A Case Report of Crescentic Glomerulonephritis With Positive Serum Anti-glomerular Basement Membrane Without Linear Glomerular Basement Membrane Immunofluorescent Staining.

Anti-glomerular basement membrane (anti-GBM) disease is an autoimmune disorder characterized by the production of circulating immunoglobulin G (IgG) antibodies that affect the kidneys and lungs, mainly in the form of rapidly progressive crescentic glomerulonephritis and pulmonary hemorrhage. Typically diagnosed on tissue biopsy, findings mainly include glomerular crescent formation, bright linear staining of GBM for IgG on direct immunofluorescence (IF), and the serologic presence of circulating anti-GBM antibodies. Variation in the laboratory results, where histological findings of linear IgG IF staining were present in the absence of circulating anti-GBM antibodies, have recently led to the use of the term "atypical anti-GBM disease," which usually has a distinct benign clinical outcome as compared to typical anti-GBM disease. We report a case of a middle-aged woman who presented with renal failure without lung involvement. Upon further investigation, the patient was found to have strongly positive serum anti-GBM antibodies, but the tissue biopsy did not show typical findings of the anti-GBM disease. The patient showed modest improvement after multiple sessions of plasmapheresis and steroids, with stabilization of her renal parameters after the initial response. In our case, we will address the possibilities of the discrepancies between the serological and histopathological findings.