Cutaneous Post-transplant Lymphoproliferative Disorder.

Post-transplant lymphoproliferative disorders (PTLD) involve T- or B-cell proliferation in an immunosuppressed transplant recipient. It usually presents at extra-nodal sites and can affect several organs. Cutaneous manifestations of PTLD are relatively rare and can be very heterogeneous. We report a case of a 36-year-old male cardiac transplant recipient on long-term immunosuppression (ciclosporin, azathioprine, and prednisolone) who presented with a three-month history of a painless ulcer on the right lower leg. A skin biopsy showed a dermal atypical lymphoid infiltrate positive for PAX5, CD20 and MUM1 on immunohistochemistry and EBV with in-situ hybridisation and a 70% Ki-67 cell proliferation index. A whole body fluorodeoxyglucose (FDG) positron emission tomography (PET) scan showed increased tracer uptake corresponding to the site of the cutaneous ulcer, the anterior cortex of the right lower tibia, an area adjacent to the right superficial femoral artery and the right inguinal node. These findings were in keeping with monomorphic B-cell post-transplant lymphoproliferative disorder (PTLD) consistent with diffuse large B-cell lymphoma, non-germinal centre subtype. Cessation of azathioprine and treatment with an anti-CD20 antibody, rituximab, led to clinical resolution of the ulcer and a negative FDG-PET scan, with no disease recurrence to date. We present a rare case of monomorphic PTLD with cutaneous involvement, presenting with a solitary, painless ulcer, which was successfully treated with a reduction in immunosuppression and additional rituximab monotherapy, given the aggressive subtype. PTLD can arise many years post-transplant and is a serious, potentially life-threatening complication. Therefore, early recognition and prompt treatment are of paramount importance.