part of a systemic disease process, is well known. As bacterial and viral infections are considered to be common triggers for autoimmunity in general, we aimed to study their association with renal autoimmunity in particular. We performed an extensive search of the recent and relevant medical literature regarding renal autoimmunity syndromes such as infection-associated glomerulonephritis and vasculitis, associated with bacterial and viral infections. By utilizing PubMed and Google Scholar search engines, over 200 articles and case reports were reviewed. Among other mechanisms, direct infection of the renal parenchyma, molecular mimicry, induction of B-cells or secretion of superantigens, bacterial and viral pathogens were found to correlate with the development of renal autoimmunity. Nevertheless, this was not true for all pathogens, as some mimic autoimmune diseases and others show a surprisingly protective effect. The exact immunopathogenesis is yet to be determined, however. For conclusion, bacterial and viral infections are linked to renal autoimmunity by both direct damage and as mediators of systemic diseases. Further research particularly on the immunopathogenetic mechanisms of renal autoimmunity associated with infections is required.

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.

Glomerular IgA Deposition and Serum Antineutrophil Cytoplasmic Antibody Positivity in a Child With Dystrophic Epidermolysis Bullosa: Case Report and Literature Review

Patients with epidermolysis bullosa (EB) could develop significant urological complications, such as hydroureteronephrosis, renal amyloidosis and IgA nephropathy (IgAN). Here, we presented a 12-year-old boy carrying pathogenic COL7A1 mutation with diagnosis of dystrophic epidermolysis bullosa (DEB). The patient had concomitant gross hematuria and proteinuria. Pathological examinations and immunostaining of renal biopsy showed glomeruli with mesangial hypercellularity and deposition of IgA, which were indicative of IgAN. Interestingly, serological evaluation showed antineutrophil cytoplasmic antibody (ANCA) directed against myeloperoxidase and proteinase 3. Treatment with glucocorticoid, immunosuppressants, angiotensin-converting enzyme inhibitor and antibiotics efficiently improved hemato-proteinuria, and ANCAs became negative as well. This case of DEB presented a unique collection of clinical manifestations and pathological alterations. IgAN and serum positive ANCA were possibly associated with sustained infection secondary to DEB, and can be managed by empirical treatment for primary IgAN.

Infective Endocarditis-Associated Purpura and Glomerulonephritis Mimicking IgA Vasculitis: A Diagnostic Pitfall

BACKGROUND

Purpura and glomerulonephritis are typical presentations in IgA vasculitis. Infective endocarditis mimicking IgA vasculitis by presenting with glomerulonephritis and purpura is rarely reported.

METHODS

We searched for cases with infective endocarditis-associated purpura and glomerulonephritis in a tertiary hospital in China and retrospectively reviewed their clinicopathological features. Differential diagnosis and treatment in patients with infective endocarditis-associated purpura and glomerulonephritis were discussed.

RESULTS

A total of 20 cases with infective endocarditis-associated purpura and glomerulonephritis were identified among 548 cases with infective endocarditis in our center during an 8-year period: 7 of the 20 cases (35%) were initially misdiagnosed as IgA vasculitis and 10 cases (50%) presented with left-sided endocarditis caused by Streptococcus viridans. Fever (100%, 20 out of 20), prior valvular deformities (80%, 16 out of 20), cardiac murmur (95%, 19 out of 20), splenomegaly (84%, 16 out of 19), embolism (55%, 11 out of 20), and hypocomplementemia (76%, 13 out of 17) were present in most patients. Crescents and mesangial hypercellularity with or without endothelial hypercellularity were the primary findings on light microscopy, with C3-dominant deposition on immunofluorescence. But IgA-dominant staining was also observed (40%, 2 out of 5). In patients with rapidly progressive glomerulonephritis, patients with complete recovery of renal function had shorter disease duration and higher ratio (67% vs 20%) of immunosuppressive therapy compared with patients with partial recovery.

CONCLUSIONS

Infective endocarditis-associated glomerulonephritis and purpura can closely mimic IgA vasculitis. Differential diagnosis is challenging, particularly when typical presentations of infective endocarditis are absent. In adults with presentations like IgA vasculitis, infective endocarditis should be evaluated through comprehensive clinical and pathological investigations. Immunosuppressive therapy can be considered in patients with severe glomerulonephritis who do not improve after proper anti-infective therapy.

