A previously healthy 39-year-old man presented with a 2-week history of a painless diffuse erythematous rash (Figure 1). He had had multiple sexual partners and unprotected intercourse. Physical examination showed diffuse lymphadenopathy and multiple erythematous macules (diameter, 1-2 cm) with an off-white scaly peripheral collarette (Biett’s sign) (Figure 2), which are typical findings of syphilitic roseola. Screening for sexually transmitted infections revealed positive results on Venereal Disease Research Laboratory (titer 1:256) and Treponema pallidum hemagglutination tests; serologically, he tested negative for human immunodeficiency virus, hepatitis B, and hepatitis C. He received a total of 4.8 million units of penicillin G benzathine over two weeks. At the 1-month follow-up, cutaneous lesions were absent; he was asymptomatic.
Syphilis is a sexually transmitted infection that is re-emerging with increasing prevalence worldwide1,2. Secondary syphilis shows two typical types of rash: one occurring early in this phase called syphilitic roseolas, characterized by light pink to erythematous macules, and one occurring later in this phase named syphilids, marked by erythematous papules2,3. Both have hallmark collarette scales, known as Biett’s sign. Additionally, cutaneous manifestations may demonstrate atypical morphology, such as nodulo-ulcerative, annular, and pustular lesions, among others1,3. Due to varied clinical presentations, secondary syphilis is recognized as “the great imitator” and must be considered as a differential diagnosis of all dermatoses with atypical presentation. All secondary syphilis cutaneous lesions contain highly contagious spirochetes; its non-recognition and late treatment favor an increased risk of disease transmission.