Eosinophil infiltrate and degranulation.

(A) Eosinophilic myocarditis (case 1). Low-power photomicrograph showing the presence of a patchy interstitial infiltrate of eosinophils. These infiltrates were focally associated with myocyte damage (hematoxylin-eosin). (B) Eosinophil major basic protein (MBP). Step section of microscopic field shown in (A) stained for eosinophil MBP. Note marked MBP deposition, much of it extracellular, indicating eosinophil degranulation (immunofluorescence). Original magnification for both panels, × 100.