A transplant patient who had serologic evidence of previous Epstein-Barr virus infection was taking high levels of immunosuppressive medications. He presents with generalized lymphadenopathy, fever, night sweats, weight loss, abdominal pain, and tonsillitis. The dosage of immunosuppressive drugs given to the patient is decreased, and the lymphadenopathy regresses. Which of the following is the best diagnosis for this patient?

All of the choices are associated with EBV. The patient most likely has lymphoproliferative disorder (posttransplant) (d), a polyclonal response to reactivation or acquisition of EBV in persons on immunosuppressive therapy to prevent transplant rejection. The disorder responded to reduction of the immunosuppressive agent, a response not expected if the patient had Burkitt lymphoma (a) or Hodgkin lymphoma (b), more aggressive monoclonal B-cell lymphomas that often require anti-lymphoma treatment. Infectious mononucleosis (c) occurs in immunocompetent individuals. NPC (e) does not fit the vignette.