Update on endocarditis-associated glomerulonephritis

Trends in acute glomerulonephritis mortality among older adults from 1992 to 2021

This study reports trends in acute glomerulonephritis (AGN) mortality in older adults (aged 65-94 years) and its association with age, period, and birth cohort across 204 countries and territories over the past 30 years, using data from the Global Burden of Disease (GBD) 2021 Study. An age-period-cohort model was used to estimate the overall annual percentage change in AGN mortality (net drift), annual percentage change for individuals aged 65-94 years (local drift), and longitudinal age-specific rates adjusted for period bias and period/cohort relative risks from 1992 to 2021. In 2021, there were 6213 AGN-related deaths globally (95% UI: 4460-7961). Between 1992 and 2021, the net drift for AGN mortality in high socio-demographic index (SDI) countries was 3.15% per year (95% CI 2.62-3.69), compared to - 1.18% per year in low SDI countries (95% CI - 2.01 to - 0.33). High-middle SDI countries had a decline of - 1.49% per year (95% CI - 1.80 to - 1.18), middle SDI countries - 1.52% per year (95% CI - 1.75 to - 1.28), and low-middle SDI countries - 1.78% per year (95% CI - 2.37 to - 1.20). Globally, high SDI countries showed an upward trend in AGN mortality, while others showed a downward trend. Despite the declining mortality in many regions, 15 high SDI countries, 5 high-middle SDI countries, 4 middle SDI countries, 5 low-middle SDI countries, and 3 low SDI countries showed poor or worsening outcomes in the most recent period and birth cohort. These findings suggest that AGN mortality trends are not related to a country's economic development, highlighting the need for high SDI countries to invest more in AGN-related healthcare.

Bartonella Endocarditis-Associated Glomerulonephritis: A Mimicker of Autoimmunity and Vasculitis

Introduction

Bartonella spp. are highly fastidious gram-negative facultative intracellular bacteria which can cause a culture-negative infective endocarditis (IE) with unique clinicopathologic features.

Methods

In this study, we assembled 20 cases of glomerulonephritis (GN) due to Bartonella IE from 3 institutions and compared them with 49 cases of culture-positive IEGN and 30 cases of non-endocarditis infection-related GN (IRGN).

Results

IEGN was seen in approximately 0.15% to 0.4% of native renal biopsies, with Bartonella causing 8% to 21% of IEGN. Patients with Bartonella IEGN had preexisting cardiac valve alterations (75%); antineutrophil cytoplasmic autoantibody (ANCA) positivity (67%); hypocomplementemia (75%); antinuclear antibody positivity (53%); cryoglobulinemia (45%); and hematologic manifestations, including B-symptoms (79%), splenomegaly (59%), thrombocytopenia (83%), and pancytopenia (44%). In 75% of the cases, Bartonella endocarditis was not diagnosed until after kidney biopsy. Pathologically, Bartonella IEGN presented as a focally crescentic GN, which was C3 codominant (80%) with strong IgM (65%) and/or C1q (55%), or pauci-immune (10%), with predominantly mesangial deposits and limited exudative features. At a median follow-up time of 15 months, progression to end-stage kidney disease (ESKD) for all-comers with IEGN was associated with higher creatinine levels at diagnosis, presence of nephrotic syndrome, female sex, and C1q staining intensity. Although delayed diagnosis of infection and immunosuppressive therapy for presumed autoimmune disease before kidney biopsy were more common in Bartonella IEGN than in culture-positive IEGN, neither were associated with ESKD.

Conclusion

IEGNs share laboratory and biopsy features with autoimmunity, which may obfuscate identification of underlying bacterial infection.

Infection associated Vasculitides

Infections can mimic Primary Systemic Vasculitis. Many clinical features and investigations maybe very similar between the two conditions. It is very important for the clinician to be aware of the various infections which mimic vasculitis, since inadvertent immunosuppression in these patients can be fatal. Infections can mimic small, medium or large vessel vasculitis. Infections can produce autoantibodies such as Anti-neutrophil cytoplasmic antibody through molecular mimicry and could confound clinical judgement. In addition to the many infections causing vasculitis, more recently COVID-19 associated vasculitis has been described. The exact pathogenesis of infection associated vasculitis is not clear although direct spread, immune complex deposition and T/B cell activation are proposed. Infection as an etiological agent for primary systemic vasculitis has long been debated but definite evidence for the same is lacking. Many drugs used in daily clinical practice can rarely cause vasculitis. More recently Immune-check point inhibitors-induced vasculitis has been described.

Abiotrophia defectiva endocarditis implicated in antineutrophil cytoplasmic antibody-negative glomerulonephritis

We report a rare case of antineutrophil cytoplasmic antibody (ANCA)-negative pauci-immune necrotising glomerulonephritis (PING) in Abiotrophia defectiva (A. defectiva) endocarditis. A woman in her 50s presented to the hospital with acute kidney injury (AKI), pancytopenia, microscopic haematuria, proteinuria and maculopapular rash. She had A. defectiva sepsis and endocarditis. Serologies were positive for antinuclear antibody and low complement components 3 and 4 but negative for ANCA. A kidney biopsy revealed PING with minimal focal crescents, fibrinoid necrosis and tubulointerstitial fibrosis. She was managed with antibiotics and mitral valve replacement alone. Haemodialysis (HD) was initiated briefly until renal recovery. She remained in complete remission after 2 years. This case illustrates the complex immune response to bacterial endocarditis resulting in ANCA-negative PING. The appropriate use of antibiotics and surgical intervention without immunosuppression in A. defectiva endocarditis led to the resolution of AKI and maculopapular rash.

