Herpes zoster
Also called shingles
Reactivation of latent varicella-zoster virus in a single sensory ganglion: pain first, then grouped vesicles on an erythematous base in one dermatome, stopping at the midline.
How it looks
Grouped vesicles on an erythematous base in a unilateral T5 dermatomal band on the trunk, with sharp midline cut-off.
Rose is the lesion, grey the pattern the lesions make, green where on the body it lives.
Across skin tones
The erythematous base may be subtle in deeply pigmented skin; the grouped vesicles, unilateral band, and pain carry the diagnosis.
Don't miss
Vesicles on the nasal tip (Hutchinson sign) mark nasociliary involvement, the eye is at risk. Zoster in more than two dermatomes or crossing the midline suggests dissemination: think immunocompromise.
Forms & variants
Herpes zoster ophthalmicus
V1 zoster; vesicles on the nose tip (Hutchinson sign) predict ocular involvement and buy a same-day ophthalmology review.
Disseminated zoster
More than twenty vesicles beyond the primary and adjacent dermatomes, usually in immunocompromise; treat with IV antivirals and isolate as airborne-contagious, like varicella.
Symptoms & course
- Burning or stabbing pain, often preceding the rash by days
- Allodynia in the band
- Itch or tingling prodrome
Diagnostic approach
- Clinical diagnosis in typical cases
- PCR of vesicle fluid when atypical or disseminated
Differential, and how to separate them
- Contact dermatitis
Favours it: Itch over pain, exposure geometry, crosses midline
Against it: Zoster hurts, follows a dermatome, and respects the midline
- Impetigo
Favours it: Honey crust, children, no dermatomal pattern
Against it: Zoster's vesicles are grouped in a painful band
Management principles
- Antivirals ideally within 72 hours of rash onset
- Adequate analgesia, undertreated pain predicts postherpetic neuralgia
- Urgent ophthalmology for V1 involvement
Clinical pearl: Pain in a band before any rash is the classic zoster head-fake, patients get worked up for MI, renal colic, or appendicitis first.
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