How do you approach the workup of pauci-immune glomerulonephritis?

When a kidney biopsy reveals a pauci-immune GN, the Ddx must extend well beyond classic AAV and infective endocarditis. For instance, anti-GBM disease should remain high on the list, as up to 25% of these patients present with a "dual-positive" ANCA, and the characteristic linear IgG staining on IF ...