shingles (zoster)

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Shingles is an acute, unilateral, self-limiting inflammatory disease of cerebral ganglia and the ganglia of posterior nerve roots and peripheral nerves in a segmented distribution, caused by Varicella Zoster virus (VZV) - the chicken pox virus.

Prodromal symptoms that herald HZ include pruritus, dysesthesia, and pain along the distribution of the involved dermatome

  • this pre-eruptive pain may precede the rash by several days and may be mistaken for myocardial infarction, biliary or renal colic, pleurisy, dental pain, glaucoma, duodenal ulcer, or appendicitis, leading to misdiagnosis and potentially mistreatment
  • in rare instances, the nerve pain is not accompanied by a skin eruption, a condition known as zoster sine herpete (1)

Herpes zoster (HZ) or shingles is a painful condition caused by reactivation of the Varicella Zoster virus (VZV) within the dorsal root or cranial nerve ganglia (1,2)

  • the primary infection which causes varicella (chicken pox) results in
    • migration of the virus from skin lesions to spinal and cranial sensory ganglia where it becomes dormant
    • the development of VZV specific humoral and cell-mediated immunity (3)

  • reactivation of the virus occurs when the cell mediated immunity wanes (1)

  • following reactivation, the virus spreads thorough the affected sensory nerve, causing neuronal damage and reach the corresponding dermatome in the skin where a vesicular rash develops (3)

VZV (not HZ) can be transmitted to seronegative contact by an individual with HZ.

  • it is less contagious than varicella - household transmission rate of HZ (to cause varicella) is 15% (3)

HZ usually occurs only once in life. Around 4-5% of patients may experience a recurrence (4).

Classic skin findings are grouped vesicles on a red base in a unilateral, dermatomal distribution.

  • however, the lesions of HZ progress through stages, beginning as red macules and papules that, in the course of 7 to 10 days, evolve into vesicles and form pustules and crusts. Complete healing may take more than 4 weeks (5)
    • key clinical feature of shingles is a dermatomal eruption of vesicles often preceded by pain and paraesthesia by several days. Erythema precedes the development of vesicles. The vesicles may become pustular 2-3 days following eruption. A tender lymphadenopathy (local) is common in the early stages of the rash. There is increased itching and burning. The affected area may remain depigmented and often it is hypoalgesic.
  • sites affected:
    • most commonly, the lower thoracic region
    • ophthalmic division of the trigeminal nerve
    • occasionally motor nerves, causing paralysis - for example facial paralysis in Ramsay Hunt syndrome, or urinary retention

Disseminated HZ occurs primarily in immunocompromised patients; it usually presents with a dermatomal eruption followed by dissemination but may also present with a diffuse varicella-like eruption (5)

Complications are seen in 13-40% of patients.

  • postherpetic neuralgia (PHN) is the commonest complication
    • incidence of PHN is generally estimated to be between 10 and 20% of cases of HZ (up to 30% in the elderly)
      • 80% of all PHN cases are reported in patients over the age of 50 years (4)

Click here for example images of this condition

Herpes zoster lesions contain high concentrations of VZV, which can be spread by contact and by the airborne route and which can cause primary varicella in exposed, susceptible persons. Less contagious than primary varicella, HZ is only contagious after the rash appears and until the lesions crust. Risk of transmission is reduced further if lesions are covered

  • N.B. Shingles is not as infectious as chicken pox; but people who have not had chicken pox may get chicken pox as a result of contact with a person with shingles.

Key points (6):

  • Shingles:
    • treat if >50 years (post herpatic neuralgia rare if <50 years) and within 72 hours of rash or if 1 of the following:
      • active ophthalmic;
      • Ramsey Hunt; eczema;
      • non-truncal involvement;
      • moderate or severe pain;
      • moderate or severe rash
  • shingles treatment if not within 72 hours:
    • consider starting antiviral drug up to 1 week after rash onset if
      • high risk of severe shingles or continued vesicle formation;
      • older age;
      • immunocompromised;
      • or severe pain

Reference:

Last edited 07/2021 and last reviewed 07/2021

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