Introduction It is known that HIV infected patients with syphilis are more prone to invasion of T. pallidum into central nervous system. Moreover, the diagnosis of neurosyphilis in HIV infected patients can be particularly difficult and challenging since serological tests in the cerebrospinal fluid (CSF) can often be false negative.

Case report A previously healthy 40- year- old male was admitted to neurology department due to acute left side paresthesia, ataxia and diplopia. Since his head CT and CT-angiography scans were without pathological findings and his symptoms started recovering, he was treated conservatively. His symptoms worsened the next day and MR scan revealed right posterior pontine infarction. As part of routine screening for stroke in young patients, he was tested for HIV and syphilis. Serologic tests for syphilis were positive in serum as were screening and confirmatory tests for HIV infection. CD4+ cell count was 282/mm³ and HIV RNA was 9480 copies/ml. CSF analysis showed elevated protein level (0,70 g/L) and lymphocytic pleocytosis (lymphocytes 30/mm³). CSF- RPR and CSF-TPHA were not reactive. However, because of strong clinical suspicion of meningovascular syphilis, additional serological tests for syphilis in CSF, i.e. CSF-IgG-FTA-ABS and CSF-LIA (Line Immuno Assay), were performed: both were positive. After the confirmation of suspected meningovascular syphilis, treatment with intravenous benzylpenicillin was given for 21 days. Neurological symptoms subsided and patient was discharged with minimal neurological sequelae.

Conclusion The correct diagnosis of neurosyphilis in HIV infected patients presents a challenge since serologic tests can be false negative. Therefore, different serologic tests with high specifity and sensitivity should be used, newer tests such as LIA and CIA being particularly helpful. Clinicians should be aware of the characteristics of syphilis and HIV coinfection to establish the correct diagnosis and provide adequate treatment, which will minimise neurological impairments among these patients.