Infectious Disease · Sexually Transmitted Infections
The facts most likely to be tested
Secondary syphilis presents with a diffuse maculopapular rash that characteristically involves the palms and soles.
Patients frequently exhibit generalized lymphadenopathy and systemic symptoms including fever, malaise, and sore throat.
Condylomata lata are highly infectious, flat-topped, wart-like, moist lesions found in intertriginous areas.
The diagnosis is confirmed via nontreponemal screening tests (RPR or VDRL) followed by treponemal-specific confirmatory testing (FTA-ABS or TP-PA).
Jarisch-Herxheimer reaction is an acute febrile response occurring within 24 hours of initiating antibiotic therapy due to the rapid lysis of spirochetes.
The first-line treatment for secondary syphilis is a single dose of intramuscular benzathine penicillin G.
Patchy alopecia (moth-eaten appearance) and mucous patches in the oral cavity are classic, high-yield physical exam findings.
Vignette unlocked
A 26-year-old male presents to the clinic complaining of a non-pruritic rash that started on his trunk and spread to his extremities over the last two weeks. Physical examination reveals a diffuse, copper-colored maculopapular rash involving the palms and soles. He also has generalized lymphadenopathy and several flat, moist, gray-white plaques in the perianal region. He reports a painless genital ulcer that resolved spontaneously six weeks ago.
What is the most appropriate treatment for this patient?
Intramuscular benzathine penicillin G
The patient's presentation of a palmoplantar rash and condylomata lata is diagnostic of secondary syphilis, which is treated with a single dose of intramuscular benzathine penicillin G.
Full handout
High yield triage
Etiology / Epidemiology
Caused by Treponema pallidum; transmitted via direct contact with infectious lesions in unprotected sexual activity.
Clinical Manifestations
Diffuse maculopapular rash involving palms and soles; condyloma lata.
Diagnosis
RPR or VDRL screening followed by FTA-ABS or TP-PA confirmatory testing.
Treatment
Benzathine penicillin G 2.4 million units IM once; penicillin allergy requires desensitization.
Prognosis
High cure rate; monitor for Jarisch-Herxheimer reaction within 24 hours of treatment.
Full handout
Epidemiology & Etiology
Caused by the spirochete Treponema pallidum. Primarily affects sexually active adults with multiple partners or history of STIs. Incidence is rising globally, particularly among MSM populations.
Pertinent Anatomy
Systemic hematogenous dissemination allows the spirochete to colonize the skin, mucous membranes, and lymph nodes. Involvement of the palms and soles is a hallmark of systemic spread.
Pathophysiology
Occurs 4–10 weeks after primary chancre. The spirochete undergoes hematogenous dissemination throughout the body. Immune complex deposition leads to the characteristic mucocutaneous lesions and systemic symptoms.
Clinical Manifestations
Presents with a diffuse, symmetric maculopapular rash that classically involves the palms and soles. Patients exhibit condyloma lata (flat, wart-like, highly infectious lesions) and generalized lymphadenopathy. Systemic symptoms include fever, malaise, and alopecia (moth-eaten alopecia). Red flags include signs of neurosyphilis like cranial nerve palsies or meningitis.
Diagnosis
Screening requires non-treponemal tests (RPR or VDRL), which may be falsely negative in the prozone phenomenon. Confirmatory testing is mandatory using treponemal-specific assays like FTA-ABS or TP-PA. A four-fold rise in non-treponemal titers indicates active infection or reinfection.
Treatment
The first-line treatment is Benzathine penicillin G 2.4 million units IM in a single dose. Penicillin allergy is a major barrier; in non-pregnant patients, doxycycline is an alternative, but desensitization is preferred. Patients must be monitored for the Jarisch-Herxheimer reaction, an acute febrile response to spirochete lysis.
Prognosis
Prognosis is excellent with appropriate antibiotic therapy. Patients must be followed with serial RPR titers at 6 and 12 months to ensure a four-fold decline. Failure to decline suggests treatment failure or reinfection.
Differential Diagnosis
Pityriasis rosea: spares palms and soles
Rocky Mountain Spotted Fever: rash starts on wrists/ankles and moves centrally
Condyloma acuminata: caused by HPV, typically cauliflower-like rather than flat
Drug eruption: lacks systemic lymphadenopathy and classic distribution
Hand-foot-and-mouth disease: associated with oral vesicles and fever