What is Shingles?
Shingles (herpes zoster) is a painful, vesicular skin rash caused by reactivation of the varicella-zoster virus (VZV) that remains dormant in nerve ganglia after a primary chickenpox infection. 1
Pathophysiology
The virus lies dormant in dorsal root ganglia or cranial nerve sensory ganglia after childhood chickenpox, then reactivates when cellular immunity declines. 1 This reactivation occurs most commonly in:
- Adults and elderly individuals when immune surveillance weakens 1
- Immunocompromised patients (HIV, cancer, transplant recipients, those on immunosuppressive therapy) 1
- Patients with conditions like diabetes, rheumatoid arthritis, lupus, or inflammatory bowel disease 1
Clinical Presentation
The hallmark is a unilateral, painful vesicular eruption following a dermatomal distribution. 1 The typical progression includes:
- Prodromal pain that precedes the rash by 24-72 hours (sometimes longer), presenting as burning, tingling, itching, or sharp pain in the affected dermatome 1
- Erythematous macules that rapidly evolve to papules within hours 1
- Vesicles that frequently coalesce and form bullae, appearing as clear fluid-filled clusters 2
- Pustulation and crusting over 4-6 days in healthy hosts, but potentially 7-14 days in immunocompromised patients 1
- Complete healing typically within 2 weeks in immunocompetent individuals 1
Epidemiology and Risk
The lifetime risk is 20-30% in the general population, increasing to 50% in those over age 85. 1 Key epidemiologic facts:
- Incidence ranges from 1.2 to 4.8 cases per 1,000 person-years in Western populations 1
- Risk increases markedly beginning at approximately 50 years of age 3
- The rash follows dermatomal patterns, most commonly thoracic dermatomes, with foot involvement representing a minority of cases 3
Serious Complications
Potentially debilitating complications significantly impact quality of life and include: 1
- Postherpetic neuralgia (PHN): Pain persisting more than 3 months after rash resolution, which can be highly debilitating 4
- Herpes zoster ophthalmicus: Ocular involvement requiring ophthalmology referral due to risk of vision loss 4
- Bacterial superinfections of the vesicular lesions 1
- Cranial and peripheral nerve palsies 1
- Visceral involvement in severely immunocompromised patients 1
- Chronic ulcerations with persistent viral replication in immunocompromised hosts without adequate treatment 1
Prevention Through Vaccination
Vaccination is the most effective strategy to prevent shingles and its complications. 1 Two vaccines are available:
- Recombinant zoster vaccine (Shingrix): A 2-dose inactivated subunit vaccine recommended for adults ≥50 years and immunocompromised adults ≥18 years, with 97.2% efficacy 1, 2
- Zoster vaccine live (Zostavax): A single-dose live attenuated vaccine for adults 50-79 years, but contraindicated in immunocompromised patients due to risk of disseminated disease 1
Treatment Principles
Antiviral therapy should be initiated within 72 hours of rash onset for maximum benefit. 4 Treatment options include:
- High-dose IV acyclovir: Remains the treatment of choice for immunocompromised hosts 1
- Oral antivirals (acyclovir, valacyclovir, famciclovir): Appropriate for immunocompetent patients or mild cases 1, 5, 6
- Pain management: May require narcotics, tricyclic antidepressants, anticonvulsants, capsaicin, or lidocaine patches for acute pain and PHN 4
Critical caveat: Treatment initiated more than 72 hours after rash onset has limited data supporting effectiveness, emphasizing the importance of early recognition and prompt initiation of therapy. 5, 6