Syphilis has had a longstanding history for dermatologists, who were once called syphilologists. The name syphilis may have derived from a shepherd named Syphilus in the Middle Ages. Syphilis is a sexually transmitted infection with a worldwide distribution. It is caused by a spirochete, Treponema pallidum var pallidum. Non-venereal treponemal infections include yaws, bejel and pinta.
The organism is spread by direct contact and penetrates through abraded skin or mucous membranes. There’s dissemination to lymph nodes and organs within a few hours.
The natural history of untreated syphilis is inoculation, followed by a 14-21-day incubation period before development of the primary syphilitic chancre. There’s hematogenous dissemination over 3-12 weeks resulting in secondary syphilis. Secondary syphilis can last for 3-8 weeks before the organism goes into latency. The latent phase may last for 2-20 years. Sixty-six percent of these patients will not develop further disease but the remaining third can go on to develop tertiary syphilis, which can result in debilitating symptoms.
About 25% of patients will develop neurosyphilis, which can present as meningitis, pseudotumour cerebri, and tabes dorsalis- ataxia, blindness, deafness, Argyll-Robertson pupil and bladder disturbances. Around 25% of patients will develop cardiovascular syphilis, with inflammatory endarteritis of vessels, especially the proximal aorta.
This is the oldest recognized infection. It typically presents before age 2 years. Classic findings include rhinorrhea, pneumonia, neuropathy and perianal fissures. Manifestations of late congenital syphilis include wide-spaced notched central incisors (Hutchinson’s teeth), interstitial keratitis, deafness and bone abnormalities including Sabre shins.
Treponema pallidum cannot be grown in routine culture. Dark-field microscopy can identify motile spirochetes; however, this would not help with an oral lesion as spirochetes are normal flora in the mouth. Specimens can be sent to public health for direct fluorescent antibody testing specific for T. pallidum. Skin biopsy can also be very helpful as the spirochete can be identified with special stains such as Warthin-Starry. Polymerase chain reaction (PCR) can confirm neurosyphilis.
Serologic testing includes non-treponemal tests and treponemal tests. The non-treponemal tests may only become positive 4-5 weeks after infection. In primary syphilis they may only be present in 80% of patients whereas in secondary syphilis they are usually present 100% of the time. Examples of non-treponemal tests VDRL (Venereal Disease Research Laboratory), and RPR (rapid plasma reagin).
Treponemal serologic tests are used to confirm positive non-treponemal test. They detect antibodies to treponemal antigens and remain positive for life unless there was treatment of very early syphilis (25%). Examples include TPHA (T. pallidum hemabsorption test) and MHA-TP (microhemagglutination assay for antibodies to T. pallidum).
Penicillin G is the treatment of choice and there’s no resistance. It’s given intramuscularly and is usually obtained via public health only after the diagnosis of syphilis is confirmed.
primary, secondary and early latent................2.4 million U IM
late latent and tertiary......................................2.4 million U IM q weekly x 3
neurosyphilis...................................................24 million U IV x 14 days
pregnant & HIV patients ................................2.4 million U IM q weekly x 3
pregnant patients who miss a dose must repeat full course
For those who are penicillin allergic options include doxycycline 100 mg po bid x 14 days, tetracycline 500 mg po qid x 14 days, azithromycin 2 gm po x single dose (high failure rate) and Ceftriaxone IV 8-10 days.
Jarisch-Herxheimer reaction refers to endotoxin release, when large numbers of organisms are killed. This usually appears within 24 hours of treatment and peaks within 6 hours of treatment. It’s treated with NSAIDs or aspirin.
Investigate and treat sexual partners, and HIV screening should be offered to all patients with syphilis.
John N. Kraft, MD, FRCPC is a dermatologist in private practice in Markham, ON.
Charles Lynde, MD, FRCP(C) is an assistant professor of dermatology at the University of Toronto.