Persistent elevation of peripheral blood myeloid cell counts associated with omalizumab therapy

A case of persistent hematologic abnormalities in a patient receiving long-term omalizumab therapy for severe asthma is reported. During the course of her treatment at an asthma clinic, a 24-year-old woman was noted to have increased white blood cell counts, with elevated myeloid cell counts; the blood abnormalities were first documented more than 12 months previously. The woman had been taking omalizumab for more than 2 years and was also receiving immune globulin therapy for common variable immunodeficiency. Based on the results of bone marrow aspiration and biopsy, she was diagnosed as having mild neutrophilia, possibly related to past corticosteroid therapy, but there was no evidence of a malignancy, a hemophagocytic syndrome, or an infectious, myeloproliferative, or lymphoproliferative process. Pursuant to a multidisciplinary medication review, the use of omalizumab was identified as a potential factor in the myeloid cell elevations and discontinued. About 1 month after omalizumab therapy was halted, the patient's myeloid cell counts normalized. The temporal association of omalizumab use and blood abnormalities in this case, coupled with the lack of data on the drug's long-term hematologic effects, suggests a need for cautious use and close monitoring of omalizumab therapy, particularly in younger patients. A patient with asthma and common variable immunodeficiency developed an elevation of peripheral blood myeloid cells that was first noticed 29 months after the initiation of monthly omalizumab injections. Omalizumab was discontinued, and the abnormality persisted for 1 month after the last dose. The patient's blood count results remained within normal limits 3 months after the last dose.