IgA nephropathy in patients with serum anti-neutrophil cytoplasmic autoantibody (ANCA) positivity: case series

Some cases of patients with IgA nephropathy diagnosed via kidney biopsy and antineutrophil cytoplasmic antibody (ANCA) positivity have been reported. This article describes a case series comprising patients with IgA nephropathy and ANCA positivity seen at a medical center in the city of São Paulo, Brazil, from 1996 to 2016. A total of 111 patients underwent diagnostic kidney biopsies for IgA nephropathy. Five were ANCA-positive at the time of diagnosis; their mean age was 45 ± 15.3 years and they were predominantly females with a mean proteinuria of 2.2 ± 0.9 g/day and a median serum creatinine level of 2.5 (2.0 - 8,6) mg/dL; all had hematuria. Four of the five were cANCA-positive (80%); all had normal serum C3 and C4 levels; and 80% were positive for ANA. One case presented an association with infection, but no associations were found with medication. One patient had granuloma and another had a collapsing lesion. This article describes the cases of five ANCA-positive patients (with predominantly cANCA positivity) submitted to diagnostic kidney biopsies for IgA nephropathy; one patient had a collapsing lesion, but progressed well.

The Continuing Need for Electron Microscopy in Examination of Medical Renal Biopsies: Examples in Practice

Background

For the better part of the past 6 decades, transmission electron microscopy (EM), together with routine light microscopy and immunofluorescence and/or immunohistochemistry (IHC), has been an essential component of the diagnostic workup of medical renal biopsies, particularly native renal biopsies, with increasing frequency in renal allograft biopsies as well. Studies performed prior to the year 2000 have indeed shown that a substantial fraction of renal biopsies cannot be accurately diagnosed without EM. Still, EM remains costly and labor-intensive, and with increasing pressure to reduce healthcare costs, some centers are de-emphasizing diagnostic EM. This trend has been coupled with advances in IHC and other methods in renal biopsy diagnosis over the past 2-3 decades.

Summary

Nonetheless, it has been our experience that the diagnostic value of EM in the comprehensive evaluation of renal biopsies remains similar to what it was 20-30 years ago. In this review, we provide several key examples from our practice where EM was essential in making the correct renal biopsy diagnosis, ranging from relatively common glomerular lesions to rare diseases.

Key Messages

EM remains an important component of the diagnostic evaluation of medical renal biopsies. Failure to perform EM in certain cases will result in an incorrect diagnosis, with possible clinical consequences. We strongly recommend that tissue for EM be taken and stored in an appropriate fixative and ultrastructural studies be performed for all native renal biopsies, as well as appropriate renal allograft biopsies as recommended by the Banff consortium.

ANCA-Associated Vasculitis: An Update

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) represents a group of small vessel vasculitides characterized by granulomatous and neutrophilic tissue inflammation, often associated with the production of antibodies that target neutrophil antigens. The two major antigens targeted by ANCAs are leukocyte proteinase 3 (PR3) and myeloperoxidase (MPO). AAV can be classified into 3 categories based on patterns of clinical involvement: namely, granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic GPA (EGPA). Clinically, AAV involves many organ systems including the lungs, kidneys, skin, and nervous system. The prognosis of AAV has improved dramatically due to advances in the understanding of its pathogenesis and treatment modalities. This review will highlight some of the recent updates in our understanding of the pathogenesis, clinical manifestations, and treatment options in patients with AAV focusing on kidney involvement.

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.

A Curious Case of Acute Glomerulonephritis - Staphylococcus vs Lupus: Case Report and Literature Review

Here we report a case of a 65-year-old female, where we encountered acute glomerulonephritis. The patient initially presented with a hemorrhagic blister involving the second through fourth toes with serosanguinous discharge and was on hydralazine for blood pressure control. Differentials included Staphylococcus-associated/lupus nephritis/anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis. Still, detailed history and meticulous clinical approach with supporting labs and imaging helped us to narrow it to Staphylococcus-associated glomerulonephritis, which is rarely encountered in clinical practice and is associated with high mortality. The management of the patient resulted in a positive outcome and she was discharged home. 

