Diagnose This (June 18, 2018)

In the presence of a negative immunofluorescence panel, what is your diagnosis?

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This photomicrograph shows a high power image of a glomerulus with global crescent formation and central tuft fibrinoid necrosis on a PAS stained section. While crescent formation can occur in a variety of kidney diseases, they are typically stratified into three classes: Anti-glomerular basement membrane antibody (AGBM) disease, Pauci-immune type, and immune complex-mediated. These classes are stratified by immunofluorescence with AGBM showing linear IgG staining of the capillary loops and immune complex-mediated showing a pattern of immune complex deposition consistent with the underlying etiology (such as full house staining in lupus nephritis or smudgy IgG staining in fibrillary glomerulopathy). Pauci-immune type shows minimal to no immune complex deposition and is usually associated with ANCA-mediated disease. Of note, endocarditis-associated glomerulonephritis can also present with a pauci-immune and crescentic morphologic pattern and may warrant exclusion in at-risk patients or if clinical concern exists.