1. ¹Stem Cell Allogeneic Transplant Unit, Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD, USA
2. ²Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institute of Health, Bethesda, MD, USA
3. ³City of Hope National Medical Center, Duarte, CA, USA
4. ⁴University of Michigan, Ann Arbor, MI, USA
5. ⁵Yale University School of Medicine, New Haven, CT, USA

Correspondence: Dr R Nakamura, City of Hope National Medical Center, 1500E Duarte Road, Duarte, CA 91010, USA. E-mail: rnakamura@coh.org

Received 5 September 2005; Revised 24 October 2005; Accepted 25 October 2005; Published online 9 January 2006.

Abstract

Systemic mastocytosis (SM) is a disease characterized by tissue infiltration of neoplastic mast cells originating from hematopoietic stem cells. Patients with advanced SM have a poor prognosis, and there is no mast cell ablative therapy available for most patients who carry an activating point mutation in the c-kit gene. We report results of a prospective study evaluating the safety, engraftment, and possibility of inducing a graft-versus-mast cell (GvMC) effect after allogeneic nonmyeloablative hematopoietic cell transplantation (HCT) from an HLA-identical sibling. Three patients with advanced SM were transplanted. All achieved complete donor T cell chimerism followed by clinical evidence for GvMC effect. However, all patients experienced disease progression with the longest response duration of 39 months. The GvMC effect can be observed after nonmyeloablative HCT with limited efficacy. Effective cytoreductive therapy prior to HCT may be required for long-term disease control and cure.