Post-transplant lymphoproliferative disorder
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|Post-transplant lymphoproliferative disorder|
|Classification and external resources|
Post-transplant lymphoproliferative disorder (PTLD) is the name given to a B-cell proliferation due to therapeutic immunosupression after organ transplantation. These patients may develop infectious mononucleosis-like lesions or polyclonal polymorphic B-cell hyperplasia. Some of these B-cells may undergo mutations which will render them malignant, giving rise to a lymphoma.
In some patients, the malignant cell clone can become the dominant proliferating cell type, leading to frank lymphoma, a group of B celllymphomas occurring in immunosuppressed patients following organ transplant.
The disease is an uncontrolled proliferation of B cell lymphocytes following infection with Epstein-Barr virus. Production of an interleukin-10, an endogenous anti-T cell cytokine, has also been implicated.
In immunocompetent patients, Epstein-Barr virus causes infectious mononucleosis, characterised by a proliferation of B-lymphocytes which is controlled by Suppressor T cells.
However, calcineurin inhibitors (tacrolimus and cyclosporine), used as immunosuppressants in organ transplantation inhibit T cell function, and can prevent the control of the B cell proliferation.
Depletion of T cells by use of anti-T cell antibodies in the prevention or treatment of transplant rejection further increases the risk of developing post-transplant lymphoproliferative disorder. Such antibodies include ATG, ALG and OKT3.
Polyclonal PTLD may form tumor masses and present with symptoms due to a mass effect, e.g. symptoms of bowel obstruction. Monoclonal forms of PTLD tend to form a disseminated malignant lymphoma.
PTLD may spontaneously regress on reduction or cessation of immunosuppressant medication, and can also be treated with addition of anti-viral therapy. In some cases it will progress to non-Hodgkin's lymphoma and may be fatal.