A Unique Case of Rapidly Progressive Glomerulonephritis in a Patient With Anti-neutrophil Cytoplasmic Antibody (ANCA)-Positive Vasculitis Presenting With Ocular and Cardiac Manifestations

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) can be divided into three distinct clinical entities. Of the three subgroups, granulomatosis with polyangiitis (GPA) is the most common AAV. We present a 33-year-old Hispanic male with no past medical history who presented to the ER with acute-onset pleuritic chest pain and dyspnea. The patient had chronic sinusitis with occasional epistaxis. Initial lab work was significant for hematuria and proteinuria, as well as worsening acute kidney injury (AKI). A renal biopsy confirmed the presence of rapidly progressive glomerulonephritis (RPGN). Autoimmune panels were significant for PR3-ANCA positivity. The patient's clinical picture was most compatible with that of GPA, given the prominence of upper airway symptoms in the setting of new-onset renal failure with erythrocyturia and proteinuria, as well as pulmonary lesions. Cyclophosphamide-based treatment was initiated, in conjunction with glucocorticoids, mesna, and atovaquone. High suspicion for GPA with RPGN should be considered in the younger population who present with new-onset renal failure and pulmonary lesions to present irreversible kidney injury.

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.

ANCA-Negative Pauci-Immune Glomerulonephritis Associated with Bartonella Endocarditis

Kidney complications can occur due to infective endocarditis, one of which is glomerulonephritis. Most often, an immune complex or complement-mediated glomerulonephritis is seen on kidney biopsy. In a minor subset of cases, pauci-immune glomerulonephritis may be present. Most often, such patients will demonstrate the presence of antineutrophil cytoplasmic antibodies (ANCA) on serologic testing. A growing number of cases of ANCA-associated glomerulonephritis due to Bartonella endocarditis have been reported. This type of endocarditis can present diagnostic difficulties given that these patients are often culture negative. Herein, we report a challenging case of ANCA-negative pauci-immune glomerulonephritis showing florid crescents on biopsy that was associated with Bartonella endocarditis.

Atypical post-infectious glomerulonephritis with c-ANCA positivity followed by endocarditis

Post-infectious glomerulonephritis (PIGN), an uncommon variety of glomerulonephritis (GN), is characterized by emergence of nephritic syndrome within a few weeks following an infectious event. PIGN typically presents as a mild condition and tends to resolve by the time of diagnosis for GN. Aggregatibacter actinomycetemcomitans belongs to the HACEK group of bacteria, which constitutes less than 3% of bacteria responsible for community-acquired infective endocarditis. We present a case of 29-year-old man suspected of lymphoma with B-symptoms along with severe splenomegaly and nephromegaly. Shortly after, he developed an episode of nephritic syndrome accompanied by acute kidney injury (AKI) and high titers of cytoplasmic ANCA (c-ANCA)-positivity. Kidney biopsy revealed PIGN with tubulointerstitial nephritis. Despite treatment with antibiotics and corticosteroid, he visited the emergency room due to worsening dyspnea and multi-organ failure. An echocardiogram showed a bicuspid aortic valve with vegetation unseen on previous echocardiogram. He underwent aortic valve replacement immediately without adverse events. Four months after valve replacement, his renal function and cardiac performance have remained stable. We report a case of PIGN with AKI and high titers of c-ANCA appearing later as an infective endocarditis due to Aggregatibacter actinomycetemcomitans. With careful clinical observation and appropriate and timely management, satisfactory outcomes for patient health are possible.

[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.

AKI development is an independent predictor of mortality in infective endocarditis

INTRODUCTION

Infective endocarditis presents a 25% mortality. Acute kidney injury (AKI) develops in up to 70% of the cases. The aim of this study is to evaluate the predictive value of AKI in mortality due to endocarditis and to assess its associated factors.

METHODS

Unicentric and retrospective study including all patients with in-hospital diagnosis of endocarditis between 2015 and 2021. Epidemiological data and comorbidities were collected at baseline. During admission, renal function parameters, infection-related variables and mortality were collected. Using adjusted multivariate models, LRA predictive value was determined.

RESULTS

One hundred and thirty-four patients (63% males, age 72±15 years) were included. Of them 94 (70%) developed AKI (50% AKIN-1, 29% AKIN-2 and 21% AKIN-3). Factors associated to AKI were age (p=0.03), hypertension (p=0.005), previous chronic kidney disease (p=0.001), heart failure (p=0.006), peripheral vascular disease (p=0.022) and glomerular filtration rate (GFR) at baseline (p<0.001). GFR at baseline was the only factor independently associated to AKI (OR 0.94, p=0.001). In-hospital deaths were registered in 46 (34%) patients. Of them, 45 (98%) patients had developed AKI. AKI was independently associated to mortality through diverse multivariate models. GFR loss (OR 1.054, p<0.001) and GFR at baseline (0.963, p=0.012) also predicted mortality during admission.

