Daptomycin-induced eosinophilia without pulmonary involvement

The case of a patient who developed peripheral eosinophilia associated with the use of daptomycin is described.

A 63-year-old man with a history of rheumatic fever during childhood arrived at the emergency department with a chief complaint of left knee pain and swelling. One week before his arrival, the patient received a corticosteroid injection for worsening pain, with minimal relief. The patient's medical history also included type 2 diabetes mellitus, hypertension, coronary artery disease, and hypercholesterolemia. The patient had a documented allergy to cephalexin (skin rash). His initial white blood cell (WBC) count was 16,500 cells/mm(3) (normal, 4,000-10,600 cells/mm(3)), with 89% neutrophils (normal, 40-80%), 5.6% lymphocytes (normal,15-45%), and 0% eosinophils (normal, 0-6%). On hospital day 2, blood cultures and aspiration cultures from the patient's knee were positive for methicillin-sensitive Staphylococcus aureus. Nafcillin and gentamicin were initiated, but on hospital day 7 the patient developed a diffuse, pruritic, macular rash believed to be secondary to nafcillin. At this point, nafcillin treatment was discontinued and daptomycin was initiated. Six days into his treatment, a routine complete blood count revealed a WBC count of 7,620 cells/mm(3), with 11.8% eosinophils. The eosinophils continued to increase, peaking at 34.1% after 26 days of treatment with daptomycin. After cessation of daptomycin, the peripheral eosinophilia resolved. At no point during his hospitalization did the patient have evidence of pulmonary involvement.

A 63-year-old man developed peripheral eosinophilia without evidence of pulmonary involvement while being treated with daptomycin.