Autoantibody against type IV collagen in the basement membranes of renal glomeruli and pulmonary alveoli defines which syndrome?

• A. Hypersensitivity pneumonitis
• B. Wegener Granulomatosis
• C. Pulmonary hypertension
• D. Goodpasture syndrome

Answer: (D)

Autoantibodies against type IV collagen in the basement membranes of the glomeruli and alveoli define a disease in which the immune attack targets the same structural component in both organs. This anti-GBM disease causes binding of IgG along the basement membranes, leading to inflammation and damage in the kidneys and lungs. Clinically, this presents as rapidly progressive glomerulonephritis with hematuria and rising creatinine, often with pulmonary hemorrhage causing hemoptysis. The hallmark laboratory finding is anti-GBM antibodies in serum, and kidney or lung tissue shows a linear IgG pattern along the basement membranes on immunofluorescence.

Other conditions listed involve different mechanisms: granulomatosis with polyangiitis is driven by ANCA-associated vasculitis with granulomatous inflammation rather than anti-GBM antibodies; hypersensitivity pneumonitis stems from an immune response to inhaled antigens; pulmonary hypertension results from vascular remodeling and has no specific anti-GBM antibody target.