Dermatology MCQ - Viral Infections - Primary herpes genitalis

A 20-year-old woman presents with a 3-day history of painful genital ulcers, dysuria, and tender bilateral inguinal lymphadenopathy. On examination, you observe multiple, shallow, erythematous-based ulcers with scalloped borders on the labia majora and perineum. She is febrile (38.5°C) and reports a headache and myalgia. A Tzanck smear prepared from the base of an ulcer shows multinucleated giant cells. Which of the following is the most likely causative agent and its typical latency site after primary infection?

A) Treponema pallidum; persists in extracellular spaces
B) Haemophilus ducreyi; remains localized to ulcer site
C) Herpes simplex virus type 2 (HSV-2); establishes latency in sacral dorsal root ganglia
D) Chlamydia trachomatis; persists as elementary bodies in mucosal cells
E) Klebsiella granulomatis; resides within histiocytes

Correct Answer: C) Herpes simplex virus type 2 (HSV-2); establishes latency in sacral dorsal root ganglia

Explanation

This presentation is classic for primary herpes genitalis, the initial symptomatic outbreak of genital herpes.

Key Clinical Features:

• Symptoms: Painful genital ulcers, dysuria (often severe), tender lymphadenopathy, and systemic symptoms (fever, headache, myalgia) indicate a primary infection.

• Examination: Multiple, shallow, erythematous-based ulcers with scalloped borders are highly characteristic. These begin as vesicles that rapidly rupture.

• Tzanck Smear: The finding of multinucleated giant cells with molded nuclei and marginated chromatin is a classic, though not specific, test for herpesvirus infections (HSV or VZV).

Virologic Pathogenesis:

• Causative Agent: Herpes simplex virus type 2 (HSV-2) is responsible for the majority of genital herpes cases, though HSV-1 is an increasingly common cause via orogenital contact.

• Latency: After primary infection, HSV establishes lifelong latency in the sensory nerve ganglia. For genital infections, the virus resides in the sacral dorsal root ganglia (S2-S5).

• Reactivation: From the ganglia, the virus can reactivate, travel back along the nerve, and cause recurrent outbreaks at or near the original site of infection. These recurrences are often milder and lack systemic symptoms.

Why Not the Other Options?

• (A) Treponema pallidum: Causes syphilis, which typically presents with a single, painless chancre (ulcer with a indurated base) and non-tender lymphadenopathy. It does not produce multinucleated giant cells.

• (B) Haemophilus ducreyi: Causes chancroid, which presents with painful, purulent ulcers with ragged edges and tender lymphadenopathy that may suppurate. It is not associated with multinucleated giant cells.

• (D) Chlamydia trachomatis: Serovars D-K cause urethritis/cervicitis, which may be asymptomatic or cause discharge, but not typically painful ulcers. Serovars L1-L3 cause lymphogranuloma venereum (LGV), which starts with a painless papule/ulcer and progresses to painful suppurative lymphadenopathy.

• (E) Klebsiella granulomatis: Causes donovanosis (granuloma inguinale), which presents with beefy-red, painless, granulomatous ulcers that bleed easily. Diagnosis is made by identifying Donovan bodies within histiocytes.

Management:

• First-line: Oral antiviral therapy (e.g., acyclovir, valacyclovir, famciclovir) to reduce symptom duration and viral shedding.

• Supportive care: Analgesics, saline baths, and topical lidocaine for pain relief.

• Counseling: Education about the chronic nature of the infection, transmission risk (even during asymptomatic shedding), and need for safer sex practices.

Prognosis:
Primary infections resolve within 2-3 weeks. Recurrent outbreaks are common but often decrease in frequency and severity over time. Antiviral therapy can suppress recurrences.