Herpes zoster (shingles)

Definition

Herpes zoster (shingles) is the endogenous reactivation of varicella-zoster virus (VZV, human herpesvirus 3), which persists for life in spinal or cranial nerve ganglia after chickenpox. It is characterized by a unilateral vesicular rash confined to one or a few dermatomes and often severe pain. Zoster can occur only in people with prior VZV infection.

Classification

• Segmental zoster: usually thoracic or lumbar (most often dermatomes T3 to L3).
• Herpes zoster ophthalmicus: involvement of the first trigeminal division (V1).
• Herpes zoster oticus (Ramsay Hunt syndrome): involvement of the geniculate ganglion.
• Maxillary zoster, genital zoster, intraoral zoster.
• Disseminated zoster: no longer confined to segments, involving further skin areas and internal organs, mainly in immunodeficiency.

Occurrence & epidemiology

• The cumulative incidence worldwide is about 2.9 to 19.5 cases per 1,000 people; the lifetime risk is about 32 %.
• Frequency rises markedly with age, especially after 50 years; about one in two people who reach 85 years has had zoster.
• Up to 6 % have another episode, more often in immunodeficiency.

Aetiopathogenesis

• Pathogen: varicella-zoster virus, an alphaherpesvirus; chickenpox is the primary infection, zoster is the reactivation after a usually long latency.
• Pathogenesis: reactivation causes inflammation of the sensory ganglion, the skin of the corresponding dermatome and sometimes the anterior and posterior horns, meninges and nerve roots.
• Risk factors: older age, HIV infection and other disorders of cell-mediated immunity (e.g. immunosuppressive drugs), autoimmune diseases, female sex, chronic diseases such as diabetes, asthma and COPD, recent trauma. Zoster also occurs in younger immunocompetent people and in children.
• Transmission: only the virus-containing vesicle fluid is infectious (direct or indirect contact), so contagiousness is low. Infectious from the appearance of the rash until all lesions have crusted, usually 5–7 days. Nonimmune people who become infected develop chickenpox, not zoster.

Clinical features

Symptoms

• Prodrome: burning, stabbing or dysesthetic pain in the affected area, usually 2–3 days before the rash.
• Rash: grouped vesicles on an erythematous base in one or more adjacent dermatomes, unilateral and not crossing the midline; occasional satellite lesions are possible. New lesions form for about 3–5 days, followed by crusting. The skin is often hyperesthetic.
• Herpes zoster ophthalmicus: pain and vesicles on the forehead and around the eye; vesicles on the tip of the nose (Hutchinson sign) indicate involvement of the nasociliary nerve and a higher risk of severe ocular involvement, although the eye may be affected without this sign.
• Herpes zoster oticus: ear pain, vesicles in the external auditory canal, peripheral facial palsy, sometimes vertigo and loss of taste in the anterior two-thirds of the tongue.

Complications

• Postherpetic neuralgia: pain persisting for more than 3 months after the last lesion has crusted; especially in older adults, sometimes for years.
• Disseminated zoster with hematogenous spread in immunodeficiency, potentially life-threatening.
• CNS: meningeal irritation, meningoencephalitis; rarely granulomatous angiitis with contralateral hemiparesis or ascending myelitis.
• Eye: severe ocular involvement in herpes zoster ophthalmicus.

Diagnosis

• Clinical diagnosis: the dermatomal rash is virtually pathognomonic; with typical segmental pain, zoster may be suspected even before the rash appears.
• Pathogen detection in unclear or atypical presentations (e.g. immunodeficiency, CNS involvement): VZV PCR of vesicle fluid, cerebrospinal fluid, bronchoalveolar lavage or EDTA blood; antigen detection by direct immunofluorescence; viral culture is laborious and insensitive.
• Tzanck test: multinucleated giant cells confirm a herpesvirus infection but do not distinguish between VZV and herpes simplex.
• Serology: VZV IgA is highly informative in zoster, IgM may be absent; IgG avidity distinguishes primary infection from reactivation. With CNS involvement, antibody and PCR testing of cerebrospinal fluid.
• Distinction from herpes simplex: herpes simplex recurs more often and does not follow a dermatome.

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Further reading (open access)

1. RKI-Ratgeber: Windpocken (Varizellen), Gürtelrose (Herpes zoster)
2. MSD Manual Professional: Herpes Zoster

Cross-references