Intrathecal IgA synthesis in neurosyphilis

Neurosyphilis can develop during any stage of syphilis. It has recently been reported that cerebrospinal fluid (CSF) data from patients with parenchymal or meningovascular neurosyphilis all show the absence of IgA synthesis and occasionally a concomitant IgM synthesis. In this context, it has been stated that intrathecal IgA synthesis contradicts the diagnosis of neurosyphilis. In our CSF analysis of four patients with definite neurosyphilis we observed an intrathecal synthesis of IgA, IgG and IgM in two patients. Our data are consistent with data of other studies suggesting that about 50% of patients with neurosyphilis show intrathecal synthesis of IgA. Therefore, intrathecal synthesis of IgA does not necessarily contradict the diagnosis of neurosyphilis. We hypothesize that intrathecal synthesis of IgA does not necessarily serve as a discriminating feature between neurosyphilis and other inflammatory central nervous system (CNS) disorders and that other laboratory parameters and the clinical picture have to be taken into account as well.