An acute eruption caused by a reactivation of latent varicella virus in the dorsal root ganglia of a partially immune host. Herpes zoster may occur at any age, but the peak incidence occurs between ages 50 and 70, and the age-specific incidence increases throughout life. Zoster usually affects otherwise healthy people, but immunosuppressed patients are at higher risk. The increased frequency among older persons may be explained partially by a decrease in cellular immune response to varicella-zoster antigen, which is undetectable in up to 30% of previously immune, healthy persons > 60 yr. Other factors that predispose persons to a reactivation of varicella virus include immunosuppressive drugs, corticosteroids, malignancy, local irradiation, trauma, and surgery. Herpes zoster recurs in about 6% of cases, usually at the same site as the initial episode.
The major difference between herpes zoster in the elderly and in young adults is the incidence of postherpetic neuralgia, which increases sharply with age to about 40% in those > 60 yr. The duration and severity of discomfort increase even more markedly with age than the incidence does. Other complications include encephalitis, ophthalmic disease, motor neuropathies, Guillain-Barre syndrome, and urinary retention.
Symptoms and Signs: The patient may develop prodromal symptoms of chills, fever, malaise, GI disturbance, and paresthesia or pain along the affected dermatome. The distribution of dermatomal zoster infections is 50% to 60% thoracic, 10% to 20% trigeminal, 10% to 20% cervical, 5% to 10% lumbar, and < 5% sacral. Rarely, prodromal symptoms persist for 5 to 7 days, leading to a variety of misdiagnoses from herniated disk to acute abdomen. Usually, red papules appear along a dermatome within 3 days. These eruptions rapidly develop into grouped vesicles, which vary in size, may be hemorrhagic, and may be extremely painful. After about 5 days, the vesicles begin to dry and form scabs; gradual healing occurs over the next 2 to 4 wk. Persistent hyperpigmentation or true scarring may result, particularly in the elderly.
In about 50% of patients with uncomplicated herpes zoster, some vesicles appear outside the affected area. However, if widespread severe dissemination occurs, an underlying lymphoma or other cause of immunodeficiency should be suspected.
Ophthalmic herpes zoster results from involvement of the ophthalmic division of the trigeminal nerve. Conjunctivitis, iridocyclitis, and keratitis may occur. In such cases, an ophthalmologic consultation should be sought. Lesions on the tip of the nose indicate involvement of the nasociliary and ophthalmic nerves. The risk of postherpetic neuralgia is greater than with involvement of other dermatomes.
Geniculate neuralgia (Ramsay Hunt syndrome) results from involvement of the geniculate ganglion. Facial paralysis (usually temporary) occurs, pain develops in the ear on the affected side, and taste is lost in the anterior two thirds of the tongue. Vesicles appear on the soft palate, fauces, and external auditory meatus on the affected side. Consultation with a neurologist is advisable.
Diagnosis: The finding of multinucleate giant cells on a cytologic smear or biopsy of a vesicle confirms the diagnosis. Although not commonly needed, electron microscopy and vesicle fluid culture can also identify the virus. However, false-negative results are common with vesicle fluid culture.
Treatment: A systemic corticosteroid (eg, prednisone 40 to 60 mg/day), started within a week of the eruption, appears to reduce acute symptoms and the risk of postherpetic neuralgia in elderly patients. Corticosteroids are the treatment of choice in patients with geniculate neuralgia (Ramsay Hunt syndrome).
If the patient is seen within 3 days of the onset of the eruption, oral or IV acyclovir is appropriate. This drug inhibits the development of new vesicles and decreases the duration of viral shedding and discomfort. Acyclovir also appears to decrease the risk of postherpetic neuralgia. The recommended oral dosage is 800 mg 5 times daily for 10 days. The IV dosage is 5 mg/kg q 8 h for 5 days.
Analgesia is usually needed, as well. Simple analgesics, such as acetaminophen or aspirin given q 4 h or nonsteroidal anti-inflammatory drugs may be sufficient, but some patients require more potent medication. However, opioids should be avoided if possible, especially in the elderly, because of the increased risks of adverse reactions and medication errors.
Topical treatment consists of soaking the affected areas in Burow’s solution (aluminum acetate 5%), diluted 1:20 to 1:40, to remove vesicle crusts, decrease oozing, and dry and soothe the skin. Gauze dressings are soaked in the solution, applied to the affected areas, and loosely bandaged. The dressings are changed q 2 to 3 h. If impetigo develops, systemic antibiotics should be given (see BACTERIAL INFECTIONS, above).
Until dry crusts appear, herpes zoster lesions contain infectious viral particles. A person who has never had varicella may develop it after direct contact with the lesions or with moist, contaminated dressings. Usually, only young children are susceptible. However, because varicella virus is teratogenic in early fetal development, pregnant women should avoid contact with zoster patients. Severely immunocompromised patients should also avoid exposure. Ordinarily, isolating zoster patients from casual contact with other adults is not necessary, however.