Herpes Zoster/Shingles

Herpes Zoster is caused by the reactivation of the Varicella-Zoster Virus (VZV), which remains latent in the dorsal root ganglia after an initial chickenpox infection.

• Prodrome: Patients almost always report a pre-eruptive phase (prodrome) lasting 1–5 days. This consists of localized pain, tingling, burning, or itching. The pain can be so severe it is sometimes mistaken for a heart attack, pleurisy, or gallstones before the rash appears.

• Distribution: The symptoms are strictly unilateral (affecting only one side of the body) and follow a specific dermatome (a strip of skin supplied by a single spinal nerve).

• Risk Factors: Most common in patients over 50 years old. Other risks include physical stress, illness, or immunosuppression (e.g., HIV, malignancy, or medications like steroids).

• Medical History: A childhood history of chickenpox is a prerequisite.

• The "Dermatomal" Rule: The hallmark of shingles is that the lesions do not cross the midline of the body.

• Morphology: * It begins as erythematous (red) macules and papules.

  • These rapidly evolve into grouped vesicles on an erythematous base.

  • Within 7–10 days, the vesicles become pustular and then crust over.

• Common Sites: The thoracic nerves (chest/back) are most frequently involved, followed by the cranial nerves (face).

• Hutchinson’s Sign: Vesicles on the tip or side of the nose. This is a clinical emergency as it indicates involvement of the ophthalmic division of the trigeminal nerve, risking permanent vision loss.

Crucial Note for Darker Skin Tones

• Erythema Masking: The "red base" may appear violaceous, grayish, or hyperpigmented (dark brown) in darker skin. This can make the early "red patch" stage difficult to identify until the blisters actually appear.

• Post-Inflammatory Hyperpigmentation (PIH): Shingles often leaves behind significant dark staining along the dermatome that can last for many months, which is often as distressing to the patient as the initial rash.

• Keloid Risk: In patients prone to keloids, the deep inflammation of shingles can trigger dermatomal keloid formation as the ulcers heal.

• Differential Diagnosis: Must be distinguished from Phytophotodermatitis (streaky rash from plant juice + sun) which can sometimes look "linear," but will not follow a dermatome or have the same neuralgic pain.

• DermNet NZ – Herpes Zoster: https://dermnetnz.org/topics/herpes-zoster

• StatPearls – Herpes Zoster (2024 update): https://www.ncbi.nlm.nih.gov/books/NBK441824/

• CDC – Shingles Clinical Overview: https://www.cdc.gov/shingles/hcp/clinical-overview.html