Staphylococcal Infection-Related Glomerulonephritis With Cryoglobulinemic Features

Infection-Related Cryoglobulinemic Glomerulonephritis with Serum Anti-Factor B Antibodies Identified and Staining for NAPlr/Plasmin Activity Due to Infective Endocarditis

In this rare case of infection-related cryoglobulinemic glomerulonephritis with infective endocarditis, a 78-year-old male presented with an acute onset of fever and rapidly progressive glomerulonephritis. His blood culture results were positive for Cutibacterium modestum, and transesophageal echocardiography showed vegetation. He was diagnosed with endocarditis. His serum immunoglobulin M, IgM-cryoglobulin, and proteinase-3-anti-neutrophil cytoplasmic antibody levels were elevated, and his serum complement 3 (C3) and C4 levels were decreased. Renal biopsy results showed endocapillary proliferation, mesangial cell proliferation, and no necrotizing lesions on light microscopy, with strong positive staining for IgM, C3, and C1q in the capillary wall. Electron microscopy showed deposits in the mesangial area in the form of fibrous structures without any humps. Histological examination confirmed a diagnosis of cryoglobulinemic glomerulonephritis. Further examination showed the presence of serum anti-factor B antibodies and positive staining for nephritis-associated plasmin receptor and plasmin activity in the glomeruli, suggesting infective endocarditis-induced cryoglobulinemic glomerulonephritis.

An Unusual Case of Seronegative Cryoglobulinemic Glomerulonephritis with Dominant Organized IgA Deposits Associated with Staphylococcal Infection: Casual or Causal Relationship?

Introduction

Cryoglobulinemia refers to the presence of cryoglobulins (CGs) in the serum, encompassing a group of diseases caused by the type of circulating GC. Cryoglobulinemic glomerulonephritis (CryoGN) is the principal manifestation of renal involvement. The diagnosis may be challenging because the hallmark of cryoglobulinemia is the detection of CG in the serum. However, cases of CryoGN without serological evidence of CGs are not uncommon in clinical practice, often diagnosed by anatomopathological findings in the renal biopsy.

Case Presentation

We report the case of an 86-year-old male who developed renal impairment, nephritic syndrome, and nephrotic-range proteinuria, without serological evidence of CGs, associated with staphylococcal bacteremia without apparent focus. Renal biopsy and pathological examination showed a membranoproliferative glomerulonephritis pattern with CD61-negative pseudothrombi. Immunofluorescence microscopy showed atypical IgA-dominant deposits. Electron microscopy revealed amorphous subendothelial and mesangial deposits and organized electrodense deposits within capillary loops (pseudothrombi) with microtubular substructure measuring 20-40 nm in thickness. These findings were consistent with seronegative CryoGN and microtubular organized atypical IgA-dominant deposits.

Discussion

In this report, we discuss the clinical, analytical, and histopathological findings of a rare case of CryoGN without serological evidence of CGs. Regarding the etiology that triggered the glomerular disease in our patient, we conducted an exhaustive study in order to determine the underlying cause of CryoGN. At the time of biopsy, the patient had an active staphylococcal bacteremia. There are reports that postulate that staphylococcal antigens drive activation of immune system and in consequence, could cause this rare form of IgA-dominant glomerulonephritis with cryoglobulinemic features. After ruling out other causes of cryoglobulinemia, we discuss a plausible causal relationship of the staphylococcal infection in the pathogenesis of CryoGN in our patient.

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.

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.

Spectrum of Kidney Diseases in Patients With Hepatitis C Virus Infection

OBJECTIVES

To study the pathologic spectrum of kidney diseases in patients with hepatitis C virus infection (HCV+).

METHODS

Native kidney biopsy specimens in HCV+ patients were reviewed.