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.

Factors Affecting the Progression of Infection-Related Glomerulonephritis to Chronic Kidney Disease

Acute glomerulonephritis (AGN) triggered by infection is still one of the major causes of acute kidney injury. During the previous two decades, there has been a major paradigm shift in the epidemiology of AGN. The incidence of poststreptococcal acute glomerulonephritis (PSAGN), which develops after the cure of group A Streptococcus infection in children has decreased, whereas adult AGN cases have been increasing, and those associated with nonstreptococcal infections, particularly infections by Staphylococcus, are now as common as PSAGN. In adult AGN patients, particularly older patients with comorbidities, infections are usually ongoing at the time when glomerulonephritis is diagnosed; thus, the term “infection-related glomerulonephritis (IRGN)” has recently been popularly used instead of “post-infectious AGN”. The prognosis of children with PSAGN is generally considered excellent compared with that of adult IRGN cases. However, long-term epidemiological analysis demonstrated that an episode of PSAGN in childhood is a strong risk factor for chronic kidney disease (CKD), even after the complete remission of PSAGN. Although the precise mechanism of the transition from IRGN to CKD remains unknown, its clarification is important as it will lead to the prevention of CKD. In this review, we therefore focus on the possible factors that may contribute to the progression of IRGN into CKD. Four factors, namely, persistent infection, genetic background of the host’s complement system, tubulointerstitial changes, and pre-existing histological damage, are discussed.

Differentiating Staphylococcus infection-associated glomerulonephritis and primary IgA nephropathy: a mass spectrometry-based exploratory study

Staphylococcus infection-associated glomerulonephritis (SAGN) and primary IgA nephropathy (IgAN) are separate disease entities requiring different treatment approaches. However, overlapping histologic features may cause a diagnostic dilemma. An exploratory proteomic study to identify potential distinguishing biomarkers was performed on formalin fixed paraffin embedded kidney biopsy tissue, using mass spectrometry (HPLC–MS/MS) (n = 27) and immunohistochemistry (IHC) (n = 64), on four main diagnostic groups—SAGN, primary IgAN, acute tubular necrosis (ATN) and normal kidney (baseline transplant biopsies). Spectral counts modeled as a negative binomial distribution were used for statistical comparisons and in silico pathway analysis. Analysis of variance techniques were used to compare groups and the ROC curve to evaluate classification algorithms. The glomerular proteomes of SAGN and IgAN showed remarkable similarities, except for significantly higher levels of monocyte/macrophage proteins in SAGN—mainly lysozyme and S100A9. This finding was confirmed by IHC. In contrast, the tubulointerstitial proteomes were markedly different in IgAN and SAGN, with a lower abundance of metabolic pathway proteins and a higher abundance of extracellular matrix proteins in SAGN. The stress protein transglutaminase-2 (TGM2) was also significantly higher in SAGN. IHC of differentially-expressed glomerular and tubulointerstitial proteins can be used to help discriminate between SAGN and IgAN in ambiguous cases.

Antineutrophil cytoplasmic antibody-positive infective endocarditis complicated by acute kidney injury: a case report and literature review

Patients with infective endocarditis (IE) may present with multisystem disturbances resembling autoimmune diseases, such as antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The kidneys are susceptible to damage in IE and AAV, which is a source of diagnostic ambiguity. Therefore, distinguishing infection from an inflammatory process is pivotal for guiding appropriate therapy. We report a 22-year-old man with IE characterized by ANCA positivity and complicated by acute kidney injury. A renal biopsy showed crescentic nephritis with tubulointerstitial lesions. However, transthoracic echocardiography and blood culture provided evidence of IE, and AAV was ruled out. Surgical intervention and antibiotic treatments were successful. We summarized previously reported cases of ANCA-positive IE that had renal biopsy data. We found that ANCA-positive IE can involve multiple organs. The representative renal pathology was crescentic nephritis, focal segmental glomerulonephritis, mesangial cell proliferation, tubular injury, and interstitial oedema. Immunofluorescence showed predominate C3 deposits. Electron microscopy showed electron-dense deposits in the subendothelial or mesangial areas. Eight patients received immunosuppressive therapy with excellent results. Repeated testing for bacterial pathogens and multiple renal biopsies may be useful for diagnosing ANCA-positive IE. With ANCA-positive IE, immunosuppressive therapy along with antibiotic treatments may be beneficial for recovery of renal function.

