Cutaneous Plasmablastic Lymphoma in an Immunocompetent Patient with Long-Term Pyrimethamine Use for Essential Thrombocythemia: A Case Report and Literature Review

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We report a case of Epstein-Barr-virus-(EBV-) positive primary cutaneous plasmablastic lymphoma in a human-immuno-deficiency-virus-(HIV-) negative, immunocompetent 62-year-old female patient. We postulate that her lymphoma development is due to the longstanding use of pyrimethamine for essential thrombocythemia. This has never been described in the literature. 1. Case Report A 62-year-old woman was initially diagnosed with essential thrombocythemia (ET) on the basis of bone marrow aspirate and trephine at age 36 (November 1986), which was later proven to be Janus kinase 2 V617F mutation (JAK2) positive. She was started on hydroxyurea in July 1987 due to platelet counts of>1000 × 109/L and recurrent transient neurological symptoms.This was subsequently changed to pyrimethamine in September 1994 due to concerns about the leukemogenic risk of hydroxyurea. She otherwise maintained good health other than a history of osteoporotic T8 compression fracture