Diffuse lymphadenopathy and fever without a rash: an atypical presentation of secondary syphilis

A woman in her 30s presented to the emergency department with 4 days of fever, headache and back pain. The patient was admitted for pain control, inability to tolerate oral intake and intravenous antibiotics for presumed diagnosis of pyelonephritis. Following admission, CT of the abdomen/pelvis showed multiple prominent pelvic and inguinal lymph nodes, and the patient was noted to have anterior and posterior cervical and submandibular lymphadenopathy on examination. The differential diagnosis was broadened to infectious, haematological, malignant and autoimmune aetiologies of diffuse lymphadenopathy. Workup included serum studies, imaging, lumbar puncture and lymph node biopsy. Rapid plasma reagin (RPR) returned positive with titre 1:16 and confirmatory reactive Treponema pallidum particle agglutination. With an otherwise unrevealing workup, the diagnosis of secondary syphilis was confirmed. This case highlights the differential and diagnostic approach for diffuse lymphadenopathy and an unusual presentation of secondary syphilis. Additionally, it indicates that secondary syphilis can be present even with a relatively low RPR titre.