AUTHOR=Shi Jiayu , Niu Jingwen , Wu Di , Zhang Lei , Huang Yangyu , Zhang Hui , Guan Hongzhi , Liu Mingsheng , Guan Yuzhou TITLE=Case report: Mononeuropathy multiplex of extranodal natural killer/T-cell lymphoma misdiagnosed as systemic vasculitis JOURNAL=Frontiers in Neurology VOLUME=Volume 14 - 2023 YEAR=2023 URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2023.1283874 DOI=10.3389/fneur.2023.1283874 ISSN=1664-2295 ABSTRACT=Background: Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive non-Hodgkin lymphoma that typically develops in the upper aerodigestive tract. Case presentation: We encountered an ENKTL patient presented with purpura-like rashes and foot drop as initial symptoms, who later developed other peripheral nerves involvement. Nerve conduction study of both motor nerve and sensory nerve showed axonal damage resembling mononeuropathy multiplex. Although the initial response to steroids was encouraging, the patient's symptoms reappeared and aggravated. Biopsy of abdominal subcutaneous fat tissue with additional immunohistochemistry revealed neoplastic NK/T lymphocytes. Conclusions: We reported the first case presented as mononeuropathy multiplex as initial clinical manifestation in ENKTL patients. Lymphoma should be considered in diagnosis of atypical mononeuropathy multiplex patients.