PTLD
Meaning of PTLD: Epstein-Barr virus sits behind most cases, held in check by an immune system that transplant medication has deliberately turned down.
Definition of PTLD
PTLD stands for post-transplant lymphoproliferative disorder, an uncontrolled growth of lymphocytes that can follow a transplant. It happens because the medications that stop the body rejecting a graft also weaken the surveillance that normally keeps certain virus infected B cells in check. What results ranges from a mild, reversible overgrowth to an aggressive lymphoma.
What is the range of the disorder?
| Category | What the tissue shows |
|---|---|
| Non-destructive lesions | Extra lymphoid cells that preserve the normal architecture of the node |
| Polymorphic | A mixed population of cells that destroys the normal architecture but is not a single clone |
| Monomorphic | A single clone, meeting the criteria for a lymphoma, most often diffuse large B-cell type |
| Classic Hodgkin type | The appearance of Hodgkin lymphoma, the least common form |
The categories are a spectrum rather than separate diseases, which is why PTLD is not simply called a lymphoma. The monomorphic forms are non-Hodgkin lymphoma in every meaningful sense, while the milder forms can settle once immune function is allowed to recover.
Why does a transplant lead to it?
Most people carry Epstein-Barr virus for life after a childhood or adolescent infection. The virus lives quietly inside B lymphocytes, and it is a working immune system, particularly the T cells, that keeps those infected B cells from multiplying. Anti-rejection medication suppresses exactly that surveillance. Freed from it, virus carrying B cells expand, and with each round of division the chance of a further genetic accident grows, which is how a reversible overgrowth becomes a true cancer. A minority of cases carry no detectable virus and tend to appear later, suggesting a different route to the same end.
Who is most at risk, and when?
Risk is highest in the first year after transplant, when immune suppression is heaviest. Someone who has never met Epstein-Barr virus and receives an organ from a donor who carries it faces the greatest risk of all, since a first infection arrives at the moment the immune system is least able to answer it. That combination is most common in children. The intensity of immune suppression matters more than any single drug, and PTLD occurs after transplantation of a solid organ such as a kidney, heart, lung or liver as well as after a stem cell transplant. Blood levels of viral DNA are often tracked as an early warning in those at highest risk.
Also known as
Used in a sentence
The transplant team evaluated the patient for PTLD after persistent lymph node swelling was noted.
Good to know
PTLD reflects a loss of immune control over Epstein-Barr virus rather than an independent cancer, which is why the intensity of anti-rejection medication is central to how the disorder arises and how it is assessed.