Varicella vs Herpes zoster
How to tell Varicella and Herpes zoster apart when a board question makes them look alike.
Varicella is primary diffuse multi-stage rash; zoster is reactivation with painful unilateral dermatomal vesicles.
Side by side
Varicella is primary VZV infection with diffuse pruritic vesicles in different stages of healing, fever, and high contagiousness.
Herpes zoster is reactivation of latent VZV with painful unilateral dermatomal grouped vesicles and risk of postherpetic neuralgia.
Primary VZV spreads systemically after respiratory transmission, causing generalized viremia and rash.
Latent VZV reactivates from dorsal root or cranial nerve ganglia and travels along a sensory dermatome.
Centripetal rash, crops of vesicles/macules/papules/crusts at different stages, exposure without immunity, and VZV PCR support varicella.
Unilateral dermatomal pain, grouped vesicles, older age or immunosuppression, ophthalmic involvement, and VZV PCR support zoster.
The trap
Both are VZV (varicella-zoster virus), but they represent very different stages of the same infection. PRIMARY varicella (chickenpox) is acquired by respiratory droplet or direct contact, with a generalized polymorphic rash going through macule, papule, vesicle, pustule, crust stages SIMULTANEOUSLY across all stages on the body (the dewdrops-on-a-rose-petal description), starting on trunk and spreading centrifugally, with fever and constitutional symptoms; complications include secondary bacterial superinfection and rare varicella pneumonia in adults. REACTIVATION zoster (shingles) is reactivation of latent VZV in dorsal root ganglia, presenting as a UNILATERAL DERMATOMAL band of painful vesicles (pain often precedes rash by days), classic in older adults and immunocompromised; high-yield complication is post-herpetic neuralgia (treat acute zoster with valacyclovir or acyclovir within 72 hours of rash onset to reduce PHN risk); ophthalmic zoster (V1 trigeminal distribution with Hutchinson sign on the tip of the nose) warrants urgent ophthalmology consult; Ramsay Hunt syndrome is zoster of the geniculate ganglion with facial palsy plus vesicles in the ear canal.
The repair move
For VZV, ask whether the rash is generalized primary infection or localized dermatomal reactivation.
Try a free question
CoreA child has fever and a diffuse intensely pruritic rash with macules, papules, vesicles, and crusts all present at the same time. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Varicella. Diffuse pruritic vesicular rash with lesions in multiple stages supports primary varicella.
Why the other choices are tempting
- B. Herpes zoster is painful unilateral dermatomal reactivation.
- C. HSV-2 classically causes genital vesicles/ulcers.
- D. Measles causes cough, coryza, conjunctivitis, Koplik spots, and morbilliform rash.
- E. Hand-foot-mouth disease causes oral lesions and hand/foot vesicles.
Flashcards
Tap a card to flip it.
What rash pattern supports varicella?
Diffuse pruritic lesions in different stages of healing support varicella.
What rash pattern supports zoster?
Painful unilateral dermatomal grouped vesicles support herpes zoster.
Quick answers
What is the fastest way to tell Varicella from Herpes zoster?
Varicella is primary diffuse multi-stage rash; zoster is reactivation with painful unilateral dermatomal vesicles.
What is the key clue for Varicella?
Varicella is primary VZV infection with diffuse pruritic vesicles in different stages of healing, fever, and high contagiousness.
What is the key clue for Herpes zoster?
Herpes zoster is reactivation of latent VZV with painful unilateral dermatomal grouped vesicles and risk of postherpetic neuralgia.
What is the common trap with Varicella vs Herpes zoster?
Both are VZV (varicella-zoster virus), but they represent very different stages of the same infection. PRIMARY varicella (chickenpox) is acquired by respiratory droplet or direct contact, with a generalized polymorphic rash going through macule, papule, vesicle, pustule, crust stages SIMULTANEOUSLY across all stages on the body (the dewdrops-on-a-rose-petal description), starting on trunk and spreading centrifugally, with fever and constitutional symptoms; complications include secondary bacterial superinfection and rare varicella pneumonia in adults. REACTIVATION zoster (shingles) is reactivation of latent VZV in dorsal root ganglia, presenting as a UNILATERAL DERMATOMAL band of painful vesicles (pain often precedes rash by days), classic in older adults and immunocompromised; high-yield complication is post-herpetic neuralgia (treat acute zoster with valacyclovir or acyclovir within 72 hours of rash onset to reduce PHN risk); ophthalmic zoster (V1 trigeminal distribution with Hutchinson sign on the tip of the nose) warrants urgent ophthalmology consult; Ramsay Hunt syndrome is zoster of the geniculate ganglion with facial palsy plus vesicles in the ear canal.