Case #015

A creatinine that was normal six weeks ago and reads 4.2 mg/dL today is what makes this glomerulonephritis rapidly progressive, and set beside haemoptysis it defines a pulmonary–renal syndrome. The differential there is narrow: anti-GBM disease, ANCA-associated vasculitis (granulomatosis with polyangiitis or microscopic polyangiitis), and lupus nephritis. The serology separates them decisively here: a high anti-GBM titre with negative ANCA, negative ANA and normal complement. The absence of ENT involvement, rash, arthralgia and neuropathy argues further against systemic vasculitis, and normal complement with a negative ASO titre excludes post-streptococcal disease. Dysmorphic red cells and red cell casts confirm a glomerular rather than urological source of bleeding. The biopsy is definitive: linear IgG along the basement membrane reflects antibody directed at the α3 chain of type IV collagen, in contrast to the granular deposits of immune-complex disease or the pauci-immune pattern of ANCA vasculitis. Crescents all of the same age indicate a single injurious event rather than the relapsing course typical of vasculitis. Smoking is a recognised trigger for alveolar involvement, since it damages the capillary endothelium and grants the antibody access to pulmonary basement membrane. Treatment is urgent: plasma exchange to strip circulating antibody, cyclophosphamide to halt its production, and corticosteroids to control the inflammation already under way, with exchange continued until antibody is undetectable, typically two to three weeks. Timing decides the kidney here. A creatinine of 4.2 mg/dL with no dialysis requirement yet puts him on the treatable side of the line, since patients presenting above roughly 5.7 mg/dL or already dialysis-dependent seldom recover renal function whatever is given.