Dermatology · PANCE / PANRE

Herpes Zoster (Shingles)

Reactivation of latent VZV in a dorsal root ganglion → painful unilateral dermatomal vesicular eruption.

Also known as: herpes zoster, shingles, zoster, postherpetic neuralgia, zoster ophthalmicus

Overview

Reactivation of varicella-zoster virus (VZV) latent in dorsal root or cranial nerve ganglia, producing a painful unilateral vesicular eruption confined to one or two adjacent dermatomes.

Epidemiology

Lifetime risk ~30% in the US; incidence rises sharply after age 50. ~1 million US cases annually. Increased severity, duration, and risk of postherpetic neuralgia (PHN) with age and immunosuppression.

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Risk factors

Age >50 (declining cell-mediated immunity)
Immunosuppression: HIV, malignancy (especially hematologic), transplant, chemotherapy, biologics, chronic corticosteroids
Stress, trauma
Female sex (slightly higher risk)
Family history of zoster

Pathophysiology

Primary varicella infection establishes lifelong latency in sensory ganglia. Decline in VZV-specific cell-mediated immunity allows reactivation → viral replication in ganglion → axonal transport down sensory nerve → cutaneous vesicular eruption in dermatomal distribution. Neural damage produces acute neuritis and, in some, chronic postherpetic neuralgia.

Clinical presentation

Symptoms

Prodromal pain, burning, paresthesia in dermatomal distribution 1-5 days (occasionally weeks) before rash
Acute neuritic pain — sharp, burning, lancinating, allodynia
Malaise, low-grade fever, headache
Pruritus, tingling in affected area

Signs / physical exam

Unilateral grouped vesicles on erythematous base in a dermatomal distribution — does NOT cross midline (except small overlap)
Most common dermatomes: thoracic (T3-L2), trigeminal (especially V1 — ophthalmic), cervical, lumbar
Lesions progress: erythematous macules/papules → vesicles → pustules → crusts over 7-10 days; complete healing 2-4 weeks (longer in elderly)
Zoster ophthalmicus (V1): involvement of forehead, upper eyelid, tip of nose (Hutchinson sign = nasociliary nerve = high risk of ocular involvement)
Ramsay Hunt syndrome (CN VII + VIII): facial palsy + vesicles in ear canal/auricle + vertigo + hearing loss + ageusia
Disseminated zoster: >20 lesions outside primary dermatome, especially in immunocompromised
Zoster sine herpete: dermatomal pain without rash — diagnosis of exclusion, PCR confirms

Classic findings

Painful unilateral vesicular rash respecting the midline in a dermatomal distribution.

Differential diagnosis

Herpes simplex (zosteriform HSV) — Recurrent vesicles in fixed location, not strictly dermatomal; PCR/culture differentiates
Contact dermatitis — Geometric/linear borders match contactant; pruritus dominant; no prodromal pain
Cellulitis — Diffuse warmth, erythema, no vesicles or dermatomal distribution
Impetigo — Honey-colored crusts, not dermatomal
Bullous pemphigoid — Tense bullae on urticarial base, widespread, older adult; DIF positive
Cardiac ischemia or appendicitis (prodromal pain) — Pain without rash in early prodrome can mimic visceral disease; rash emerges 1-5 days later

Diagnostic workup

Diagnostic criteria

Clinical: prodromal pain + unilateral dermatomal vesicular rash; PCR confirms in atypical cases.

Labs

Clinical diagnosis sufficient in most cases
PCR of vesicle fluid (most sensitive and specific; preferred when confirmation needed)
Direct fluorescent antibody (DFA) — rapid
Tzanck smear shows multinucleated giant cells (does not distinguish HSV from VZV)
Viral culture (low yield)
HIV testing in young adults with zoster
Workup for underlying malignancy not routinely indicated in immunocompetent adults but consider in disseminated or recurrent disease

Imaging

Slit-lamp examination by ophthalmology for any V1 involvement
MRI brain if encephalitis, myelitis, or stroke (varicella vasculopathy) suspected

Diagnostic algorithm

Scenario	Key Management Step
Standard zoster <72 h	Valacyclovir 1 g TID × 7 d + analgesia
Hutchinson sign / V1 involvement	Antiviral + urgent ophthalmology
Ramsay Hunt (CN VII)	Antiviral + prednisone taper + ENT/audiology
Immunocompromised / disseminated	IV acyclovir + airborne/contact isolation
Postherpetic neuralgia	Gabapentin/pregabalin, lidocaine patch, TCA
Prevention	Recombinant zoster vaccine (Shingrix) 2 doses, age ≥50

Herpes zoster scenario-based management.

