The first patient, a 17-year-old female, with no significant past medical history, presented with 1.5 months of facial angioedema, shortness of breath, chest pain, pleural effusion, acne-type rash, and visual loss. There was no history of recent medication prior to onset of symptoms, and a complete blood count was significant for eosinophilia. C1 esterase quantitative was normal. She had received antibiotics and antihistaminic at another facility. Imaging demonstrated diffuse lymphadenopathy and bilateral pleural effusions. Tuberculosis, autoimmune etiology including hereditary angioedema, rheumatologic etiology including sarcoidosis or systemic lupus erythematosus (SLE), and an oncologic process including lymphoma were excluded. 81% eosinophils were identified in the pleural fluid. Bone marrow biopsy was normocellular with trilineage hematopoiesis and approximately 30% eosinophils with some trilobed and multilobated forms. There was no increase in blasts, and some small hypolobated megakaryocytes were present (Figure 1). She was treated subsequently with steroid (prednisone, 60 mg/day and weaned gradually over seven months) alone, and the eosinophil counts dropped rapidly. Her overall eosinophil count remained slightly above the normal range afterwards. She still had some vision and sinus symptoms, but other symptoms resolved. Her absolute eosinophil count declined from 12.9 k/ul (normal 0.1-0.3 k/ul) to 0.4 k/ul over the course of the treatment and continued to remain within the normal range at one-year follow-up.