Neurosyphilis and the prozone effect

INTRODUCTION: Neurosyphilis (NS) is an entity which still frequently presents to our Neurology Department. The prozone phenomenon occurs in approximately 2% of all cases of late primary syphilis or secondary syphilis; we have found no cases described of prozone and neurosyphilis occurring together. CLINICAL CASE: We present the unusual case of a 44 year old patient with NS and dementia PGP (progressive general paralysis). Initially serum VDRL was negative, but in CSF reacted at dilutions of 1:32. When serum VDRL was repeated using dilutions, it was reactive 1:128 and serum FTA was also reactive. The patient was treated with i.v. crystalline penicillin, after which his condition improved. CONCLUSIONS: We wish to draw attention to the possibility that patients with a dementia syndrome and negative serum VDRL may have the prozone phenomenon, and the laboratory should therefore be asked to do serial dilutions.