RESULTS

A total of 9,836 native kidney biopsy specimens were evaluated from January 2007 to December 2016, of which 273 (2.8%) were from HCV+ patients, and of these, 115 (42.1%) had diagnoses consistent with HCV-associated glomerulonephritis (GN). Non-HCV-associated kidney diseases comprised most diagnoses (158 cases, 57.9%) including non-immune complex-mediated kidney diseases (127 cases, 46.5%) and other immune complex-mediated glomerular diseases (31 cases, 11.4%). Forty-one (40.6%) patients had HCV-associated GN among 101 HCV+ patients from 2007 to 2011 vs 74 (43.0%) patients with HCV-associated GN among 172 HCV+ patients from 2012 to 2016. HCV-associated GN showed five morphologic patterns: focal proliferative (5.2%), diffuse mesangial proliferative (50.4%), diffuse membranoproliferative (28.7%), proliferative GN with crescentic lesions (7.8%), and membranous patterns (7.8%).

CONCLUSIONS

We found a spectrum of pathologic changes in renal biopsy specimens of HCV+ patients, with most having diseases unrelated to HCV infection, HCV-associated GN showing five morphologic patterns, and availability of effective HCV antiviral therapy not yet resulting in major changes in the spectrum of kidney diseases in these patients.

Renal Disease in Cryoglobulinemia

Background

Renal disease in cryoglobulinemia is difficult to grasp and diagnose because it is rare, serological testing is challenging and prone to artifacts, and its morphology is shared by other renal diseases resulting in a spectrum of differential diagnoses. On occasion, a definitive diagnosis cannot even be rendered after immunofluorescence and electron microscopic studies.

Summary

Based on kidney biopsies seen in our routine diagnostic and referral practice, we discuss and illustrate various morphological patterns of renal injury associated with cryoglobulins. We outline key pathophysiologic and clinical aspects associated with cryoglobulinemia induced renal disease and describe morphologic changes with a focus on electron microscopy. We present our practical, morphology-based approach to diagnostic decision-making with special consideration of differential diagnoses and disease mimickers. Since cryoglobulins are rarely tested for prior to kidney biopsy, pathologists and clinicians alike must have a high level of suspicion when interpreting renal biopsies and managing patients.

Key Messages

Cryoglobulinemia-associated glomerulonephritis (GN) is a multifactorial disease which is important to recognize for clinical practice. Morphological features suggestive of cryoglobulinemia-associated GN include a pattern of membranoproliferative GN with abundance of monocytes and the presence of (pseudo)thrombi. By electron microscopy, the main diagnostic features are a prominent infiltration of monocytes/macrophages and the presence of mesangial and subendothelial deposits with frequently curved microtubular/cylindrical and annular substructures.

Infection-Related Glomerulonephritis

Background

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

Summary

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

Key Messages

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

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.

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.

Crystalglobulin-associated nephropathy presenting as MGRS in a case of monoclonal B-cell lymphocytosis: a case report

BACKGROUND

Crystalglobulin-associated nephropathy (CAN), a rare subtype of monoclonal gammopathy, usually associated with multiple myeloma and occasionally monoclonal gammopathy of uncertain significance (MGUS), is characterized by occluding monoclonal pseudothrombi within renal glomerular capillaries and/or interstitial arterioles. Ultrastructurally, these pseudothrombi are unique for having a crystalline substructure. We describe a case of an adult patient with monoclonal B-cell lymphocytosis (MBL) and acute renal failure whose kidney biopsy revealed a rare diagnosis of CAN.

CASE PRESENTATION

A 63-year old male presented with a 2-month history of edema, arthralgia and malaise. He had acute kidney injury with hematoproteinuria on urine analysis. Serum and urine protein electrophoresis were both negative. A renal biopsy however revealed features of CAN. Organomegaly, bone pain and lymphadenopathy were absent. A repeat serum electrophoresis was positive for IgA kappa and a free light chain assay showed elevated free kappa light chains. Flow cytometry done subsequently revealed a diagnosis of MBL, chronic lymphocytic leukemia (CLL) type.

CONCLUSION

CAN in association with MBL/CLL has not been previously described in literature, and our case highlights yet another instance of monoclonal gammopathy of renal significance (MGRS) where a small B-cell clone resulted in extensive renal pathology without systemic manifestations.