CONCLUSIONS

AKI development and its severity (GFR loss and AKIN severity) impacts in in-hospital mortality due to infective endocarditis.

Association Between Causative Pathogen and Occurrence of Infection-Related Glomerulonephritis in Infective Endocarditis

Among patients with pathologically proven infective endocarditis, the association of pathogen with occurrence of infection-related glomerulonephritis (IRGN) was examined in 48 case patients with IRGN and 192 propensity score-matched controls. Bartonella was very strongly associated with IRGN (odds ratio, 38.2 [95% confidence interval, 6.7-718.8]; P < .001); other microorganisms were not.

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.

Proteinase‑3‑antineutrophil cytoplasmic antibody‑associated vasculitis secondary to subacute infective endocarditis: A case report

A 58-year-old male patient was admitted to Peking University First Hospital (Beijing, China) due to recurrent hematuria, proteinuria and kidney dysfunction. The patient was positive for proteinase-3 (PR3)-antineutrophil cytoplasmic antibody (ANCA). Pathology of the kidney showed focal proliferative necrotizing glomerulonephritis with crescent formation and immune complex-mediated glomerulonephritis. The patient was diagnosed with PR3-ANCA-associated vasculitis (AAV), received intensive immunosuppressive therapy and experienced two relapses within 1 year. After admission, aortic valve vegetation was observed via echocardiography. The patient subsequently received antibiotic treatment and valve replacement, and achieved complete remission of kidney and cardiac function. The present case emphasized the importance of identifying secondary reasons for ANCA formation, especially infective endocarditis in patients with PR3-AAV.

Glomerulonephritis and Septic Pulmonary Embolism: A Rare but Life-Threatening Complication of Permanent Pacemaker Implantation

Infection-related glomerulonephritis (IRGN) is an immunologically mediated glomerular injury triggered by an extrarenal infection. Infective endocarditis-associated glomerular nephritis is an entity caused by infection of the cardiac valves. IRGN is most common in children, and post-streptococcal glomerulonephritis (PSGN) is commonest in the age group of 2-14 years. In contrast to childhood PSGN and epidemic PSGN, which usually resolve completely with antibiotics, IRGN in adults has a guarded prognosis. Cardiovascular implantable electronic device-associated infective endocarditis (CIED-IE) is a phenomenon for which the incidence is on the rise (0.1-5.1%). The most frequent CIED-IE pathogens were staphylococci or other Gram-positive bacteria. CIED-IE poses difficult management problems for the clinician. We present the case of a 50-year-old patient with a pacemaker who was found to have infective endocarditis and septic embolism.

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.

Bartonella henselae infection-mediated shunt nephritis

Serum anti-neutrophil cytoplasmic antibody (ANCA) positivity with membranoproliferative pattern on renal biopsy can be due to ANCA-associated vasculitis as well as chronic indolent infections. We present the case of an adolescent boy with congenital heart disease and history of cardiac surgery who presented with severe acute kidney injury requiring hemodialysis. Renal biopsy showed membranoproliferative glomerulonephritis with full-house immunofluorescence pattern. Low serum complements, PR3 ANCA positivity and elevated Bartonella immunoglobulin titers suggested a diagnosis of infective endocarditis-associated glomerulonephritis. Cardiac shunt revision and antibiotic therapy lead to improvement in kidney function. Chronic infections lead to formation of immune complexes that may cause deposit within the renal parenchyma and induce production of ANCA. The distinction of ANCA-associated vasculitis and chronic infections causing acute kidney injury is important in determining therapeutic management. While rare in the pediatric population, we highlight the importance in considering indolent infections in patients with acute glomerulonephritis and ANCA positivity, especially with risk factors.

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

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

Rheumatic masqueraders: mimics of primary vasculitis - a case-based review

INTRODUCTION

Vasculitis conditions are often serious and sometimes fatal diseases, therefore it is paramount to diagnose correctly and treat appropriately. Mimics of primary vasculitis can include either non-inflammatory syndromes or secondary vasculitis where the underlying etiology of the vasculitis is being driven by infection, malignancy, drug-effect or other.

AREAS COVERED

This review comprises six individual cases of vasculitis mimics. Each case is presented and the clinical, radiographic, and histological features that distinguish the case from primary vasculitis are highlighted. Key mimics in large, medium and small vessel vasculitis are outlined.

EXPERT OPINION

The diagnosis of vasculitis requires a comprehensive assessment of clinical, radiographic, and histologic features. Clinicians should be familiar with mimics of primary vasculitis conditions. In the case of non-inflammatory mimics, it is important to differentiate from primary vasculitides in order to avoid unnecessary and potentially harmful immunosuppression. For cases of secondary vasculitis, identification of the correct etiologic cause is critical because treatment of the underlying stimulus is necessary for successful management and outcomes.

