Eosinophilic granulomatosis with polyangiitis: histopathological confirmation despite negative serology

A 48-year-old Hispanic female with a history of asthma, chronic eosinophilia of unknown cause with negative antineutrophil cytoplasmic antibodies (ANCAs) and episodic eosinophilic pneumonia presented to the emergency department with two days of flu-like symptoms and painful erythematous macules over the fingers and toes. Labs were notable for an elevated white blood cells of 20.6K/μL (normal 4.0–11.0K/μL) with absolute eosinophil count of 12.36K/μL (normal 0.05–0.55K/μL), aspartate aminotransferase of 58U/L (normal <40U/L), alanine aminotransferase of 72U/L (normal <60U/L), erythrocyte sedimentation rate of 86mm/h (normal 0–31mm/h), and troponin of 0.539ng/mL (normal <0.055ng/mL).