Epstein–Barr virus‐positive monoclonal lymphoplasmacytic proliferation associated with neurosyphilis in an immunocompetent patient: A case report

Syphilis is an infectious disease caused by the spirochete bacterium Treponema pallidum. Neurosyphilis results from the infection of the nervous system with Treponema pallidum, which can occur at any stage of syphilis. Neurosyphilis is often overlooked because of its rarity. Early‐stage neurosyphilis with brain mass formation is rare. We present a case of early‐stage neurosyphilis with prominent Epstein–Barr virus (EBV)‐positive monoclonal lymphoplasmacytic proliferation in an immunocompetent patient. A 36‐year‐old man presented with a chief complaint of a progressively worsening headache, a newly developed skin rash, and a fever. Magnetic resonance imaging showed a mass lesion, which measured 18 mm in diameter, in the left frontal lobe of the cerebrum. The patient underwent an emergency operation to remove the abscess. A pathological investigation revealed complex findings. There was an abscess in the cerebrum. Lymphoplasmacytic meningitis was also noted. In addition, a vaguely nodular lesion, which was composed of plasmacytoid and lymphoid cells, was observed around the abscess. Immunohistochemically, an anti‐Treponema pallidum antibody revealed numerous Treponemas around the abscess. In situ hybridization revealed that the plasmacytoid and lymphoid cells were Epstein–Barr encoding region (EBER)‐positive; κ‐positive cells were significantly more prevalent than λ‐positive cells, suggesting light‐chain restriction. Postoperatively, parenteral antibiotics were administered for four weeks. The patient has been free of recurrence for two years since the surgery. No association between neurosyphilis and EBV‐positive lymphoplasmacytic proliferation has ever been reported. Mass formation in early‐stage neurosyphilis is an exceptionally rare event. The present case indicates that in syphilis patients, lymphoproliferative disorders that lead to mass formation may be caused by concomitant EBV reactivation. Furthermore, when treating patients with mass lesions of the central nervous system, it is important to check their medical history and perform laboratory screening for infectious diseases to avoid overlooking syphilis infections.