Peripheral T-cell lymphoma presenting as fever of unknown origin in a man with deranged liver function tests and pancytopenia.

Peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) is a relatively rare condition in Australia. Here, we report a case of PTCL, NOS in a patient who presented with persistent fever and progressive pancytopenia on a background of mediastinal lymphadenopathy, initially presumed reactive and hepatosplenomegaly with deranged liver function tests. The diagnosis was challenging, with multiple negative blood cultures and inconclusive bone marrow studies, and it required extensive investigations that ultimately revealed the characteristic clinical, histopathological and immunophenotypic features of PTCL, NOS. The patient underwent multiple rounds of multiagent chemotherapy after the diagnosis. This case highlights the difficulty in diagnosing PTCL, NOS and the importance of including it as a differential diagnosis in younger patients who present with constitutional symptoms and hepatosplenomegaly.