Infectious Disease · Sexually Transmitted Infections
The facts most likely to be tested
Primary genital herpes typically presents as painful, grouped vesicles on an erythematous base that progress to shallow, tender ulcers.
The gold standard for diagnosis is PCR testing of the lesion, which is significantly more sensitive than viral culture.
Tzanck smear showing multinucleated giant cells is a classic, though low-sensitivity, diagnostic finding.
First-episode primary infections are frequently associated with systemic symptoms including fever, malaise, and tender inguinal lymphadenopathy.
Acyclovir, valacyclovir, or famciclovir are the first-line treatments for both initial episodes and suppressive therapy.
Asymptomatic viral shedding is common, meaning transmission can occur even in the absence of active lesions.
Cesarean section is indicated for patients with active genital lesions or prodromal symptoms at the time of labor to prevent neonatal herpes.
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A 24-year-old female presents to the clinic complaining of severe vulvar pain and dysuria for the past 3 days. She reports a new sexual partner 2 weeks ago. Physical examination reveals multiple painful, grouped vesicles on an erythematous base involving the labia majora and minora. She also has tender bilateral inguinal lymphadenopathy and a low-grade fever. A swab of the lesion is sent for laboratory analysis.
What is the most appropriate diagnostic test to confirm the suspected diagnosis?
PCR testing of the lesion
The patient's presentation of painful, grouped vesicles on an erythematous base is classic for primary HSV infection, and PCR is the most sensitive and preferred diagnostic method.
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Etiology / Epidemiology
Caused by HSV-2 (most common) or HSV-1; transmitted via direct skin-to-skin contact during viral shedding.
Clinical Manifestations
Presents as painful, grouped vesicles on an erythematous base; prodrome of burning/tingling is common.
Diagnosis
PCR is the gold standard; Tzanck smear shows multinucleated giant cells.
Treatment
Acyclovir is the first-line treatment; must initiate within 72 hours for maximum efficacy.
Prognosis
Lifelong latent infection in sacral ganglia; recurrence is common but typically less severe.
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Epidemiology & Etiology
HSV-2 is the primary cause of genital herpes, though HSV-1 incidence is rising due to oral-genital contact. Transmission occurs via asymptomatic viral shedding even in the absence of active lesions. High-risk groups include those with multiple sexual partners and history of other STIs.
Pertinent Anatomy
The virus establishes latency in the sacral dorsal root ganglia. Reactivation travels down the sensory nerve axons to the dermatomes of the genitalia, perineum, or buttocks.
Pathophysiology
Primary infection involves viral entry through micro-abrasions in the mucosa or skin. The virus replicates locally, causing epithelial cell lysis and inflammation, before migrating to the sensory ganglia for lifelong latency. Recurrences are triggered by stress, UV light, or immunosuppression.
Clinical Manifestations
Primary infection is often severe, presenting with painful, grouped vesicles that ulcerate. Patients may report prodromal symptoms of paresthesia or burning before eruption. Red flags include urinary retention due to sacral nerve involvement or aseptic meningitis.
Diagnosis
PCR is the diagnostic test of choice due to high sensitivity and specificity. A Tzanck smear of the lesion base reveals multinucleated giant cells, though it lacks the sensitivity of PCR. Viral culture is an alternative but is less sensitive than PCR.
Treatment
Acyclovir (or valacyclovir) is the first-line therapy for both primary and recurrent episodes. Avoid sexual contact until lesions have completely re-epithelialized to prevent transmission. Chronic suppressive therapy is indicated for patients with >6 recurrences per year.
Prognosis
Infection is chronic and incurable. Complications include secondary bacterial infection, aseptic meningitis, and increased risk of HIV transmission. Patients require counseling on the risk of asymptomatic shedding.
Differential Diagnosis
Syphilis: painless chancre
Chancroid: painful ulcer with suppurative lymphadenopathy
Lymphogranuloma venereum: transient ulcer followed by inguinal buboes
Behçet syndrome: oral and genital ulcers with uveitis
Contact dermatitis: pruritic, non-vesicular rash