Anti-glomerular Basement Membrane Disease: A Rare Case Report of Changing Clinical Phenotype and Atypicalities

A man in his late 20s, a smoker, presented with nephrotic-range proteinuria and mild renal failure. He had no macroscopic hematuria or decreased urine output. Kidney biopsy was done which revealed a surprising diagnosis of anti-glomerular basement membrane (anti-GBM) disease. He was started on intravenous methylprednisolone, plasma exchanges, and cyclophosphamide. His anti-GBM antibody was, however, weak positive. After five sessions of plasma exchange, he was discharged with a negative anti-GBM antibody. The patient defaulted drugs and presented with rapidly progressive renal failure and hemoptysis after 1½ months. The patient was started on intravenous methylprednisolone, hemodialysis, plasma exchanges, and cyclophosphamide. Repeat biopsy after stabilization was suggestive of anti-GBM disease with fibrocellular crescents. Anti-GBM antibody was negative. Although the patient presented with an estimated glomerular filtration rate of 10 mL/min/1.73 m² and fibrocellular crescents, the patient improved with treatment and was discharged with a serum creatinine of 2.2 mg/dL. This patient had two presentations: one with nephrotic-range proteinuria and mild renal failure, revealing anti-GBM disease on biopsy, and the second with rapidly progressing renal failure which improved with treatment. There were many atypical features in his presentation. Nonabstinence from smoking might be a triggering factor for the second episode. The pathological antibodies may be against a nonconventional epitope or poorly complement fixing, resulting in negative anti-GBM antibody and good recovery in spite of severe renal failure.