He did return to the ID clinic six months after his discharge. At that visit, a VDRL serum titer was drawn with a result of 1:64, a decrease from 1:128. His syphilis IgG remained positive, however.
Discussion
Definition and Epidemiology
Syphilis is commonly known as a sexually transmitted disease with primary, secondary, and tertiary (early and late latent) stages.1 Neurosyphilis is defined as a manifestation of the inflammatory response to invasion over decades by the Treponema pallidum spirochete in the CSF as a result of untreated primary and/or secondary syphilis.2 About one in 10 patients with untreated syphilis will experience neurologic involvement.3,4 Before 2005, neurosyphilis was required to be reported as a specific stage of syphilis (ie, a manifestation of tertiary syphilis4), but now should be reported as syphilis with neurologic manifestations.5
A reportable infectious disease, syphilis was widespread until the advent of penicillin. According to CDC statistics,6 the number of reported cases of primary and secondary syphilis has declined steadily since 1943. In the late 1970s and early 1980s, the number of tertiary cases also began to plateau, likely as a result of earlier diagnosis and more widespread use of penicillin. Recent case reports suggest greater prevalence of syphilis among men than women and increased incidence among men who have sex with men.7
Pathogenesis
Syphilis is most commonly spread by sexual contact or contact with an infected primary lesion (chancre). Less likely routes of transmission are placental passage or blood transfusion. Infectivity is greatest in the early disease stages.8
Primary syphilis is marked by transmission of the spirochete, ending with development of secondary syphilis (usually two to 12 weeks after transmission). A chancre commonly develops but is often missed by patients because it is painless and can heal spontaneously.7 The chancre is also often confused with two other sources of genital lesions, herpes simplex (genital herpes) and Haemophilus ducreyi (chancroid). In two-thirds of cases of untreated primary syphilis, the infection clears spontaneously, but in the remaining one-third, the disease progresses.8
Secondary syphilis, with or without presence of a chancre, manifests with constitutional symptoms, including lymphadenopathy, fever, headache, and malaise. Patients in this disease phase may also present with a generalized, nonpruritic, macular to maculopapular or pustular rash. The rash can affect the skin of the trunk, the proximal extremities, and the palms and soles. Ocular involvement may occur, especially in patients who are coinfected with HIV.8 In either primary or secondary syphilis, infection can invade the central nervous system.1
During latent syphilis, patients show serologic conversion without overt symptoms. Early latent syphilis is defined as infection within the previous year, as demonstrated by conversion from negative to positive testing, or an increase in titers within the previous year. Any case occurring after one year is defined as late or unknown latent syphilis.8
Tertiary syphilis is marked by complications resulting from untreated syphilis; affected patients commonly experience central nervous system and cardiovascular involvement. Gummatous disease is seen in 15% of patients.1
The early stages of neurosyphilis may be asymptomatic, acute meningeal, and meningovascular.1,4,8,9 Only 5% of patients with early neurosyphilis are symptomatic, with the added potential for cranial neuritis or ocular involvement.1 The late stages of neurosyphilis are detailed in the table.1,4,8
Diagnosis
A diagnosis of syphilis is made by testing blood samples or scrapings from a lesion. In patients with suspected syphilis, rapid plasma reagin (RPR) testing or a VDRL titer is commonly ordered. When results are positive, a serum treponemal test is recommended to confirm a diagnosis of syphilis. Options include the fluorescent treponemal antibody absorption test (FTA-ABS) and the microhemagglutinin assay for antibody to T pallidum (MHA-TP).5
If neurologic symptoms are present, a CSF sample should be obtained, followed by the same testing. A confirmed diagnosis of neurosyphilis is defined by the CDC as syphilis at any stage that meets laboratory criteria for neurosyphilis5; these include increased CSF protein or an elevated CSF leukocyte count with no other known cause, and clinical signs or symptoms without other known causes.7
Treatment
Treatment of syphilis generally consists of penicillin, administered intramuscularly (IM) or IV, depending on the stage. According to 2006 guidelines from the CDC,10,11 treatment for adults with primary and secondary syphilis is a single dose of IM penicillin G, 2.4 million units. If neurosyphilis is suspected, recommended treatment is IV penicillin G, 18 to 24 million units per day divided into six doses (ie, 3 to 4 million units every four hours) or continuous pump infusion for 10 to 14 days.10-12 Follow-up is recommended by monitoring CSF titers to ensure clearance of infection; retreatment may be required if CSF abnormalities persist after two years.11