Varicella and herpes zoster — rash interpretation and management viva

Interpretation

The examiner presents a clinical photograph showing a unilateral, band-like cluster of vesicles over the right T6 dermatome, not crossing the midline, in a 65-year-old man with prodromal burning pain, and asks: "What do you see, what is the diagnosis, and how would you manage this patient?"

• Observation: a painful, unilateral, dermatomal vesicular eruption that does not cross the midline, with all lesions in the affected dermatome at roughly the same stage.
• Diagnosis: herpes zoster (shingles) — reactivation of latent varicella-zoster virus (VZV, human herpesvirus 3) from the T6 dorsal root ganglion.^[1]
• Clinical correlation is mandatory — combine the prodromal dermatomal pain, the typical evolution (erythema → papules → grouped vesicles → pustules → crusts), and the unilateral dermatomal distribution. Vitals and immune status determine severity and route of antiviral.

Key points

The examiner will probe each of these; be ready to defend them at viva depth:

1. Definition and natural history — VZV is a neurotropic alpha-herpesvirus; primary infection = varicella (chickenpox), a generalised vesicular rash in crops at different stages simultaneously (centripetal). The virus then establishes lifelong latency in dorsal root and cranial-nerve ganglia; reactivation = herpes zoster (shingles) when VZV-specific cell-mediated immunity wanes (age, immunosuppression).^[2]
2. Pathophysiology of reactivation — virus replicates in the ganglion (ganglionitis/neuritis → prodromal pain), travels anterograde down the sensory nerve to the dermatome, producing the unilateral dermatomal rash. Destruction of the ganglion and nerve underlies postherpetic neuralgia.
3. Antiviral therapy — within 72 hours of the rash — reduces acute pain, rash duration, viral shedding and postherpetic neuralgia: valaciclovir 1 g TDS or famciclovir 500 mg TDS (or aciclovir 800 mg five times daily) for 7 days. Always treat (regardless of timing) the over-50, ophthalmic, Ramsay Hunt, immunocompromised, or disseminated patient.^[1]
4. IV aciclovir 10 mg/kg every 8 hours for 7–10 days (renal-adjusted, hydrated) — for ophthalmic zoster with ocular involvement, Ramsay Hunt, disseminated/multidermatomal, immunocompromised, CNS disease, varicella pneumonia, neonatal, and severe varicella in pregnancy.^[1]
5. Ophthalmic zoster (V1) — Hutchinson sign (vesicle on tip/side of nose = nasociliary nerve = cornea at risk) = ophthalmology emergency. Topical corticosteroids for uveitis only under ophthalmology supervision; never in active dendritic keratitis.
6. Ramsay Hunt — VZV of the geniculate ganglion (CN VII): ear vesicles + LMN facial palsy + vestibulocochlear symptoms; treat with antiviral + high-dose corticosteroid.
7. Varicella pearls — avoid aspirin (Reye syndrome) and NSAIDs in children; varicella pneumonia (bilateral reticulonodular CXR, may calcify) in adults/pregnant/smokers needs IV aciclovir; cerebellar ataxia is the commonest neurological complication in children.
8. Prevention — live-attenuated varicella vaccine (children, 2 doses); recombinant zoster vaccine (Shingrix) for adults over 50 (over 90% efficacy); VZIG 625 IU IM within 10 days (ideally 96 h) for high-risk susceptible contacts (immunocompromised, pregnant, neonatal).^[2]

References

1. Patil A, et al. Herpes zoster: A Review of Clinical Manifestations and Management. Viruses 2022.^[1]
2. Freer G, Pistello M. Varicella-zoster virus infection: natural history, clinical manifestations, immunity and vaccination strategies. New Microbiologica 2018.^[2]

References2ShowHide

1. [1]Patil A, Goldust M, Wollina U. Herpes zoster: A Review of Clinical Manifestations and Management. Viruses, 2022.PMID 35215786
2. [2]Freer G, Pistello M. Varicella-zoster virus infection: natural history, clinical manifestations, immunity and current and future vaccination strategies. New Microbiologica, 2018.PMID 29498740