The Differences in Clinical Manifestations and Prognosis of Infective Endocarditis Patients With Positive Serology to Antineutrophilic Cytoplasmic Antibody Compared to Negative Serology

Previous studies have established a relationship between bacterial proteins and autoimmune diseases through several mechanisms. Infective endocarditis is known for its immunological phenomena, and the presence of antineutrophil cytoplasmic antibodies (ANCA) antibodies has been previously demonstrated in several infectious diseases. This retrospective, comparative, and descriptive study examined the relationship between infective endocarditis and the presence of ANCA antibodies. Ninety infective endocarditis cases were included in the study and tested for ANCA antibodies. The prevalence of ANCA positivity was determined, along with the differences in characteristics and prognosis between infective endocarditis patients with positive and negative serology for ANCA antibodies. The results showed that the characteristics of endocarditis patients who underwent ANCA serology testing were similar to those who did not, except for a higher prevalence of central line and chronic kidney disease in patients with ANCA serology (6.7% compared to 1.1% and 25.6% compared to 12.9%, respectively). Of the 90 endocarditis patients tested for ANCA serology, 18% were ANCA-positive, consistent with other prospective studies. There were no statistically significant differences in the primary outcome, six-month and one-year mortality, between patients with positive and negative ANCA serology. Similarly, in the secondary outcomes of acute kidney injury, heart surgery, and days of hospitalization, there were no statistically significant differences between patients with positive and negative ANCA serology. However, there were statistically significant differences in certain characteristics between the two groups. Patients with positive ANCA serology were found to have a higher prevalence of Enterococcus involvement (29.4% compared to 9.6% with P-value 0.046) and Q fever (23.5% compared to 4.1% P-value 0.02%). In contrast, patients with negative ANCA serology had a higher prevalence of fever (73% compared to 41% P-value 0.033).

A 7-Year-Old Boy with Fever and Dark Urine

A 7-Year-Old Boy with Fever and Dark UrineA 7-year-old boy with surgically repaired tetralogy of Fallot presented for evaluation of fever and dark urine. How do you approach the evaluation, and what is the diagnosis?

Native Tricuspid Valve Infective Endocarditis After Breast Skin Abscess

Tricuspid valve infective endocarditis is a rare disease in non-intravenous drug users. It can occur with congenital heart disease, foreign bodies such as central venous catheters and intracardiac devices, and in immunocompromised patients. In the present case, there was a left-sided breast abscess associated with tricuspid valve endocarditis in a patient without any apparent underlying causative factors. We present a case of a young female in her early 20s who arrived at the emergency department with complaints of fever, epistaxis, and vomiting. On clinical examination, she was found to have a fading 2 cm pinkish left breast skin lesion, which had formed on her breast 10 days ago. Blood cultures identified methicillin-resistant Staphylococcus aureus in the blood. A CT scan of the chest, abdomen, and pelvis revealed splenomegaly and an infective focus in the spleen. Subsequent echocardiography confirmed the diagnosis of infective endocarditis of the native tricuspid valve, which was treated with intravenous vancomycin. There was no history of intravenous drug abuse, congenital heart disease, placement of an intracardiac device, central venous catheter, or an immunocompromised state in this patient. Therefore, the diagnosis of infective endocarditis, characterized by a native tricuspid valve vegetation identified as a consequence of a left breast skin abscess, was made. A high index of suspicion is required for a non-specific presentation of tricuspid valve infective endocarditis and in the absence of any prior history of risk factors for right-sided infective endocarditis. Timely initiation of antibiotics depends on a preliminary clinical diagnosis.

Glomerulonephritis Associated With Infected Cardiac Pacemaker Lead Mimics Infective Endocarditis-Associated Glomerulonephritis With Resolution After Lead Removal: A Case Report and Literature Review

The incidence of cardiac pacemaker lead infections is increasing due to the rise in cardiac implantable device use. These infections mimic infective endocarditis (IE) and cause a variety of complications. However, there is a scarcity of knowledge regarding glomerulonephritis (GN) resulting from cardiac pacemaker-lead infections. This report describes a 71-year-old female who presented with GN associated with a cardiac pacemaker-lead infection. The patient was successfully treated with intravenous (IV) antibiotics, IV steroids, and early surgical removal of the cardiac pacemaker lead, resulting in the resolution of GN. Current guidelines do not address cardiac pacemaker lead infection-associated GN as an indication for lead removal. Given the success of our treatment approach and the rising incidence of cardiac pacemaker infections, we suggest the consideration of early surgical removal of the cardiac lead, in conjunction with antibiotics and steroids, for the treatment of cardiac lead infection associated with GN. Further research is necessary to determine the prevalence and optimal management of this complication.

Perioperative Complications in Infective Endocarditis

Infective endocarditis is a challenging condition to manage, requiring collaboration among various medical professionals. Interdisciplinary teamwork within endocarditis teams is essential. About half of the patients diagnosed with the disease will ultimately have to undergo cardiac surgery. As a result, it is vital for all healthcare providers involved in the perioperative period to have a comprehensive understanding of the unique features of infective endocarditis, including clinical presentation, echocardiographic signs, coagulopathy, bleeding control, and treatment of possible organ dysfunction. This narrative review provides a summary of the current knowledge on the incidence of complications and their management in the perioperative period in patients with infective endocarditis.

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.

Crescentic Glomerulonephritis Due to Enterococcal Endocarditis

Glomerulonephritis following an enterococcal endocarditis is an extremely rare and life-threatening condition. We present the case of a 71-year-old patient with rapidly progressive glomerulonephritis following enterococcal endocarditis after surgical replacement of the aortic valve. The combination of antibiotic therapy, corticosteroid therapy and haemodialysis led to an improvement in renal function; however, the severity of cardiac deterioration resulted in a fatal outcome.