Vasculitides and glomerulonephritis associated with Staphylocococcus aureus infective endocarditis: cases reports and mini-review of the literature

We reported two cases of Staphylococcus aureus Infective Endocarditis associated with vasculitides and glomerulonephritis respectively, before conducting an online search of previously published similar cases reports. Twenty five references were selected: 15 cases of glomerulonephritis; 2 cases of vasculitis and 8 cases involving both glomerulonephritis and vasculitis. Vasculitides and glomerulonephritis associated with Staphylococcus aureus definite Infective Endocarditis have been reported since 1976. All cases except one described clinical symptoms occurring before or during initial antibiotics treatment. Except kidney, organs that were more frequently affected by vasculitis process were skin, gastrointestinal tract and peripheral nerve and the vessels involved were small to medium size vessels. When antineutrophil cytoplasmic antibodies were evidenced (6 out of the 25 cases (24%)), kidney was the most frequently affected organ. The most commonly observed pattern in Kidney biopsy was membranoproliferative glomerulonephritis with endocapillary proliferation sometimes associated with extra capillary crescents, whether or not antineutrophil cytoplasmic antibodies were evidenced. Right-sided Infective Endocarditis (especially in intravenous drug users) were overrepresented (14 of the 25 cases (56.0%)) in this review. Besides antibiotics, corticosteroids were the most frequently prescribed immunosuppressive treatment both for vasculitides or glomerulonephritis. KEY MESSAGES Vasculitides and glomerulonephritis associated with Staphylococcus aureus definite Infective Endocarditis have been reported since 1976. Except kidney, organs that were more frequently affected (by small to medium size vessel vasculitis) were skin, gastrointestinal tract and peripheral nerve. The most commonly observed pattern in Kidney biopsy was membranoproliferative glomerulonephritis with endocapillary proliferation and right-sided Infective Endocarditis (especially in intravenous drug users) were overrepresented in this review.

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.

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.

IgM ANCA in healthy individuals and in patients with ANCA-associated vasculitis

Low levels of IgM auto-antibodies have been reported in health and disease. IgM anti-neutrophil cytoplasmic antibodies (ANCA) have been reported in patients with ANCA-associated vasculitis (AAV). We sought to investigate if healthy individuals may have IgM ANCA in their sera. The first aim of the study was to determine whether IgM ANCA was present in healthy individuals and in patients with ANCA-associated vasculitis. The second aim was to determine what happens to IgM ANCA levels over time. The third aim was to determine whether bacterial infections affected IgM ANCA levels in non-AAV patients. Sera from healthy individuals and patients with AAV were tested for IgM ANCA by immunofluorescence on fixed neutrophils, immunoprecipitation, Western blot and ELISA. Peripheral blood mononuclear cells were isolated and tested by ELISpot for circulating IgM ANCA B cells. To determine whether infection affected IgM ANCA levels, we studied non-AAV patients with bacterial endocarditis or Staphylococcus aureus bacteraemia and measured IgM ANCA levels over time. IgM ANCA is detectable in both healthy individuals and patients with AAV and the titres decreased with increasing age. Circulating IgM ANCA B cells were identified by ELISpot. In the presence of infection, we could not find a significant change in IgM ANCA levels. We report the presence of low-level specific IgM ANCA in the sera of healthy individuals and in patients with ANCA-associated vasculitis. Bacterial infection did not affect the level of IgM ANCA in this small study.

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.

Immunostaining for galactose-deficient immunoglobulin A is not specific for primary immunoglobulin A nephropathy

Background

Primary immunoglobulin A nephropathy (IgAN) is characterized by IgA1-dominant or codominant glomerular deposits, postulated to be galactose deficient (Gd). However, glomerular IgA deposition can also occur in nonrenal diseases such as liver cirrhosis, psoriasis and inflammatory bowel disease (‘secondary IgAN’) or be an incidental finding in biopsies with other pathologies. A glomerulonephritis resembling IgAN can develop in patients with bacterial, mainly staphylococcal infections [staphylococcal infection-associated glomerulonephritis (SAGN)]. There are no specific histological features to distinguish between these, but differentiation is critical for appropriate management. The aim of this study was to investigate whether a recently described antibody to Gd-IgA1 (KM-55) could aid in differentiating primary IgAN from other conditions with glomerular IgA deposition, especially SAGN.

