Objective Syphilis is an STI that potentially affects any organ. Syphilitic hepatitis and neurosyphilis have been reported in both HIV-uninfected and HIV-infected individuals. The aim of this study was to investigate syphilitic hepatitis and neurosyphilis among HIV-infected individuals during a 13-year period.

Methods This retrospective study included all HIV-infected individuals ≥18 years diagnosed with syphilis between 1 May 2004 and 31 December 2016 in Copenhagen, Denmark. We used the unique 10-digit personal identification number assigned to all individuals in Denmark to link data from two nationwide registers to identify the patients. Patient files were revised to obtain clinical and laboratory data.

Results A total of 509 episodes of syphilis were diagnosed in 427 HIV-infected individuals attending three hospitals in Copenhagen, Denmark. The majority of the patients were men (99.5%), and the majority of men were men who have sex with men (96%). Twenty-seven patients (6%) met the criteria for neurosyphilis, and the neurological symptoms included ocular and auditory abnormalities, headache, paraesthesia, vertigo, facial paresis, motor weakness and unexplained pain in the legs. The patients with neurosyphilis were diagnosed in the secondary stage (84%) and in the early latent (8%) or late latent (8%) stage. Among the patients tested for liver affection, 41% met the criteria for syphilitic hepatitis. The patients with syphilitic hepatitis were diagnosed in the secondary stage (82%), primary stage (10%), and in the early latent (5%) or late latent (3%) stage.

Conclusions The study emphasises that patients with syphilis, also those seen at STI clinics, should undergo a thorough clinical examination and questioning to reveal neurological symptoms. Identification of patients with neurosyphilis is crucial since these patients undergo a different treatment. The study also emphasises that syphilis should be considered as a diagnosis in sexually active patients with liver .