A case of syphilis presenting with prolonged etiology-unrevealed fever, accompanying activated partial thromboplastin time prolongation.

A 58-year-old woman presenting with 3-week-prolonged fever was referred to our department. Her present history and physical examination results were unremarkable. Her activated partial thromboplastin time (APTT) was prolonged. Upon further investigation, anticardiolipin/beta2-glycoprotein I complex antibodies (CL-β2GPI) were detected, occasionally associated with syphilis. On day 14 of her fourth visit as an outpatient, serological tests confirmed the diagnosis, with newly appeared roseola on her palms and soles. She was in the transitional phase to secondary syphilis. Four months later, after successful treatment, her APTT was normalized with CL-β2GPI negative. Syphilis should be considered in patients with APTT prolongation.