A 74-year-old man arrived breathless with fluid collecting around his right lung. Drainage produced an exudate packed with eosinophils. The fluid kept reaccumulating, and his blood eosinophil count climbed rapidly alongside it.
His doctors worked through the list that any pulmonologist would: malignancy, tuberculosis, bacterial infection, blood in the pleural space. Nothing fit, and he showed no signs of connective tissue disease either.
