- Microbiology/Pathophysiology
- Family: Herpesviridae (enveloped, double-stranded, linear DNA virus).
- Latency: A key feature. After primary infection, the virus becomes latent in sensory nerve ganglia and can reactivate later.
- HSV-1: Latent in the trigeminal ganglia.
- HSV-2: Latent in the sacral ganglia.
- Histology: Look for Cowdry type A intranuclear inclusions and multinucleated giant cells on a Tzanck smear.
- Clinical Presentations
- Although HSV-1 is classically “above the waist” and HSV-2 is “below the waist,” either type can infect either location.
- HSV-1 Manifestations:
- Gingivostomatitis: Common primary infection in children, causing fever and painful vesicles/ulcers throughout the oral mucosa.
- Herpes Labialis (Cold Sores): Recurrent vesicular lesions on or around the lips.
- Keratoconjunctivitis: Corneal infection that can cause dendritic ulcers visible with fluorescein stain; a major cause of blindness.
- Temporal Lobe Encephalitis: The most common cause of sporadic, fatal encephalitis. Presents with fever, headache, altered mental status, seizures, and personality changes.
- HSV-2 Manifestations:
- Genital Herpes: Causes painful vesicular lesions on the genitals and perineum, often with inguinal lymphadenopathy. Recurrences are more frequent and severe with HSV-2 than with genital HSV-1.
- Aseptic Meningitis: A more common complication with HSV-2 than with HSV-1.
- Other Manifestations (Either HSV-1 or HSV-2):
- Herpetic Whitlow: A painful vesicular infection of the finger, common in healthcare workers or children who suck their thumbs.
- Erythema Multiforme: An acute, immune-mediated condition characterized by “target lesions,” often triggered by a preceding HSV infection.
- Neonatal Herpes: A severe, often life-threatening infection acquired during delivery. It can be localized to the Skin, Eyes, and Mouth (SEM), involve the CNS, or be a disseminated multi-organ disease.
- Diagnosis
- PCR: The gold standard for diagnosis, especially for CNS infections (analyzing CSF) or direct testing of lesions.
- Viral Culture: Can be used to isolate the virus from an active lesion.
- Tzanck Smear: A classic (but less sensitive/specific) test showing multinucleated giant cells and intranuclear inclusions.
- Serology: Detects antibodies and can differentiate between HSV-1 and HSV-2; useful for confirming chronic infection in patients without active lesions.
- Management
- Mechanism: Antivirals like Acyclovir, Valacyclovir, and Famciclovir are guanosine analogs that inhibit viral DNA polymerase.
- Indications:
- Primary Infection: Treatment can shorten the duration and severity of the first outbreak.
- Episodic Therapy: Used to manage recurrent outbreaks.
- Suppressive Therapy: Daily low-dose antiviral medication is used for patients with frequent (e.g., >6 per year) or severe recurrences to reduce their frequency.
- Severe Infections: HSV encephalitis or neonatal herpes requires immediate IV Acyclovir. Untreated HSV encephalitis has a high mortality rate.