Abstract

Rapidly progressive glomerulonephritis (RPGN) is a syndrome signified by a precipitous loss of renal function, with features of glomerulonephritis including dysmorphic erythrocyturia and glomerular proteinuria. RPGN is associated with extensive crescent formation, and, thus, the clinical term RPGN is often used interchangeably with the pathologic term crescentic glomerulonephritis (CGN). From an immunopathologic standpoint, primary RPGN is divided into pauci-immune GN (PICG), anti-GBM GN, and immune complex GN. PICG, the most common etiology of primary RPGN, refers to a necrotizing glomerulonephritis with few or no immune deposits by immunofluorescence (IF) or electron microscopy (EM). In most patients, pauci-immune CGN is a component of a systemic small vessel vasculitis such as granulomatosis with polyangiitis (GPA). Approximately 90% of patients with PICG have circulating ANCA antibodies, leading to the nomenclature ANCA-associated vasculitis (AAV). Recent research has identified several other antibodies associated with PICG, which is now understood to be a complex spectrum of disease with considerable overlap in terms of clinical phenotype and outcomes. In addition, several genetic and environmental factors have recently been implicated in the pathogenesis of this disorder. With new prognostic classifications, enhanced understanding of immunopathologic mechanisms, and novel treatment paradigms, clinical and experimental interest in PICG remains high.

Highlights

  • Epidemiology and Clinical OutcomesAt a population level, little is known about the epidemiology and outcome of pauci-immune GN

  • Kain et al demonstrated that a new subtype of Anti-neutrophil cytoplasmic autoantibodies (ANCA), lysosomal membrane protein 2 (LAMP-2) antibodies, are more prevalent than MPO and proteinase 3 (PR3) antibodies in patients with biopsy proven pauci-immune focal necrotizing glomerulonephritis (FNGN) [40]

  • Another line of evidence implicating the role of microbial factors comes from in vivo animal studies evaluating the role of toll-like receptors (TLRs) in the pathogenesis of pauci-immune crescentic GN (PICG) [49, 50]

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Summary

Introduction

Little is known about the epidemiology and outcome of pauci-immune GN. PICG represents up to 80% of cases of RPGN, the incidence of which is estimated to be 7–10 cases per million people per year in the United States [1]. Pauci-immune GN (PICG) has a predilection for whites compared to blacks, with roughly equal representation in men and women [1]. PICG has a 1-year mortality of 80%. The 5-year survival is up to 75% [3]. Dialysis dependency, and pulmonary hemorrhage all worsen the chances of survival. Irreversible, dialysis-dependent renal failure lowers the 5-year survival rate to 35%. We present a case of renal-limited PICG presenting with dialysisdependent renal failure. The ensuing discussion aims to detail the pathophysiology of PICG, while highlighting possible avenues for future scientific inquiry

Nomenclature and Classification
Histopathological Classification
Pathophysiology
Clinical Manifestations and Natural History
Findings
Conclusion
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