A 34-year-old man comes to the office due to a painless penile ulcer, which he first noticed 3 days ago. He had unprotected sexual intercourse with a new partner a few weeks ago. The patient has no significant medical history and takes no medications. Temperature is 37.1 C (98.8 F). Examination reveals a 2-cm nontender ulcer close to the glans penis with a raised, indurated margin and a clean base. There are no surrounding lesions or vesicles. There are several bilateral enlarged inguinal lymph nodes, which are firm, nontender, and rubbery. Physical examination is otherwise unremarkable. Rapid plasma reagin and HIV testing are negative. Infection with which of the following is the most likely cause of this patient's symptoms?

Question

A 34-year-old man comes to the office due to a painless penile ulcer, which he first noticed 3 days ago.  He had unprotected sexual intercourse with a new partner a few weeks ago.  The patient has no significant medical history and takes no medications.  Temperature is 37.1 C (98.8 F).  Examination reveals a 2-cm nontender ulcer close to the glans penis with a raised, indurated margin and a clean base.  There are no surrounding lesions or vesicles.  There are several bilateral enlarged inguinal lymph nodes, which are firm, nontender, and rubbery.  Physical examination is otherwise unremarkable.  Rapid plasma reagin and HIV testing are negative.  Infection with which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_385e_7b4f_9249_cd22e5dcc9df_MD0001_00 This patient developed a genital ulcer a few weeks after unprotected intercourse, raising suspicion for a sexually transmitted infection. A wide range of pathogens can cause genital ulcers, but a solitary, painless ulcer with heaped-up borders and a clean base usually indicates primary syphilis (syphilitic chancre). Syphilis is caused by Treponema pallidum, a gram-negative spirochete that cannot be cultured and cannot be detected on Gram stain due to its small size. The diagnosis of syphilis relies primarily on nontreponemal (eg, rapid plasma reagin, VDRL) and treponemal (eg, fluorescent treponemal antibody absorption) serologic testing. However, because humoral antibody response often takes 4 weeks to develop, false-negative serologic testing is common early in the course of disease. Nontreponemal tests are particularly susceptible to initial false-negative results (as in this patient); treponemal tests are more sensitive in early infection and are often used preferentially in this setting. Although not widely available, the diagnostic gold standard for syphilis is to directly visualize the organism in tissue scrapings from a cutaneous lesion (eg, chancre). This can involve fluorescent antibody testing or dark-field microscopy, which will show motile, helical spirochetes. (Choice A) L serovars of Chlamydia trachomatis cause lymphogranuloma venereum. Although initial infection is associated with a painless genital ulcer, patients primarily present after the disease has spread to the regional lymph nodes, which results in painful lymphadenitis. This disease is very rare in the United States and occurs mostly in tropical and subtropical regions. (Choice B) Haemophilus ducreyi is a small gram-negative rod that causes chancroid, a sexually transmitted infection characterized by painful (not painless) genital ulcers with an erythematous base. Lesions typically begin as papules or pustules and evolve into an ulcer. More than one lesion is often present. (Choice C) Herpes simplex virus usually causes multiple, bilateral, painful, ulcerating lesions. Initial infections are frequently associated with systemic symptoms (eg, fever, headache, myalgia) and tender lymphadenopathy. (Choice D) Neisseria gonorrhoeae, a gram-negative diplococcus, is a leading cause of cervicitis, urethritis, and pelvic inflammatory disease. Infected patients usually have copious purulent discharge from the urethra; ulcerative genital lesions are not a feature of this organism. Educational objective: Patients with early syphilis (eg, chancre) often have false-negative initial serologic testing. Direct visualization of the organism (Treponema pallidum) by dark-field microscopy or fluorescent antibody testing is the gold standard for diagnosis but is not widely available.

A 34-Year-Old Man Comes to the Office Due to a Painless