Treatment

First-line

Antiviral therapy within 72 hours of rash onset (still beneficial if vesicles still forming or in immunocompromised): valacyclovir 1 g PO TID × 7 days, OR famciclovir 500 mg PO TID × 7 days, OR acyclovir 800 mg PO 5x/day × 7-10 days (valacyclovir/famciclovir preferred due to better bioavailability and dosing)
Renal dose adjustment for all antivirals
Pain control: acetaminophen, NSAIDs for mild; gabapentin or pregabalin titrated up for moderate-severe neuritic pain; opioids short-term if needed (codeine, tramadol, oxycodone)
Tricyclic antidepressants (nortriptyline, amitriptyline) for acute pain and PHN prevention
Local: cool compresses, calamine lotion, topical lidocaine 5% patch (after lesions crust)
Vaccination: recombinant zoster vaccine (Shingrix) — 2 doses 2-6 months apart, age ≥50, including those with prior zoster (wait until acute episode resolves)

Zoster ophthalmicus

Same antiviral as above PLUS urgent ophthalmology referral within 24 hours
IV acyclovir if sight-threatening keratitis, iritis, retinal involvement
Topical antivirals and steroids only under ophthalmology direction

Ramsay Hunt syndrome

Antiviral + oral corticosteroid (prednisone 60 mg/day tapered over 1-2 weeks) — improves facial nerve recovery
ENT referral; audiometry

Disseminated / immunocompromised

IV acyclovir 10 mg/kg q8h until clinical improvement, then PO antiviral to complete 14 days
Airborne + contact isolation (disseminated disease can transmit varicella to non-immune contacts)

Postherpetic neuralgia

First-line: gabapentin or pregabalin titrated to effect; topical lidocaine 5% patch; topical capsaicin 8% patch
Second-line: TCAs (nortriptyline, amitriptyline), SNRIs (duloxetine, venlafaxine)
Third-line: opioids, intrathecal corticosteroids, nerve blocks

Second-line / adjunct

Systemic corticosteroids — controversial for typical zoster; may speed acute pain resolution but do not prevent PHN; useful in Ramsay Hunt and severe cases
Recombinant zoster vaccine (Shingrix) recommended for immunocompromised adults ≥19 years per CDC ACIP 2022

Complications

Postherpetic neuralgia (PHN) — pain persisting >90 days after rash onset; affects 10-18% of all zoster patients, ~30% of those >80 years; antiviral therapy reduces but does not eliminate risk
Bacterial superinfection of skin lesions
Zoster ophthalmicus: keratitis, uveitis, scleritis, acute retinal necrosis, secondary glaucoma, vision loss
Ramsay Hunt syndrome: facial palsy (worse prognosis than Bell's palsy), hearing loss, vertigo
CNS: meningoencephalitis, myelitis, varicella vasculopathy → stroke
Disseminated visceral zoster (pneumonitis, hepatitis) in immunocompromised
Motor zoster (segmental muscle weakness)
Transmission of varicella to non-immune contacts (especially neonates, pregnant women, immunocompromised) from active lesions

PANCE pearls

Hutchinson sign (vesicles on tip of nose) predicts ocular involvement in zoster ophthalmicus — urgent ophthalmology referral.
Antiviral therapy is most effective if started within 72 hours of rash onset, but still consider in ongoing vesicle formation, ocular involvement, immunocompromised, or severe pain.
Recombinant zoster vaccine (Shingrix) is preferred over the older live attenuated vaccine (no longer marketed in the US) and is recommended for all adults ≥50 and immunocompromised adults ≥19.
Zoster in a young adult should prompt HIV testing.
Pre-emptive gabapentin/pregabalin within the first weeks of acute zoster may reduce the incidence and severity of postherpetic neuralgia.

References

CDC ACIP 2022 — Use of Recombinant Zoster Vaccine in Immunocompromised Adults Aged ≥19 Years (Anderson et al., MMWR 2022)
AAFP 2017 — Herpes Zoster and Postherpetic Neuralgia: Prevention and Management (Saguil et al., Am Fam Physician 2017)
Cochrane 2014 — Antiviral Treatment for Preventing Postherpetic Neuralgia (Chen et al., Cochrane Database Syst Rev 2014)

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