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.
Try two board-style Herpes Zoster questions
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Question 1Infectious DiseaseMedium
A 35-year-old immunocompetent man presents with a painful vesicular rash in the T5-T6 dermatomal distribution on his left chest that does not cross the midline. He reports significant burning pain that started 3 days before the rash appeared. Which of the following is the most likely diagnosis?
AHerpes simplex
BBullous impetigo
CHerpes zoster
DCellulitis
EContact dermatitis
Reveal answer & full explanation
Correct answer: C — Herpes zoster
AHerpes simplex
BBullous impetigo
CHerpes zoster✓
DCellulitis
EContact dermatitis
Why Herpes zoster is correct
Herpes zoster is varicella-zoster virus (VZV) reactivation from a dorsal root or cranial nerve ganglion after primary varicella.
Classic features are a painful, grouped vesicular rash in a single dermatome that does not cross the midline.
A prodrome of burning or neuritic pain typically precedes the rash by 2-3 days, exactly as described here.
Antiviral therapy started within 72 hours of rash onset (valacyclovir 1000 mg TID or famciclovir 500 mg TID for 7 days) shortens the course and reduces complications.
Postherpetic neuralgia (pain persisting more than 3 months) is the most common complication; risk rises with age and immunosuppression and is treated with gabapentin, pregabalin, TCAs, or lidocaine patches.
Why the others are wrong
Contact dermatitis — Produces symmetric, non-dermatomal eczematous patches at sites of allergen contact; confused-with because both cause vesicles, but it never respects a single dermatome or the midline.
Bullous impetigo — Superficial staphylococcal infection with flaccid bullae and honey-colored crusting; confused-with vesicular disease, but it is not dermatomal and lacks the neuritic prodrome.
Cellulitis — Poorly demarcated warm erythema without vesicles; right-concept-wrong-setting, as it is a spreading dermal infection rather than a banded vesicular eruption.
Herpes simplex — also causes grouped vesicles on an erythematous base, sometimes after a tingling or burning prodrome, but recurrences favor the lips or genitals, involve a small patch, and return to the same site; a band of vesicles along a thoracic dermatome after 3 days of neuritic pain is VZV reactivation (confused-with the other herpesvirus vesicular eruption).
Additional high-yield points
Systemic corticosteroids are NOT routine therapy for herpes zoster; they may modestly reduce acute pain but do NOT reduce the risk of postherpetic neuralgia and are not recommended for prophylaxis against it.
The recombinant zoster vaccine (RZV/Shingrix), 2 doses 2-6 months apart, is recommended for all immunocompetent adults 50 and older, and is also recommended for immunocompromised adults beginning at age 19.
RZV is preferred and can be given to immunocompromised patients because it is non-live (recombinant), with efficacy over 90% in immunocompetent adults.
Question 2DermatologyMedium
A 72-year-old has a painful dermatomal vesicular rash on the right chest. Which of the following complications is most likely?
ABacterial superinfection of the vesicles
BPneumonitis from varicella-zoster virus
CSegmental motor paresis of truncal muscles
DPostherpetic neuralgia in the dermatome
EDisseminated zoster across multiple dermatomes
Reveal answer & full explanation
Correct answer: D — Postherpetic neuralgia in the dermatome
ABacterial superinfection of the vesicles
BPneumonitis from varicella-zoster virus
CSegmental motor paresis of truncal muscles
DPostherpetic neuralgia in the dermatome✓
EDisseminated zoster across multiple dermatomes
Why Postherpetic neuralgia in the dermatome is correct
Herpes zoster results from varicella-zoster reactivation in a sensory ganglion, here the thoracic dermatome.
Postherpetic neuralgia in the dermatome is the most common complication overall and its risk rises sharply with older age, as in this 72-year-old.
Early antiviral therapy reduces acute pain and speeds healing, but it has not been shown to reliably reduce the incidence of postherpetic neuralgia; recombinant zoster vaccination is the proven way to prevent it.
Why the others are wrong
Bacterial superinfection of the vesicles — Secondary Staphylococcus aureus or group A streptococcal infection of the lesions can occur, but it is much less common than postherpetic neuralgia in an older adult.
Segmental motor paresis of truncal muscles — Motor involvement of the matching myotome is an uncommon zoster complication that affects only a small minority of patients and usually recovers, so it is far less likely than postherpetic neuralgia.
Disseminated zoster across multiple dermatomes — Dissemination mainly occurs in immunocompromised hosts and is far less common than postherpetic neuralgia in an otherwise healthy older adult.
Pneumonitis from varicella-zoster virus — pneumonia is the classic serious complication of primary varicella in adults, and a chest rash can make lung involvement seem likely, but in zoster, VZV pneumonitis occurs mainly with visceral dissemination in immunocompromised hosts and is far less likely than postherpetic neuralgia in a 72-year-old.
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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) as adjuncts for acute neuritic pain (evidence that they prevent PHN is insufficient)
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
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; antivirals speed healing and reduce acute pain, but evidence that they reduce PHN incidence is weak (Cochrane 2014: oral acyclovir does not; data for valacyclovir/famciclovir are insufficient); recombinant zoster vaccination prevents both zoster and PHN
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.
Gabapentin/pregabalin are used for acute neuritic pain and treat established PHN, but they have not been shown to prevent PHN when started during acute zoster; recombinant zoster vaccination is the proven way to prevent PHN.
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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