Photo Rounds

Painful vesicles on penis

A 32-year-old man presented to his family physician (FP) with a one-week history of multiple painful vesicles on the shaft of his penis associated with tender groin adenopathy. The vesicles broke 2 days earlier and the pain had increased. The patient had similar lesions one year earlier but did not seek medical care at that time. He had 3 different female sexual partners in the past 2 years but had no knowledge of them having any sores or diseases.

What's your diagnosis?


The FP diagnosed this patient with genital herpes. The patient’s herpes culture came back positive and his rapid plasma reagin (RPR) and human immunodeficiency virus (HIV) tests were negative.

Genital herpes presents with multiple transient, painful vesicles that appear on the penis, vulva, buttocks, perineum, vagina, or cervix. The vesicles break down and become ulcers that develop crusts while healing. Recurrences typically occur 2 to 3 times a year. The duration is shorter and less painful than in primary infections. The lesions often heal completely by 8 to 10 days.

The gold standard of diagnosis is viral isolation by tissue culture or polymerase chain reaction (PCR) testing. The culture sensitivity rate is only 70% to 80% and depends upon the stage at which the specimen is collected. The sensitivity is highest in the vesicular stage and declines with ulceration and crusting. The tissue culture assay can be positive within 48 hours but may take longer.

PCR is extremely sensitive (96%) and specific (99%). PCR testing is generally used for cerebrospinal fluid testing in suspected herpes simplex virus encephalitis or meningitis. The Tzanck test and antigen detection tests have lower sensitivity rates than viral culture and should not be relied on for diagnosis.

Antiviral therapy is recommended for an initial genital herpes outbreak. Although systemic antiviral drugs can partially control the signs and symptoms of herpes episodes, they do not eradicate the latent virus. Acyclovir, famciclovir, and valacyclovir are equally effective for episodic treatment of genital herpes, but famciclovir appears somewhat less effective for suppression of viral shedding. Effective episodic treatment of herpes requires initiation of therapy during the prodrome period or within one day of lesion onset. Providing the patient with instructions to initiate treatment immediately when symptoms begin improves efficacy for future outbreaks. Patients with frequent recurrences can choose to take daily antiviral medication for prevention of new outbreaks.

It was too late to initiate antiviral therapy for this patient, so treatment was confined to oral over-the-counter analgesics and topical petrolatum. The FP counseled the patient about the nature of the disease, its transmissibility, and the likelihood of recurrence.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Mayeaux EJ, Carter K. Herpes simplex. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill;2013:735-742.

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