Luetic lymphadenopathy despite negative serology

Laboratory tests can be misleading for the diagnosis of syphilis and false-negative results are possible, but it is rare for both treponemal and non-treponemal tests to prove negative in different stages of the disease. We report on a case of luetic lymphadenopathy, diagnosed by histological examination and supported by immunohistochemical staining for Treponema pallidum, in the absence of skin lesions and positive serology. This case reminds us of how syphilis may present in many different clinical forms and that it should not be excluded only on the basis of negative serological tests. This patient's negative serology was probably due to inadequate initial antibiotic therapy. Given the current widespread use of antibiotics, greater consideration is warranted of the extent to which serological test results are modified by non-specific antibiotic therapies.