Lesson of the month 1: Neurosyphilis mimicking viral encephalitis and ischaemic stroke.

With the incidence of syphilis more than doubling over the last decade, knowledge of its manifestations is of increasing importance. Yet, today's clinicians are less experienced in the recognition of syphilis than the physicians of Osler's day.In this case, a 56-year-old man presented with acute confusion and a history suggestive of encephalitis. Neuroimaging revealed cystic infarcts. He was subsequently tested for HIV and syphilis and found to be positive for both. HIV co-infection had accelerated the rate of neurosyphilis progression. After timely diagnosis and treatment of both conditions, cognitive testing returned to baseline.This case highlights that neuroimaging can often show non-specific infarcts and haemorrhages instead of characteristic syphilitic gummae. This variability adds to the challenge of diagnosis. Thus syphilis serology screening should be sent in those presenting with acute confusion and neuroimaging abnormalities. In cases of cryptogenic stroke, syphilis serology should be added to the screening tests. © Royal College of Physicians 2019. All rights reserved.