Proliferative glomerulonephritis with linear immunoglobulin deposition: is this atypical antiglomerular basement membrane disease?

The antiglomerular basement membrane (anti-GBM) antibody disease is marked by the presence of specific antibodies against the non-collagenous domain of the type IV collagen's α3 chain. We describe a case of a 24-year-old Caucasian man, who may have had an atypical presentation of anti-GBM (slow progressive renal insufficiency, massive proteinuria and no detectable circulating anti-GBM antibody). The patient was treated with steroids and cyclophosphamide. This approach failed to attenuate the disease, and so rituximab was initiated with subsequent clinical improvement, normalisation of urinary sediment and marked regression of proteinuria; renal function remained stable. The renal biopsy immunofluorescence was crucial for the diagnosis.