Petechial Rash and Glomerulonephritis: First Presentation of Endocarditis on a Patent Foramen Ovale Closure Device

Patent foramen ovale device closure is rarely associated with complications. This case report is believed to be the first description of a patient with infective endocarditis of a patent foramen ovale closure device presenting as glomerulonephritis. This article serves to educate as to this rare device complication and its unusual presentation. (Level of Difficulty: Intermediate.).

Glomerulonephritis: immunopathogenesis and immunotherapy

'Glomerulonephritis' (GN) is a term used to describe a group of heterogeneous immune-mediated disorders characterized by inflammation of the filtration units of the kidney (the glomeruli). These disorders are currently classified largely on the basis of histopathological lesion patterns, but these patterns do not align well with their diverse pathological mechanisms and hence do not inform optimal therapy. Instead, we propose grouping GN disorders into five categories according to their immunopathogenesis: infection-related GN, autoimmune GN, alloimmune GN, autoinflammatory GN and monoclonal gammopathy-related GN. This categorization can inform the appropriate treatment; for example, infection control for infection-related GN, suppression of adaptive immunity for autoimmune GN and alloimmune GN, inhibition of single cytokines or complement factors for autoinflammatory GN arising from inborn errors in innate immunity, and plasma cell clone-directed or B cell clone-directed therapy for monoclonal gammopathies. Here we present the immunopathogenesis of GN and immunotherapies in use and in development and discuss how an immunopathogenesis-based GN classification can focus research, and improve patient management and teaching.

"Let the Cat Out of the Heart": Clinical Characteristics of Patients Presenting With Blood Culture-Negative Endocarditis Due to Bartonella Species

Patients with blood culture-negative endocarditis due to Bartonella infection frequently presented with fever, cytopenias, kidney failure, and positive PR3-ANCA. Bartonella IgG titers were variable. Patients commonly underwent surgery with overall low mortality.

Systemic Haemophilus parainfluenzae Infection Manifesting With Endocarditis and Membranoproliferative Glomerulonephritis

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

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.

[Global and national trends in the evolution of infective endocarditis]

For the recent 20 years, substantial changes have occurred in all aspects of infectious endocarditis (IE), the evolution of risk factors, modernization of diagnostic methods, therapeutic and preventive approaches. The global trends are characterized by increased IE morbidity among people older than 65 who use intravenous psychoactive drugs. The epidemiological trend is represented by reduced roles of chronic rheumatic heart disease and congenital heart defects, increased proportion of IE associated with medical care, valve replacement, installation of intracardiac devices, and increased contribution of Staphylococcus spp. and Enterococcus spp. to the IE etiology. Additional visualization methods (fluorodeoxyglucose positron emission tomography with 18F-fludesoxyglucose (18F-FDG PET-CT), labeled white blood cell single-photon emission computed tomography (SPECT), and modernization of the etiological diagnostic algorithm for determining the true pathogen (immunochemistry, polymerase chain reaction, sequencing) also become increasingly important. The COVID-19 pandemic has also adversely contributed to the IE epidemiology. New prospects of treatment have emerged, such as bacteriophages, lysins, oral antibacterial therapy, minimally invasive surgical strategies (percutaneous mechanical aspiration), endovascular mechanical embolectomy. The physicians' compliance with clinical guidelines (CG) is low, which contributes to the high rate of adverse outcomes of IE, while simple adherence to the CG together with more frequent use of surgical treatment doubles survival. Systematic adherence to CG, timely prevention and implementation of the Endocarditis Team into practice play the decisive role in a favorable prognosis of dynamically changing IE. This article presents the authors' own data that confirm the evolutionary trends of current IE.

Bartonella henselae Infective Endocarditis: A Rare Cause of Pauci-Immune Necrotizing Glomerulonephritis-A Case Report

Rationale

Bartonella sp. are the most common causes of culture-negative infective endocarditis (IE) cases in the United States. Although, infection-related glomerulonephritis can frequently mimic primary vasculitis due to pauci-immune pattern, majority of previously reported cases of Bartonella henselae-associated glomerulonephritis have immune-complex deposits on immunofluorescence. We present a rare case of B henselae IE-related pauci-immune necrotizing glomerulonephritis. Timely recognition of this atypical presentation led to appropriately directed medical therapy.

Presenting concerns of the patient

A 33-year-old Caucasian male with a history of human immunodeficiency virus (HIV) on highly active antiretroviral therapy (HAART), alcohol abuse, previous subarachnoid hemorrhage (SAH), and recent wisdom tooth extraction (on amoxicillin) was transferred from an outside hospital for further evaluation of severe headache. He was diagnosed with an SAH and right anterior cerebral artery mycotic aneurysm. The serum creatinine at the outside hospital was 292 umol/L (3.3 mg/dL) with a previously normal baseline around 2 years ago. The serum creatinine at our institution was 256 umol/L (3.0 mg/dL). The urinalysis demonstrated +100 protein, +3 blood and 29 red blood cells/high power field. The urine protein creatinine ratio (UPC) was 1.7 g/g. Serologic evaluation was positive for a low C4 10.2 mg/dL, elevated rheumatoid factor 40 IU/mL and an elevated proteinase 3 (PR-3) antineutrophilic cytoplasmic antibodies (ANCA Ab) 4.0 U/mL. A transesophageal echocardiogram (TEE) showed echo densities on both mitral and aortic valve. Blood cultures were negative. Further serologic evaluation was positive for B henselae IgG titer of 1:2560 (normal <1:320) with a negative IgM titer.

