Chickenpox and herpes zoster are caused by the varicella-zoster virus (human herpesvirus type 3); chickenpox is the acute, primary infection phase of the virus, and herpes zoster (shingles) represents reactivation of virus from the latent phase.
Herpes zoster inflames the sensory root ganglia, the skin of the associated dermatome, and sometimes the posterior and anterior horns of the gray matter, meninges, and dorsal and ventral roots. Herpes zoster frequently occurs in older and HIV-infected patients and is more frequent and severe in immunocompromised patients because cell-mediated immunity in these patients is decreased. There are no clear-cut precipitants.
Lancinating, dysesthetic, or other pain develops in the involved site, typically followed within 2 to 3 days by a rash, usually crops of vesicles on an erythematous base. The site is usually one or more adjacent dermatomes in the thoracic or lumbar region, although a few satellite lesions may also appear. Lesions are typically unilateral and do not cross the midline of the body. The site is usually hyperesthetic, and pain may be severe. Lesions usually continue to form for about 3 to 5 days.
Herpes zoster may disseminate to other regions of the skin and to visceral organs, especially in immunocompromised patients.
Geniculate zoster (Ramsay Hunt syndrome, herpes zoster oticus) results from involvement of the geniculate ganglion. Ear pain, facial paralysis, and sometimes vertigo occur. Vesicles erupt in the external auditory canal, and taste may be lost in the anterior two thirds of the tongue.
Ophthalmic herpes zoster results from involvement of the gasserian ganglion, with pain and vesicular eruption around the eye and on the forehead, in the V1 distribution of the ophthalmic division of the 5th (trigeminal) cranial nerve. Ocular disease can be severe. Vesicles on the tip of the nose (Hutchinson sign) indicate involvement of the nasociliary branch and a higher risk of severe ocular disease. However, the eye may be involved in the absence of lesions on the tip of the nose.
Intraoral zoster is uncommon but may produce a sharp unilateral distribution of lesions. No intraoral prodromal symptoms occur.
Fewer than 4% of patients with herpes zoster experience another outbreak. However, many patients, particularly older patients, have persistent or recurrent pain in the involved distribution (postherpetic neuralgia), which may persist for months or years or permanently.
The pain of postherpetic neuralgia may be sharp and intermittent or constant and may be debilitating.
Herpes zoster is suspected in patients with the characteristic rash and sometimes even before the rash appears if patients have typical pain in a dermatomal distribution. Diagnosis is usually based on the virtually pathognomonic rash.
If the diagnosis is equivocal, detecting multinucleate giant cells with a Tzanck test can confirm infection, but the Tzanck test is positive with herpes zoster or herpes simplex. Herpes simplex virus (HSV) may cause nearly identical lesions, but unlike herpes zoster, HSV tends to recur and is not dermatomal. Viruses can be differentiated by culture or polymerase chain reaction (PCR). Antigen detection from a biopsy sample can be useful.
Wet compresses are soothing, but systemic analgesics are often necessary.
Treatment with oral antivirals decreases the severity and duration of the acute eruption and the rate of serious complications in immunocompromised patients; it may decrease the incidence of postherpetic neuralgia.
Treatment of herpes zoster should start as soon as possible, ideally during the prodrome, and is less likely to be effective if given > 72 hours after skin lesions appear, especially in the absence of newly forming lesions. Famciclovir 500 mg 3 times a day for 7 days and valacyclovir 1 g 3 times a day for 7 days have better bioavailability with oral dosing than acyclovir, and therefore for herpes zoster, they are generally preferred to oral acyclovir 800 mg 5 times a day for 7 to 10 days. Corticosteroids do not decrease the incidence of postherpetic neuralgia.
For less severely immunocompromised patients, oral famciclovir, valacyclovir, or acyclovir (see above) is a reasonable option; famciclovir and valacyclovir are preferred. For severely immunocompromised patients, acyclovir is recommended at a dosage of 10 to 15 mg/kg IV every 8 hours for 10 to 14 days for adults and 10 to 20 mg/kg IV every 8 hours for 7 days for children < 12 years.
Although data concerning the safety of acyclovir and valacyclovir during pregnancy are reassuring, the safety of antiviral therapy during pregnancy is not firmly established. Because congenital varicella can result from maternal varicella but rarely results from maternal zoster, the potential benefit of treatment of pregnant patients should outweigh possible risks to the fetus. Pregnant patients with severe rash, severe pain, or ophthalmic zoster can be treated with valacyclovir or acyclovir, especially in later stages of pregnancy. There is longer experience with the use of acyclovir in pregnancy as compared to valacyclovir.
A newer recombinant zoster vaccine is recommended for immunocompetent adults ≥ 50 years whether they have had herpes zoster or been given the older, live-attenuated vaccine or not; 2 doses are given 2 to 6 months apart and at least 2 months after the live-attenuated vaccine (for more information, see Recommendations of the Advisory Committee on Immunization Practices for Use of Herpes Zoster Vaccines). The newer, recombinant vaccine appears to provide much better and longer-lasting protection than the older, single-dose, live-attenuated zoster vaccine (which is a higher-dose version of the varicella vaccine). For immunocompetent adults ≥ 60 years, the recombinant vaccine or the live-attenuated vaccine is recommended, but the recombinant vaccine is preferred. Data regarding the efficacy of the recombinant vaccine in immunocompromised patients are emerging, and there are currently no recommendations for its use in immunocompromised patients. The live-attenuated vaccine is contraindicated in immunocompromised patients.
Herpes zoster is caused by reactivation of the varicella-zoster virus (the cause of chickenpox) from its latent phase.
A painful rash, usually crops of vesicles on an erythematous base, develops on one or more adjacent dermatomes.
Fewer than 4% of patients have another outbreak of zoster, but many, particularly older patients, have persistent or recurrent pain for months or years (postherpetic neuralgia).
Antivirals (acyclovir, famciclovir, valacyclovir) are beneficial, especially for immunocompromised patients.
Analgesics are often necessary.
Immunocompetent adults ≥ 50 years should be given recombinant zoster vaccine whether they have had herpes zoster or not.