Herpes Zoster — USMLE Step 2 CK Guide 2026

About This Page

This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.

Key points

Shingles = VZV reactivation from dorsal root or cranial nerve ganglia
Classic rash: painful grouped vesicles on erythematous base in a unilateral dermatomal distribution that usually does not cross midline
Start valacyclovir, famciclovir, or acyclovir ideally within 72 hours of rash onset; treat later if new lesions, severe disease, ophthalmic involvement, or immunocompromise
Herpes zoster ophthalmicus = V1 distribution; Hutchinson sign on nose predicts ocular involvement and needs urgent ophthalmology
Prevention: recombinant zoster vaccine (Shingrix) for adults >=50 and immunocompromised adults >=19

Overview

Herpes zoster results from reactivation of varicella-zoster virus that remained latent after primary varicella infection. Viral replication causes neuritis and a vesicular eruption in the affected sensory dermatome. Pain often precedes the rash by days, which can mimic myocardial infarction, renal colic, cholecystitis, or radiculopathy depending on dermatome. The major morbidity is postherpetic neuralgia, especially in older adults. In immunocompromised patients, zoster may disseminate and become life-threatening.

Epidemiology

Lifetime risk of shingles is roughly 1 in 3 in the United States and increases with age as VZV-specific cellular immunity wanes. Risk factors include older age, immunosuppression, HIV, malignancy, transplant, systemic corticosteroids, biologic therapy, and stress or illness. Herpes zoster can occur in younger adults, but recurrent, multidermatomal, disseminated, or severe disease should prompt evaluation for immunocompromise.

Clinical Features

Symptoms

Prodromal burning, tingling, itching, or lancinating pain in a unilateral dermatome

Painful vesicular rash developing 1-5 days after prodrome

Fever, malaise, headache, or photophobia may occur

Eye pain, red eye, decreased vision, or V1 facial rash

Widespread lesions beyond primary dermatome or severe systemic symptoms in immunocompromised patient

Signs

Grouped vesicles on erythematous base in unilateral dermatomal distribution

Lesions evolve from papules to vesicles to pustules to crusts over 7-10 days

Hutchinson sign: vesicles on tip/side of nose from nasociliary branch involvement

Ramsay Hunt syndrome: ear vesicles, facial paralysis, hearing symptoms, vertigo

New lesions in multiple dermatomes or diffuse varicella-like eruption suggests disseminated zoster

Investigations

First-line

Clinical diagnosisTypical painful unilateral dermatomal vesicular eruption is diagnostic

Assess immune status and complicationsAge, pregnancy, HIV risk, transplant, malignancy, immunosuppressive medications, ocular/otic/neurologic symptoms

Second-line

VZV PCR from lesion swabMost useful confirmatory test when presentation is atypical, disseminated, vaccine-strain concern, or immunocompromised

HIV testingConsider in young, recurrent, disseminated, multidermatomal, or unusually severe zoster

Specialist

Ophthalmologic slit-lamp examinationUrgent for V1 zoster, Hutchinson sign, red eye, eye pain, photophobia, or visual symptoms

CSF VZV PCRIf meningitis, encephalitis, myelitis, or vasculopathy suspected

Management

CDC Clinical Overview of Shingles and ACIP zoster vaccine recommendations

Antiviral therapy

Start antiviral within 72 hours when possible: valacyclovir 1 g PO TID, famciclovir 500 mg PO TID, or acyclovir 800 mg PO five times daily for 7 days
Treat beyond 72 hours if new lesions are appearing, pain is severe, patient is older, immunocompromised, or ophthalmic/otic/neurologic complications are possible
Severe immunocompromised or disseminated zoster: IV acyclovir and hospital-level care

Pain control

NSAIDs or acetaminophen for mild pain; short-course opioids may be needed for severe acute neuritis
Neuropathic pain agents: gabapentin, pregabalin, or tricyclic antidepressants for postherpetic neuralgia
Topical lidocaine patches or capsaicin for postherpetic neuralgia in selected patients after lesions heal

Special sites

Herpes zoster ophthalmicus: systemic antivirals immediately plus urgent ophthalmology; do not delay for eye exam
Ramsay Hunt syndrome: antivirals and often corticosteroids under specialist guidance; early treatment improves facial nerve outcomes
Avoid topical steroids in ocular zoster unless directed by ophthalmology

Prevention and infection control

Recombinant zoster vaccine (Shingrix) 2-dose series for adults >=50 and adults >=19 who are immunocompromised or will be immunosuppressed
Cover lesions; avoid contact with pregnant nonimmune people, premature infants, and immunocompromised people until crusted
Localized zoster is spread by direct contact with lesions; disseminated zoster requires airborne/contact precautions in healthcare settings

Complications

Postherpetic neuralgia: Persistent neuropathic pain after rash resolution; risk increases with age and severe acute pain
Herpes zoster ophthalmicus: Keratitis, uveitis, retinitis, vision loss
Ramsay Hunt syndrome: Facial paralysis with ear vesicles and vestibulocochlear symptoms
Disseminated zoster: Visceral involvement in immunocompromised patients
Neurologic disease: Meningitis, encephalitis, myelitis, stroke from VZV vasculopathy
Secondary bacterial infection: Impetigo/cellulitis from excoriated vesicles

USMLE Step 2 CK Exam Tips

1Painful unilateral dermatomal vesicles = shingles
2Treat with antivirals within 72 hours; valacyclovir is easier dosing than acyclovir
3Vesicles on nose tip + V1 rash = Hutchinson sign; urgent ophthalmology
4Ear vesicles + facial paralysis = Ramsay Hunt syndrome
5Persistent burning pain after rash = postherpetic neuralgia; gabapentin/pregabalin/TCA
6Disseminated or multidermatomal zoster in young patient = evaluate immunocompromise/HIV
7Shingrix is recombinant, not live; recommended for >=50 and immunocompromised adults >=19

Put your reading into practice

Checking available topic practice…

Choose USMLE Step 2 CK questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.

Choose USMLE Step 2 CK practice

After your session, return to this section to revisit the reading and choose your next review.

regional clinical guidance