Diagnoses

A percutaneous kidney biopsy revealed pauci-immune necrotizing glomerulonephritis, with 14/16 glomeruli globally sclerotic, and 2 glomeruli with active segmental necrotizing lesions. There was no evidence of immune-complex deposition on immunofluorescence or electron microscopy. Clinical findings were consistent with B henselae IE associated mycotic aneurysm and necrotizing glomerulonephritis.

Intervention

Empiric treatment for an active glomerulonephritis with immunosuppressive agents was deferred on admission, given concern for an underlying infectious process and mycotic aneurysms in an HIV-positive patient. He received antibiotic treatment with doxycycline and ceftriaxone with gentamicin for synergy. Despite this, the mitral and aortic valve regurgitation worsened, and he developed congestive heart failure requiring aortic valve replacement and mitral valve repair. The explanted aortic valve was positive for B henselae by polymerase chain reaction (PCR) confirming the diagnosis of B henselae IE.

Outcomes

Immunosuppression was deferred due to timely identification of an atypical presentation of B henselae-associated ANCA antibodies-positive, pauci-immune necrotizing glomerulonephritis. A course of antibiotic treatment resulted in improved renal functions along with undetectable B henselae and PR3 Ab titers. The serum creatinine decreased to 176 umol/L (2 mg/dL) and remained stable 12 months after discharge.

Teaching points

B henselae IE should be suspected in patients with pauci-immune necrotizing glomerulonephritis and culture-negative IE. This is imperative for optimal decision making in the management of such patients. Having high clinical suspicion can avoid unnecessary and potentially deleterious use of immunosuppressive agents.

Case report: Bordetella holmesii: A rare pathogen causing infective endocarditis associated glomerulonephritis

Infective endocarditis (IE) can cause multiorgan dysfunction and chronic kidney disease, in addition to cardiac sequelae. The presentation may be vague and can manifest as acute glomerulonephritis. While the most common pathogens of infective endocarditis are Staphylococcus and Streptococcus species, we report a rare pathogen Bordetella holmesii causing infective endocarditis associated glomerulonephritis. A 20-year-old male patient with tetralogy of Fallot with pulmonary atresia and aortopulmonary collaterals underwent several cardiac surgeries including prosthetic pulmonary valve replacement in the past. He was admitted for 3 days at an outside hospital for fever, cough, and hemoptysis, and diagnosed with streptococcal pharyngitis, for which he received antibiotics. Five weeks later, he presented to our institution with lower extremity edema and gross hematuria. On examination, he was afebrile, normotensive, had a 7-kg weight gain with anasarca, and a systolic murmur, without rash. Investigations revealed elevated serum creatinine, nephrotic range proteinuria, hematuria, and hypocomplementemia, consistent with acute glomerulonephritis. Given his cardiac history, blood cultures were collected from three sites. Broad-spectrum antibiotics were initiated when he subsequently developed fever. Renal pathology on biopsy showed diffuse proliferative immune complex-mediated glomerulonephritis. Transesophageal echocardiogram visualized a vegetation on the pulmonary valve. Bordetella holmesii was ultimately cultured from the prior and current hospitalization. A serum sample detecting microbial cell-free DNA sequencing confirmed Bordetella holmesii at very high levels. After completing 6 weeks of intravenous antibiotics with concurrent angiotensin receptor blockade, his kidney function recovered with improvement in hypocomplementemia and proteinuria. This case report highlights the early recognition and comprehensive evaluation of a rare organism causing IE-associated GN, which allowed for renal recovery and preserved cardiac function.

Autoimmunity in Infection-Related Glomerulonephritis

Introduction

Autoimmune (AI) reactivity in the setting of infection-related GN (IRGN) is often viewed as an epiphenomenon and is not well described.

Methods

We report a cohort of 17 patients with IRGN during a 7-year period that highlights cases with AI reactivity and describes the clinical and pathologic characteristics of IRGN cases associated with AI reactivity.

Results

Of the IRGN cases, 76% had clinical evidence of an autoimmune disease (AD) and/or positive AI serologies. Within the IRGN group with AI reactivity, 12 had positive AI serologies (92%) and 10 had AD (77%). 30% had a prior diagnosis of AD, while the remaining 70% did not have a history of AD and were either diagnosed or suspected of having an AD at the time of biopsy. The most common autoantibody detected was anti-nuclear antibody followed by anti-neutrophil cytoplasmic antibodies and autoantibodies associated with antiphospholipid syndrome.

Conclusion

The study is not sufficiently powered to determine any significance but demonstrates the frequency with which AI features occur in IRGN and should prompt further future investigation. In summary, our findings suggest AI manifestations are common in IRGN.

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.

