Marked peripheral eosinophilia due to prolonged administration of posaconazole

Introduction. Posaconazole is a triazole antifungal that is used in the treatment of a variety of fungal infections, as well as in the management of mucormycosis (on an off-label basis). Eosinophilia associated with exposure to azole antifungals has been described rarely in the literature. Case presentation. A 31-year-old male on peritoneal dialysis (PD) for end-stage renal disease, secondary to diabetic nephropathy, presented to hospital with abdominal pain after a trip to St Lucia. He was taken to the operating room, where the PD catheter was removed and an abdominal-wall abscess was debrided. Rhizopus species was recovered on culture of the abdominal-wall tissue, and the patient was started on amphotericin B deoxycholate. He was subsequently stepped down to posaconazole, for a planned treatment duration of 12 months. Approximately 43 days after the initiation of posaconazole, it was noted that his peripheral eosinophil count started to rise. No other cause for the eosinophilia was identified. Posaconazole was discontinued, and the patient's eosinophil count began to drop 2 days later. The temporal association of eosinophilia following initiation of posaconazole and the subsequent improvement after drug discontinuation suggests a probable causal relationship. Conclusion. At the time of writing, there have been only two other published cases of azole-associated peripheral eosinophilia. In reporting this case, we hope to increase health-care provider awareness of this rare adverse event. For patients receiving prolonged therapy with posaconazole, periodic monitoring of the complete blood count with differential may be considered.