An Atypical Syphilis Presentation
We present a case of lichenoid secondary syphilis in the genital area in the absence of other cutaneous or systemic manifestations. The patient did not experience an eruption on the palmar or plantar surfaces, which is rare. This case also is unique because of the intense pruritus associated with the genital lesions, a remarkable dissimilarity from typical secondary syphilitic eruptions that tend to be asymptomatic.
Practice Points
- Syphilis retains its reputation as “the great imitator” due to its wide variability in clinical presentation and propensity for misdiagnosis.
- Lichenoid syphilis is a well-described cutaneous presentation of secondary syphilis, though the characteristics of these lesions remain highly variable and require a high degree of clinical suspicion.
- Treponema pallidum is partially susceptible to most β-lactam antibiotics in primary and early secondary stages of infection; thus, use of these medications can obscure symptoms without adequately treating the infection.
Differential Diagnosis
It has been estimated that approximately 8% of cutaneous syphilitic lesions demonstrate morphology and distributions suggestive of other dermatologic conditions, including atopic dermatitis, pityriasis rosea, psoriasis, drug-induced eruptions, erythema multiforme, mycosis fungoides, and far more uncommonly lichenoid lesions,16,17 as in our case.
Histopathology
It has been demonstrated that the gross appearance of the secondary syphilitic lesion depends both on the degree of inflammatory infiltrate and the extent of vascular involvement producing ischemia of the skin.1 Our case presented with small, flat-topped, papular lesions that grossly resembled lichen planus and were ultimately shown to be the product of dense lymphomononuclear infiltration extending perivascularly and throughout the superficial and deep dermis.
Biopsy of a lesion is one means of diagnosis, though the histologic appearance of secondary syphilis can mimic many other diseases. In primary and secondary syphilis, skin biopsy characteristically shows central thinning or ulceration of the epidermal layer with heavy dermal lymphocyte infiltration, lymphovascular proliferation with endarteritis, small-vessel thrombosis, and dermal necrosis. Lichen planus–type dermatitis is histologically characterized by hyperkeratosis, irregular epidermal hyperplasia, and a dermoepidermal junction that may be obscured by a dense lymphomononuclear infiltrate.9 The specimen taken from our patient showed minimal infiltrate in the papillary dermis, suggesting a diagnosis of secondary syphilis with lichenoid features. Despite a gross appearance consistent with lichen planus, the biopsy lacked the hydropic degeneration of the basal layer and keratinocyte necrosis that typically characterize this condition.
,Diagnosis
Serologic testing for syphilis infection is comprised of nontreponemal and treponemal studies. Nontreponemal testing, which includes the RPR and VDRL test, detects antibodies to cardiolipin-lecithin antigen, a lipid component of the cell membranes of T pallidum. Because the specificity of these tests is fairly low, they typically are used only for screening and monitoring of disease progression and/or response to treatment. Approximately 25% of cases in the United States of primary syphilis are not detected by nontreponemal testing, whereas a nonreactive test nearly always excludes a diagnosis of secondary or latent-stage syphilitic infection.9 Indeed, nontreponemal studies show the highest antibody titers during the late secondary and early latent stages of infection with declining titers thereafter, even in the absence of antibiotic treatment. In our case, diagnosis was made by biopsy and RPR was used for staging; RPR was reactive at a dilution of 1:32, indicative of secondary or early latent infection.
Treponemal testing, which includes the fluorescent treponemal antibody absorption test, and multiplex flow immunoassay detects antibodies that are specific to syphilis infection. Treponemal antibodies are detectable earlier in the course of infection than nontreponemal antibodies and remain permanently detectable even following treatment. Because of its high specificity, treponemal testing often is used to confirm diagnosis after positive screening with nontreponemal tests.4 Positive fluorescent treponemal antibody absorption testing and positive multiplex flow immunoassay may be used to confirm the diagnosis of T pallidum infection.
The tertiary stage of syphilis infection can occur years after conclusion of the secondary stage and is comprised of one or more of the following: gummas, aortic dilatation or dissection, and neurosyphilitic manifestations such as tabes dorsalis or general paresis.1 It is of vital importance to identify syphilis infection prior to the onset of the tertiary stage to prevent substantial morbidity and mortality.
Treatment
Our patient’s symptoms abated after empiric treatment with amoxicillin for presumed streptococcal throat infection after he presented to the emergency department with odynophagia, which is not surprising given the moderate-spectrum coverage of this β-lactam antibiotic as well as the near-complete susceptibility of Treponema spirochetes to amoxicillin in primary and secondary syphilis with notably lower efficacy in latent or tertiary disease. It was essential to treat the patient with a single dose of intramuscular benzathine penicillin G 2.4 million U, which has been shown to reliably prevent recurrence of infection or progression to tertiary syphilis.18
Conclusion
We present a rare case of lichenoid secondary syphilis in the absence of lesions on the palmar and plantar surfaces. The patient lacked any other cutaneous or systemic manifestations, except for odynophagia in association with oral mucosal lesions. He denied any new sexual partners and did not recall having a primary chancre. Also strikingly unusual in this case was the intense pruritus associated with the genital eruption, which is unlike the classic lack of symptoms experienced in the great majority of eruptions due to secondary syphilis. A clinical appreciation of the many cutaneous manifestations of syphilis infection remains critical to early identification of the disease prior to progression to the tertiary stage and its devastating sequelae.