Methods

We performed a retrospective cohort study of patients who underwent kidney biopsy for clinical indications and were found to have glomerular IgA deposits.

Results

We evaluated 100 biopsies, including primary IgAN (n = 44), secondary IgAN (n = 27), SAGN (n = 13), incidental IgA deposition (n = 8) and lupus nephritis (n = 8). There was no difference in Gd-IgA staining intensity or the proportion of positive cases between primary and secondary IgAN. SAGN and cases with incidental IgA deposits had significantly lower Gd-IgA staining intensity than primary IgAN, but up to 69% of SAGN cases were positive (albeit weaker).

Conclusions

Gd-IgA staining is present not only in primary IgAN, but also in biopsies with secondary IgAN, SAGN and incidental IgA. Weak or negative staining may favor SAGN, especially in the setting of infection, or incidental IgA in the absence of nephritic symptoms or in the presence of other unrelated glomerular pathologies. However, positive staining for Gd-IgA alone is not specific enough for a diagnosis of primary IgAN.

Acute renal failure in a patient with PR3-ANCA and monoclonal immunoglobulin deposition disease: Case report

RATIONALE

Acute renal failure developing over a short period of time with evidence of glomerular disease by urine sediment microscopy characterizes the clinical syndrome of rapidly progressive glomerulonephritis (RPGN), of which the most common causes are ANCA-associated glomerulonephritis (GN), immune-complex mediated GN and anti-GBM disease.

PATIENT CONCERNS

This was a middle-aged gentleman who presented with acute renal failure and a positive PR3-ANCA.

DIAGNOSIS

Renal biopsy showed an unusual combination of PR3-ANCA GN with focal crescents, monoclonal immunoglobulin deposition disease (MIDD) and mesangial IgA deposition on renal biopsy.

INTERVENTIONS

Serum and urine protein electrophoresis (UPEP) and immunofixation showed no detectable monoclonal paraprotein; bone marrow biopsy was negative for plasma cell neoplasia. He received high dose steroids and rituximab.

OUTCOMES

The patient did not respond to treatment and progressed to end-stage renal failure within 2 months after presentation.

LESSONS

To our knowledge, the simultaneous occurrence of MIDD, PR3-ANCA and mesangial IgA has not been reported. This case highlights not only the diagnostic but also the therapeutic challenges that such a complex case presentation poses to clinicians, where the culprit may not always be what would seem most obvious (such as ANCA in a patient with RPGN) but may, in fact, be an underlying and unsuspected disease, or possibly a combination of both.

IgA-dominant glomerulonephritis with a membranoproliferative pattern of injury

Immunoglobulin A (IgA)-dominant membranoproliferative glomerulonephritis (MPGN) is a descriptive term for renal biopsies in which differential diagnoses of unusual IgA nephropathy (IgAN), infection-related GN, or other etiologies are considered. We sought to understand clinical and pathologic features of this finding. Native kidney biopsies with IgA-dominant immune deposits and diffuse MPGN features without significant exudative features or subepithelial deposits were retrospectively reviewed. Two groups (n = 27, 33 biopsies) were identified: patients with chronic liver disease and those without. Patients without chronic liver disease (n = 15) were men (73%, age 40) who presented with nephrotic-range proteinuria, hematuria, renal insufficiency, negative serologic studies, and no history of infection. At a median interval of 3 years, 11 had available follow-up information. Three (27%) progressed to end-stage renal disease. One had recurrent IgA-dominant GN in the renal allograft less than 1 year posttransplant. Four of 5 patients with repeat biopsies had persistent IgA-dominant MPGN. Patients with chronic liver disease (n = 12) had similar biopsy findings, but 42% had concurrent infections, some occult. At a median interval of 7 weeks, 8 patients (80% of those with follow-up) had died and 2 were dialysis dependent. In conclusion, IgA-dominant MPGN was seen in 2 clinical cohorts in this study. In patients without chronic liver disease, this appears to represent either a unique clinicopathologic entity with a poorer prognosis than IgAN or an aggressive variant of IgAN. Patients with chronic liver disease often have underlying infection, and regardless of treatment, die within 1 year because of complex medical conditions.

