What condition involves blood clots occluding pulmonary arteries, with more than 95% originating from DVT in the legs?

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

Answer: (B)

Pulmonary embolism is the blockage of pulmonary arteries by a blood clot that has traveled from another part of the body, most commonly deep venous thrombosis in the legs. In fact, more than 95% of pulmonary emboli originate from leg DVTs. When a clot breaks free, it travels through the right side of the heart and lodges in the pulmonary circulation, causing sudden shortness of breath and chest pain from impaired blood flow and gas exchange. The other conditions listed cause lung disease through different mechanisms (inhaled antigens causing hypersensitivity pneumonitis; autoimmune anti-GBM–related pulmonary hemorrhage in Goodpasture; necrotizing granulomatous vasculitis in GPA), not acute vascular occlusion by a thrombus from the legs.