Review Question - QID 214481

This patient most likely has secondary syphilis as evidenced by his current diffuse maculopapular rash that covers his palms and soles and earlier painless genital chancre (e.g. sore). To confirm the diagnosis, the physician needs to use a treponemal specific test, such as the fluorescent treponemal antibody absorption test.

Syphilis is caused by the spirochete Treponema pallidum and is classified into 3 stages. Primary syphilis presents as a localized disease with a painless chancre on the genitals or oral mucosa. Secondary syphilis defines disseminated disease and classically can present with a maculopapular rash (including the palms and soles), condylomata lata (wart-like, while lesions on genitals), and constitutional symptoms. Tertiary syphilis is a late-stage infection and presents with gummas (chronic granulomas), aortic insufficiency from aortitis, and neurosyphilis. Serologic diagnosis methods are categorized into nontreponemal and treponemal tests. Nontreponemal tests, such as the rapid plasma reagin and venereal disease research laboratory tests, are used for initial screening and assess serum reactivity to cardiolipin-cholesterol-lecithin antigens. In comparison, treponemal tests, such as the fluorescent treponemal antibody absorption test, are confirmatory and detect antibodies against specific treponemal antigens.

Incorrect Answers:
Answer 1: Darkfield microscopy could be used to confirm a diagnosis of syphilis, but the lack of exudative lesions renders this option less optimal. Darkfield microscopy allows direct visualization, but sufficient organisms are usually found in chancre or condylomata lata exudate which are not present in this patient. Since the patient lacks such lesions, serological methods are preferred.

Answer 3: Nucleic acid amplification testing (NAAT) is used for gonorrhea and chlamydia testing. Given this patient’s sexual history, he is likely at high risk of infection for gonorrhea and chlamydia and should be tested. However, his current rash symptoms do not suggest a diagnosis of either disease (e.g. urethritis or epididymitis). Gonococcal infections can present with pustular or vesicular rashes, polyarthralgia, and tenosynovitis. Chlamydia infections can present with conjunctivitis, pharyngitis, and reactive arthritis.

Answers 4-5: Rapid plasma reagin and venereal disease research laboratory tests are serological nontreponemal tests used for screening. Both are non-specific to treponemal antigens and thus usually require a positive treponemal test in conjunction to confirm the diagnosis of syphilis. For patients with a history of syphilis, nontreponemal tests are important for assessing treatment response since titers drop with successful treatment. In comparison, treponemal tests remain positive post-infection.

Bullet Summary:
After a positive screening test, the diagnosis of syphilis requires confirmation by a treponemal specific test, like fluorescent treponemal antibody absorption.