Having delivered many dermatology lectures to podiatrists, its surprising how often the issue of sexually transmitted disease (STD) arises - particularly syphilis. Why? You may ask. Well, the plantar surface is a common place for the disease to manifest and so being alert to its presence can help make an earlier diagnosis and referral. The infection is caused by the bacterial spirochaete Treponema Pallidum and it has been a burden to mankind for centuries. The disease is known as the great imitator as it has a very broad range of clinical symptoms making diagnosis tricky, even for the most experienced. Sir William Osler (left) captured this well in the early 19th century when he remarked that “He who knows syphilis knows medicine.”
The rise of syphilis
Syphilis is viewed by many to be a condition of the past, resigned to the dusty old medical textbooks but do not be fooled. Despite a significant decline in the UK in the 1980’s and 1990’s, probably due to behavioural change in the wake of the HIV epidemic, the numbers are creeping back up. In 2015, the total numbers of all STD cases reported was 434 000 in the UK, a year later this had declined (modestly) in 2016 to 420 000, but for syphilis the numbers of cases had continued to rise. There were 5920 cases of the infection reported in the UK in 2016, representing a 12% rise from 2015 when 5281 cases were reported. Since 2012, (when there were 3001 infections) the number of cases has nearly doubled (1) making this the highest number of cases since 1949.
The disease is almost always sexually transmitted (except when acquired congenitally from an infected mother). Following exposure to the infection within about 3 weeks (but up to three months after), a painless papule evolves and rapidly turns into a painless ulcer (or “chancre”) at the point of infection on the skin or mucous membranes (usually the genitalia). It maybe small and present on parts of the body rarely visible. These lesions may remain present for a few months with most resolving spontaneously within 8 weeks (2). Typically, the active ulcer is accompanied by swelling of the regional lymph nodes (lymphadenopathy). For the sufferer, spontaneous resolution is a relief but from here, without a diagnosis and proper treatment, the disease may disseminate via the bloodstream and become more widespread moving into its secondary stage within 6 weeks to 6 months (3).
Secondary symptoms most frequently appear on the skin as rashes - occurring three to twelve weeks after the primary ulcerative lesion. This is where the podiatrist may unwittingly encounter the disease in the clinic. Interestingly, the soles are the most common area where secondary syphilis may manifest as a rash (followed by the trunk, arms, genitals, palms, legs and face ). Typically, this is accompanied with lymphadenopathy. The rashes have a variable presentation across the body and can be macular, papular, nodular, annular, follicular, papulopustular, papulosquamous, psoriasiform, or ulcerative. Typically, on the feet, syphilitic rashes are itch-free, have a coppery coloured hue and are symmetrical. The condition can easily mimic psoriatic lesions on the sole but the coppery hue and accompanying lymphandenopathy may be a clue to an alternative diagnosis. Moreover, lifting of the scale on a syphilitic lesion lacks the pinpoint bleeding sign frequently observed in psoriasis (5).
The genital areas of the patient with secondary syphilis may develop condylomata lata. These are soft, velvety smooth, moist lesions which are difficult to discriminate from genital warts. Although these are limited to the genitals, case reports in the literature have describe similar warty or hyperkeratotic lesions which may mimic verrucae and callus known as “clavi syphilitici” (6) occurring on the foot and in intertriginous areas (figure 1).
Figure 1: Syphilitic Clavi.
(Image from: Moreira C, Pedrosa AF, Lisboa C, Azevedo F. Clavi syphilitici–an unusual presentation of syphilis. J Am Acad Dermatol. 2014;70(6):e131-e2). Click Here for full text
Other more generalised signs and symptoms associated with secondary syphilis include (5):
Weight loss and fever/malaise
Hair loss (patchy “moth eaten” or thinning). Can affect the eyebrows and beard areas.
Lymphadenopathy (generalised with painless lymph nodes)
Neurological symptoms / headaches / meningitis
Joint swelling / arthritis
The second stage of syphilis may last for up to two years and its important to remember that around two-thirds of patients only present for diagnosis when they are in the secondary stage of the disease. At this point the infection is still contagious, although contagion from skin infection is relatively rare. At the end of the secondary stage around three quarters of patients will become asymptomatic with only a quarter entering the tertiary stage where large granuloma can develop (“gummas”) in the skin, sub-cutaneous tissue and within bones leading to serious, life threatening complications (3). Diagnosis and treatment should be undertaken in a specialist centre with follow up as appropriate. Penicillin is the mainstay of oral treatment for the disease.
In the Journal of European Dermatology and Venereology (JEADV) a case report was presented (7) from Brazil of a patient who attended with what appeared to be athletes foot complicating a interdigital fissure which was macerated and hypertrophic along its edges. However, on closer examination, coppery coloured lesions were noted on the soles and palms of the patient. Subsequent testing for syphilis proved positive. What this case highlights, is that on the foot, as with other areas of skin over the body, syphilis may manifest as a psoriaform disease, but also in skin folds (such as the toes) it can also lead to hypertrophy of the skin and macerated lesions. Tinea pedis, callus and warts are considered a differential diagnosis in these cases.
1. Gulland A. Number of cases of syphilis continue to rise. BMJ. 2017;357.
2. Griffiths CE, Barker J, Chalmers R, Bleiker T, Creamer D, editors. Rooks's Textbook of Dermatology. 9th ed. London: Wiley; 2016.
3. Fuchs W, Brockmeyer NH. Sexually transmitted infections. JDDG: Journal der Deutschen Dermatologischen Gesellschaft. 2014;12(6):451-64.
4. Cohen PR, Hymes SR. Secondary syphilis presenting as cutaneous nodules in a patient previously treated for laryngeal carcinoma. Cutis. 1992;49(1):51-4.
5. Baughn RE, Musher DM. Secondary syphilitic lesions. Clin Microbiol Rev. 2005;18(1):205-16.
6. Moreira C, Pedrosa AF, Lisboa C, Azevedo F. Clavi syphilitici–an unusual presentation of syphilis. J Am Acad Dermatol. 2014;70(6):e131-e2.
7. Melo RCC, Antonello V, Ramos MC. Painful interdigital lesion: could it be syphilis? J Eur Acad Dermatol Venereol. 2018;32(4):e129-e30.