Background An epidemic of syphilis persists in UK men who have sex with men (MSM), often with unusual manifestations. We report a case of syphilis mimicking a lymphoproliferative disorder.

Case A 29-year-old previously well MSM was admitted with 3 weeks of generalised painless lymphadenopathy. He reported malaise, night sweats and joint pain while travelling recently in the Middle East. He was apyrexial and routine bloods were normal apart from mildly raised liver enzymes. Paul Bunnell and HIV antibody tests were negative. His GP screened for STIs but did not include syphilis serology despite the patient describing penile lesions. Clinicians felt that the presentation was highly suggestive of lymphoma. A CT scan showed multiple enlarged lymph nodes in the neck and small bowel mesentery. An open cervical lymph node biopsy was performed. Histopathology showed suppurating granuloma in a reactive lymph node with no evidence of lymphoma. Stains for HIV p24, acid-fast bacilli and fungi were negative. The suggested differential included lymphogranuloma venereum (LGV), cat scratch disease and melioidosis. At GU medicine review he reported sex with multiple partners in the preceding 6 months. He had a blotchy maculopapular rash on his penis and scrotum, though this was treated as “fungal” by junior staff. Molecular tests for chlamydial and gonococcal infections were negative, including throat swabs. Treponema pallidum (TP) antibodies were positive, RPR = 1:256. He was recalled and started on doxycycline for both secondary syphilis and possible LGV. Two weeks later his lymphadenopathy had greatly reduced in size. His original lymph node biopsy was retrieved and TP immunostaining was performed, which revealed a profuse infiltrate of spirochetes.

Conclusion This case highlights the need for clinicians from all specialities to be alert for the many clinical manifestations of syphilis currently prevalent in MSM. Wider use of TP immunostaining in relevant specimens is warranted.