Infectious Disease · Viral Infections
The facts most likely to be tested
Herpes Zoster presents as a painful, unilateral vesicular eruption in a dermatomal distribution that does not cross the midline.
Hutchinson sign, characterized by vesicles on the tip of the nose, indicates involvement of the nasociliary branch of the trigeminal nerve and necessitates urgent ophthalmology referral to prevent herpes zoster ophthalmicus.
Postherpetic neuralgia, defined as pain persisting for >90 days after the onset of the rash, is the most common complication and is treated with gabapentin, pregabalin, or tricyclic antidepressants.
Antiviral therapy (e.g., valacyclovir) is most effective when initiated within 72 hours of symptom onset to reduce the duration of viral shedding and the risk of complications.
The recombinant zoster vaccine (Shingrix) is the preferred preventative measure and is indicated for all adults ≥50 years old, regardless of prior history of shingles or receipt of the older live-attenuated vaccine.
Ramsay Hunt syndrome (herpes zoster oticus) presents with the triad of ipsilateral facial paralysis, ear pain, and vesicles in the auditory canal due to reactivation in the geniculate ganglion.
Diagnosis is primarily clinical, but PCR testing of vesicular fluid is the gold standard if the presentation is atypical or the patient is immunocompromised.
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A 68-year-old male presents to the clinic with a 2-day history of a burning sensation on his right forehead, followed by the appearance of a clustered vesicular rash on an erythematous base. Physical examination reveals the rash is confined to the right side of the forehead and does not cross the midline. Notably, there are vesicles present on the tip of his nose. The patient has no history of recent travel or sick contacts.
What is the most appropriate next step in management?
Urgent ophthalmology referral and initiation of oral valacyclovir.
The presence of vesicles on the tip of the nose (Hutchinson sign) indicates involvement of the nasociliary branch of the trigeminal nerve, which places the patient at high risk for sight-threatening herpes zoster ophthalmicus.
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Etiology / Epidemiology
Reactivation of latent VZV in dorsal root ganglia; incidence increases with age >50 and immunocompromise.
Clinical Manifestations
Painful, dermatomal vesicular rash that does not cross the midline; Hutchinson's sign indicates ocular involvement.
Diagnosis
PCR is the gold standard; Tzanck smear shows multinucleated giant cells.
Treatment
Valacyclovir within 72 hours; do not use corticosteroids for postherpetic neuralgia.
Prognosis
Postherpetic neuralgia is the most common complication; risk increases significantly with age >60.
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Epidemiology & Etiology
Caused by reactivation of the varicella-zoster virus (VZV) following primary infection (chickenpox). Primary risk factors include advanced age, HIV/AIDS, malignancy, and immunosuppressive therapy. The virus remains dormant in the sensory nerve ganglia for decades before clinical reactivation.
Pertinent Anatomy
The virus resides in the dorsal root ganglia or cranial nerve ganglia. Reactivation results in viral replication and axonal transport to the skin, manifesting in a specific dermatomal distribution.
Pathophysiology
Cell-mediated immunity wanes over time, allowing viral replication. The virus travels down the sensory nerve to the skin, causing inflammation and necrosis of the epidermis. This process results in the characteristic dermatomal distribution of vesicles.
Clinical Manifestations
Prodromal pain or paresthesia precedes the rash by 2–3 days. The classic presentation is a grouped vesicular eruption on an erythematous base. Hutchinson's sign (lesions on the nasal tip) indicates involvement of the nasociliary branch of the trigeminal nerve, requiring urgent ophthalmology referral to prevent blindness.
Diagnosis
Clinical diagnosis is usually sufficient. PCR is the gold standard for definitive identification. A Tzanck smear of vesicle fluid reveals multinucleated giant cells, though it cannot distinguish VZV from HSV.
Treatment
Initiate Valacyclovir (or Acyclovir) within 72 hours of symptom onset to reduce duration and severity. Corticosteroids are not indicated for routine treatment and do not prevent postherpetic neuralgia. Manage pain with gabapentin or pregabalin for chronic symptoms.
Prognosis
Postherpetic neuralgia (pain persisting >90 days) is the most common complication, occurring in up to 20-30% of patients over age 60. Early antiviral therapy is the primary intervention to reduce the incidence of this chronic pain syndrome.
Differential Diagnosis
Herpes Simplex: usually recurrent, non-dermatomal, smaller vesicles
Contact Dermatitis: pruritic, non-vesicular, history of exposure
Impetigo: honey-colored crusts, non-dermatomal
Bullous Pemphigoid: autoimmune, tense bullae, non-dermatomal
Erysipelas: spreading, warm, erythematous plaque without vesicles