Acute renal failure by rapidly progressive glomerulonephritis with IgA deposition in a patient concomitantly diagnosed with multibacillary Hansen's disease: a case report

Rapidly progressive glomerulonephritis (RPGN) is a renal disease with an extensive differential diagnosis. This paper reports the case of a 55-year-old female patient diagnosed with Hansen's disease with acute progressive renal impairment after developing lower limb pyoderma. The association between Hansen's and kidney disease has been well documented, with glomerulonephritis (GN) ranked as the most common form of renal involvement. Post-infectious glomerulonephritis (PIGN) in adults has been associated with a number of pathogens occurring in diverse sites. The patient described in this case report had RPGN and biopsy findings suggestive of PIGN with C3 and IgA detected on immunofluorescence and kidney injury secondary to recent infection by Staphylococcus, a well-documented manifestation of renal impairment in patients with Hansen's disease.

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.

Acute glomerulonephritis with large confluent IgA-dominant deposits associated with liver cirrhosis

BACKGROUND

Small glomerular IgA deposits have been reported in patients with liver cirrhosis, mainly as an incidental finding in autopsy studies. We recently encountered nine cirrhotic patients who presented with acute proliferative glomerulonephritis with unusually large, exuberant glomerular immune complex deposits, in the absence of systemic lupus erythematosus (SLE) or monoclonal gammopathy-related kidney disease. Deposits were typically IgA dominant/codominant. Our aim was to further elucidate the etiology, diagnostic pitfalls, and clinical outcomes.

METHODS

We present clinical features and kidney biopsy findings of nine cirrhotic patients with an unusual acute immune complex glomerulonephritis. We also identified native kidney biopsies from all patients with liver cirrhosis at our institution over a 13-year period (January 2004 to December 2016) to evaluate presence of glomerular IgA deposits in them (n = 118).

RESULTS

Six of nine cirrhotic patients with the large immune deposits had a recent/concurrent acute bacterial infection, prompting a diagnosis of infection-associated glomerulonephritis and treatment with antibiotics. In the remaining three patients, no infection was identified and corticosteroids were initiated. Three of nine patients recovered kidney function (one recovered kidney function after liver transplant); three patients developed chronic kidney disease but remained off dialysis; two patients became dialysis-dependent and one patient developed sepsis and expired shortly after biopsy. Within the total cohort of 118 patients with cirrhosis, 67 others also showed IgA deposits, albeit small; and 42 patients had no IgA deposits.

CONCLUSIONS

These cases provide support to the theory that liver dysfunction may compromise clearance of circulating immune complexes, enabling deposition in the kidney. At least in a subset of cirrhotic patients, a superimposed bacterial infection may serve as a "second-hit" and lead to acute glomerulonephritis with exuberant immune complex deposits. Therefore, a trial of antibiotics is recommended and caution is advised before immunosuppressive treatment is offered. Unfortunately, most of these patients have advanced liver failure; therefore both diagnosis and management remain a challenge.

[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.

Acute kidney injury aggravated by treatment initiation with apixaban: Another twist of anticoagulant-related nephropathy

Anticoagulant-related nephropathy (ARN) was initially described in patients on warfarin (as warfarin-related nephropathy) and recently in those using dabigatran. Herein, we report clinical history and kidney biopsy findings in a patient on apixaban (Eliquis). Initiation of treatment with apixaban resulted in aggravation of preexisting mild acute kidney injury (AKI). A few days after apixaban therapy, the patient became oligoanuric, and kidney biopsy showed severe acute tubular necrosis with numerous occlusive red blood cell casts. Only one out of 68 glomeruli with open capillary loops had small segmental cellular crescent. Therefore, there was major discrepancy between the degree of glomerular injury and the glomerular hematuria. Considering that the onset of this AKI was associated with apixaban treatment initiation, we propose that this patient had ARN associated with factor Xa inhibitor (apixaban), which has not previously been described. Monitoring of kidney function is recommended after initiation of anticoagulant therapy.