Endocarditis-associated rapidly progressive glomerulonephritis mimicking vasculitis: a diagnostic and treatment challenge

BACKGROUND

Infective endocarditis (IE)-associated rapidly progressive glomerulonephritis (RPGN) is rarely reported. Sporadic case reports have noted the diagnostic and therapeutic challenge in IE-associated glomerulonephritis because it may masquerade as idiopathic vasculitis.

METHODS

Patients with clinical diagnosis of IE-related RPGN in a tertiary hospital in China between January 2004 and May 2021 were identified and retrospectively reviewed.

RESULTS

Twenty-four patients with IE-associated RPGN were identified. All patients presented with fever and multiorgan system involvement on top of heart and kidneys, spleen (79%, 19/24), skin (63%, 15/24), lung (33%, 8/24) and nervous system (17%, 4/24). Six of the 24 patients (25%) were initially suspected to have ANCA-associated or IgA vasculitis. Forty-five percent of patients are seropositive for ANCA. Renal histology showed mesangial and/or endocapillary hypercellularity with extensive crescents in most patients. C3-dominant deposition was the predominant pattern on immunofluorescence and pauci-immune necrotising crescentic glomerulonephritis was observed in one case. All patients received antibiotics with or without surgery. Six patients received immunosuppressive therapy before antibiotics due to misdiagnosis and seven patients received immunosuppressive therapy after antibiotics due to persistence of renal failure. Three of the 24 patients died due to severe infection. All the surviving patients had partial or complete recovery of renal function.

CONCLUSION

IE-associated RPGN is rare and the differential diagnosis from idiopathic vasculitis can be challenging due to overlaps in clinical manifestations, ANCA positivity and absence of typical presentations of IE. The prognosis is generally good if antibiotics and surgery are not delayed. The decision on introducing immunoruppressive treatment should be made carefully on a case by case basis when kidney function does not improve appropriately after proper anti-infective therapy.Key messagesInfective endocarditis associated RPGN is rare and differentiating it from idiopathic vasculitis can be challenging due to overlap in clinical manifestations, ANCA positivity and occasional absence of typical manifestations of infective endocarditis.Kidney function usually responds to antibiotic therapy alone.Immunosuppressive therapy may be beneficial in carefully selected patients whose kidney function does not improve with antibiotics alone.

The spectrum of renal diseases with lupus-like features: a single-center study

BACKGROUND

A subset of patients without overt systemic lupus erythematosus (SLE) present with biopsy findings typically seen in lupus nephritis (LN). Although a minority eventually develops SLE, many do not. It remains unclear how to classify or treat these patients. Our study attempted to further understand the clinical and pathological characteristics of cases with lupus-like nephritis (LLN).

METHODS

Among 2700 native kidney biopsies interpreted at University of Rochester Medical Center (URMC) from 2010 to 2019, we identified 27 patients with biopsies showing lupus-like features (LL-fx) and 96 with LN. Of those with LL-fx, 17 were idiopathic LLN and 10 were associated with a secondary etiology (e.g., infection/drugs).

RESULTS

At the time of biopsy, the LLN-group tended to be slightly older (44 vs. 35), male (58.8 vs. 17.7%, p = .041), and Caucasian (47.0 vs. 28.1%, p = .005). Chronic kidney disease was the most common biopsy indication in LLN (21.4 vs. 2.8%, p = .001). Both LN and LLN presented with nephrotic-range proteinuria (mean 5.73 vs. 4.40 g/d), and elevated serum creatinine (mean 1.66 vs. 1.47 mg/dL). Tubuloreticular inclusions (TRIs; p < .001) and fibrous crescents (p = .04) were more often seen in LN, while more tubulointerstitial scarring was seen in LLN (p = .011). At mean follow-up of 1684 d (range: 31-4323), none of the LLN patients developed ESRD. A subset of both LN and cases with LL-fx overlapped with other autoimmune diseases.

CONCLUSIONS

Lupus-like pathologic features are seen in a wide array of disease processes. The findings suggest that LLN may be a manifestation of an autoimmune process that overlaps with SLE.

Characteristics and Diagnostic Challenge of Antineutrophil Cytoplasmic Antibody Positive Infective Endocarditis

OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA) has been reported in patients with infective endocarditis. Whether ANCA is associated with certain characteristics of infective endocarditis is unclear. The principal aim of this study is to investigate the clinical implications of ANCA in infective endocarditis and highlight the diagnostic challenge in ANCA-positive patients with infective endocarditis.

METHODS

A retrospective study was conducted in a tertiary hospital in China from August 2012 to December 2021. Patients with a diagnosis of infective endocarditis and available ANCA results were included in the study. The clinical and pathological characteristics were compared between ANCA-positive and ANCA-negative patients.

RESULTS

A total of 237 patients were included. Forty three (18.1%) were ANCA-positive, predominantly c-ANCA/anti-PR3. Compared to ANCA-negative patients, ANCA-positive patients had longer disease duration (P = .004), more frequent purpura (P = .015), macrohematuria (P = .002), proteinuria (P = .043), acute kidney injury (P = .004), and rapidly progressive glomerulonephritis (P = .010). Histologic findings of 8 patients with infective endocarditis-associated glomerulonephritis were reviewed. Two ANCA-positive patients with infective endocarditis presented with pauci-immune necrotizing and crescentic glomerulonephritis. A total of 18.6% of ANCA-positive patients with infective endocarditis were misdiagnosed as ANCA-associated vasculitis.

