Hypereosinophilic syndrome: long-term remission following allogeneic stem cell transplant in spite of transient eosinophilia post-transplant.

A 38-year-old male with progressive myeloproliferative variant of hypereosinophilic syndrome (HES) underwent allogeneic bone marrow transplantation from a matched unrelated donor. The preparative regimen consisted of TBI, cytarabine, and cyclophosphamide. The graft was T-cell-depleted. The patient had slow, but complete, hematologic recovery, and all cells were shown by VNTR analysis to be of donor origin. Five months after transplant, the patient developed prominent eosinophilia (peak 4.1 x 10(9)/L) with dermatographism and very high IL-5 levels. Eosinophils isolated to purity by cell sorting were all of donor origin. Mild increase in immunosuppression led to a normalization of eosinophil count after about 6 months. The patient is now 6 years after transplant, off all medications, and without evidence of disease. Allogeneic stem-cell transplantation is a potentially curative therapy for HES.