A 25-year-old woman without a significant medical history was in excellent health until 5 months ago, when she noted mild dyspnea and cough. She was treated with antibiotics but did not improve. Two months before this hospital admission, her dyspnea became severe, the cough persisted, and she had episodes of hemoptysis. She was hospitalized twice and intubated, treated with diuretics, and discharged. Symptoms persisted, and she is now admitted for further evaluation. Her medications include oxygen, furosemide (40 mg bid), diltiazem (180 mg/d), and warfarin (10 mg/d). Medical, social, family, and occupational histories are noncontributory.