CONCLUSIONS

ANCA is detected in a substantial proportion of patients with infective endocarditis. The presence of ANCA in infective endocarditis is associated with longer disease duration, more frequent purpura, and kidney involvement. ANCA-positive infective endocarditis may mimic ANCA-associated vasculitis, and the differential diagnosis is challenging. Whether ANCA is pathogenic in infective endocarditis-associated small vessel vasculitis requires further study.

ANCA-associated vasculitis with cardiac valve vegetations in two teenage males: two case reports and a literature review

BACKGROUND

Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis is a term used to describe systemic vasculitides that affect small and medium-sized blood vessels. Granulomatosis with Polyangiitis (GPA), a type of ANCA-associated vasculitis (AAV), is rare in children with an estimated prevalence of 3-4 per million, and even more rare is the manifestation of cardiac abnormalities secondary to ANCA-associated vasculitis in the pediatric population.

CASE PRESENTATION

We discuss the cases of two teenage males who presented with cardiac valvular lesions secondary to GPA in addition to sinus, pulmonary, renal, and cutaneous involvement. These findings of cardiac valvular abnormalities in GPA have rarely been described in the literature in pediatrics. Both patients were treated with rituximab, high-dose methylprednisolone, and therapeutic plasma exchange and showed improvement in their disease manifestations.

CONCLUSIONS

A review of the literature revealed only five pediatric cases of ANCA-associated vasculitis with cardiac manifestations, and interestingly, three of the five had valvular involvement. Subsequent valvular involvement makes obtaining the diagnosis of ANCA-Associated Vasculitis difficult due to concern for underlying infectious endocarditis and can lead to misdiagnosis given the rarity of cardiac involvement in ANCA-associated vasculitis. Routine echocardiogram is not always completed in newly diagnosed AAV, yet cardiac involvement can lead to severe consequences as was seen with our first patient in the form of thromboembolic stroke. We discuss the importance of keeping AAV on the differential when cardiac lesions are present as well as the importance of regular cardiac screening in newly diagnosed patients with AAV, as it is a major factor of cardiac morbidity and mortality in the adult population and can contribute substantially to management decisions.

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.

Endocarditis-Associated C3-Dominant Glomerulonephritis in a Patient With a Solitary Kidney

Infective endocarditis (IE) is still seen globally with acute kidney injuries remaining a common complication of the disease. Histological specimens often display either diffuse or focal endocapillary proliferation as well as neutrophilic infiltration in endocarditis-related renal disease. C3-dominant glomerulonephritis (C3GN) utilizes mechanisms of complement activation unique from IE-associated glomerulonephritis. In C3GN, micrographic review may reveal scattered accumulation of C3 fragments with subepithelial hump formation and mesangial electron-dense deposits that help solidify the diagnosis of this recently discovered pathological phenomenon. Herein, we summarize a clinical case of likely IE-related C3GN without hypocomplementemia in a patient with a single kidney to help compare and contrast the key elements of each process.

A 27-year-old Hispanic man with a past medical history of nephrectomy for renal donation presented to a community hospital with a high fever and altered sensorium. A serum creatinine of 6.98 mg/dL with unknown baselines, nephrotic-range proteinuria, and severe rhabdomyolysis plus methicillin-sensitive Staphylococcus aureus bacteremia were quickly discovered after admission. A later transesophageal echocardiogram showed a hypermobile vegetation along the anterior mitral valve leaflet confirming suspected IE. The patient’s serum C3 and C4 complement levels and antinuclear, myeloperoxidase, and proteinase-3 antibody titers were all within normal limits. A renal biopsy pursued in the etiological investigation of this non-oliguric acute kidney injury revealed a single subepithelial electron-dense deposit and granular immunofluorescent C3 staining in peripheral mesangial segments.

Dominant C3 deposition without associated immunoglobulins can result from in situ localization of bacterial antigens promoting plasmin activation to recruit neutrophils and monocytes to initiate leukocyte-mediated damage. Immunosuppressive therapies for C3GN triggering antibody-independent activation of the alternative or lectin complement pathways may be merited where disease remission becomes difficulty to achieve.

Glomerulonephritis Associated with Infective Endocarditis Showing Serological Positivity for PR3-anti-neutrophil Cytoplasmic Antibody and Anti-glomerular Basement Membrane Antibody

We herein report a case of crescentic glomerulonephritis (GN) associated with infective endocarditis (IE). A 61-year-old-woman presented with a fever and renal dysfunction and was diagnosed with IE. The patient was positive for proteinase 3-anti-neutrophil cytoplasmic antibody (PR3-ANCA) and anti-glomerular basement membrane (GBM) antibodies. Renal biopsy findings showed crescentic GN with isolated deposition of C3c, a serum conversion product of complement C3. Given these clinical findings, the patient was diagnosed with infective endocardis (IE)-associated GN. Antibiotic therapy was continued without immunosuppressive agents. After the initiation of the antibiotics, the fever resolved, and the renal function gradually recovered. This case highlights the notion that laboratory findings should be carefully evaluated with reference to other findings.

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.