Eosinophilia After Exposure to Darbepoetin alfa: A Case Report

Introduction: Darbepoetin alfa differs from recombinant human erythropoietin (rEPO) by two additional oligosaccharide chains.These additional oligosaccharide chains are proposed to contribute to darbepoetin's adverse allergic profile.Allergic rashes and erythema can occur in 5% of patients taking darbepoetin.Though allergic reactions are known adverse events associated with this drug, eosinophilia that often accompanies allergic reactions has not been reported as an adverse event of darbepoetin.Herein, we report the first case of recurrent darbepoetin alfa related eosinophilia.Case Presentation: 75-year-old gentleman with several comorbidities underwent trans-carotid artery revascularization (TCAR) procedure.During the prolonged hospitalization, he developed anemia, likely as a result of EPO deficiency in the setting of AKI on CKD.For anemia related to CKD, patient was started on darbepoetin alfa.Soon after, patient started developing asymptomatic eosinophilia.His hemoglobin gradually showed improvement, however, this was accompanied by concomitant eosinophilia, severity of which increased with each subsequent dose.During the period of follow up, patient continued to mount asymptomatic eosinophilia after each darbepoetin dose, without any concomitant hypersensitivity reactions. Conclusions:We report the first case of darbepoetin related eosinophilia and it appears to be a clinically relevant adverse event.Lack of knowledge about this adverse event can result in interruption/ dose reduction of unrelated but necessary medications.Additionally, it may lead to increased healthcare costs due to initiation of extended work up in pursuit to determine underlying etiology of eosinophilia, leading to a superfluous diagnostic odyssey for this rather mild and benign presentation.