Development of mycosis fungoides after bone marrow transplantation for chronic myeloid leukaemia: transmission from an allogeneic donor.

We report on a patient who developed donor-derived cutaneous T-cell lymphoma (CTCL) 4 years after successful treatment of chronic myeloid leukaemia with an allogeneic bone marrow transplant. The patient developed an eczematous rash unresponsive to topical therapy and immunosuppression. When CTCL was diagnosed in the recipient, his sibling donor had been attending his local dermatology unit with a maculosquamous rash, which proved subsequently to be mycosis fungoides. An identical pattern of donor and recipient clonality assessment and T-cell receptor gene sequencing indicated that the CTCL was probably transmitted in the bone marrow harvest. This suggests that CTCL cells circulate in the marrow at an early subclinical stage in this disease. This is the second case of donor-derived CTCL reported to date.