HEALTH FROM TRUSTED SOURCES: Herpes zoster

Author: Dr Jack Resneck Jr University of California San Francisco 2008-07-28

Herpes Zoster: A Painful Skin Rash (also known as Shingles or Zoster) Caused by the Varicella Zoster Virus.

Introduction:

Herpes Zoster (also known as shingles or zoster) is a painful skin rash caused by the varicella zoster virus (VZV), the same virus that causes chickenpox. This is a different virus than the one that causes genital herpes and fever blisters (herpes simplex). Zoster was not known to be associated with chickenpox until 1888, and the two diseases were linked to a common virus in the early twentieth century.

After a person is infected with VZV and develops chickenpox, the virus usually remains dormant (or inactive) in nerve cells known as dorsal root and cranial ganglia without causing any symptoms. At some point in the future (often many years later), the virus can travel back down a sensory nerve to the skin, causing the rash of zoster. In its most common form, zoster causes painful blisters limited or near to the skin area associated with a single nerve, usually on just one side of the body. Although the rash usually heals in a few weeks, some patients continue to experience residual pain in the area for months or years, a condition known as post-herpetic neuralgia. Most patients who develop zoster will only have a single episode during their lifetime.

Who Gets Zoster?

Ninety-eight percent of the world’s adults have been exposed to the varicella virus and are therefore at risk of getting zoster. Ten to 20 percent of people who had chickenpox eventually develop zoster, and about 500,000 to 1 million patients per year develop zoster in the US.

Reactivation (the return of the VZV to the skin leading to the rash) may occur spontaneously, but is usually thought to be induced by a temporary or permanent weakness in a patient’s immune system. The majority of cases occur in patients older than 50 years of age or those with a compromised immune system. The risk of developing zoster increases with age, and those over 80 are four times more likely to get the disease than those age 20-50. Patients with cancer (especially leukemia and lymphoma), advanced HIV-infection, and those being treated with medications that suppress the immune system (such as chemotherapy for cancer or drugs taken by patients who received organ transplants) are all at increased risk of developing zoster. Rarely, children (particularly those who had chickenpox during their first year of life or those with the additional risk factors listed above) can also develop zoster. Non-white patients have been reported to have a lower risk of developing zoster than Caucasians.

Is Zoster Contagious?

The rash of zoster cannot be passed from one person to another. However, the varicella zoster virus can indeed be spread from someone with the blistering phase of the rash to another person who lacks immunity to the virus (such as babies who have neither had chickenpox nor been vaccinated against VZV). The newly infected person can then develop chickenpox (not zoster). Once the blisters of the zoster rash have crusted over, a person is usually no longer contagious.

Symptoms of Zoster:

Most cases of zoster begin with intense pain in the affected area of skin that usually lasts one to three days before any rash appears (though it can be more than a week). Patients often describe this pain as having a burning, tingling, or throbbing sensation, and the area can be extremely sensitive to touch. This pain, and the rash that follows, is usually limited to an area of skin associated with a single sensory nerve (known as a dermatome) and the immediate surrounding area. Each dermatome is confined to a single side of the body, so the symptoms rarely cross the midline. While zoster most often involves the trunk, it can also occur on the scalp, face, neck, or an extremity. Occasionally, there may also be fever or headache during the early phase of illness.

In most cases, a rash consisting of red bumps or splotches that rapidly develops numerous blisters appears in the affected area. Because of the shape of most dermatomes (area of skin associated with a single sensory nerve), the rash is often in the shape of a band or stripe that only affects a single side of the body. The pain continues and can intensify during this period. New blisters can continue to appear for a few days. Typically, the blisters turn into white pustules and then form scabs or crust and begin to heal. The entire process usually lasts two to three weeks, but active lesions can persist over one month in elderly patients.

In some atypical cases, patients may experience a zoster rash in the absence of any pain. It is also possible for zoster to present with pain that never develops into a rash.

Complications of Zoster

Zoster of the upper face or nasal tip can involve the eye (ophthalmic zoster). Because there is a risk of permanent damage to the eye, patients with zoster in these areas should be seen on an urgent basis by an ophthalmologist.

Zoster of the ear can lead to Ramsay Hunt syndrome, in which the patient may experience hearing loss, dizziness (vertigo), and sometimes facial paralysis. Rarely, this syndrome can also involve inflammation of cerebral blood vessels leading to a stroke. Patients with Ramsay Hunt syndrome should seek medical attention.

While most cases are confined to a limited area of skin, some patients (particularly those with compromised immune systems) may develop disseminated (or widespread) zoster, defined as more than 20 blisters outside the band of skin associated with a single nerve. These patients may also develop involvement of the lungs and central nervous system. Patients with disseminated zoster should seek medical attention.

In most patients, affected areas of skin heal well, but more severe cases can lead to scarring of the skin. Early treatment with oral antiviral medications (see below) may reduce the likelihood of scarring. Despite lore suggesting that topical Vitamin E and topical antibiotics are useful in the prevention of scar formation, these preparations are no better than ordinary Vaseline. Furthermore, many patients develop allergic reactions to these topical agents.

In about one-third of cases, the pain of zoster can be prolonged for months or years after the rash subsides. This condition, known as post-herpetic neuralgia, occurs in 20% of patients with zoster and can cause debilitating pain. This chronic pain can result in significant disability and profoundly affect patients’ quality of life. Certain patients with zoster have a higher risk of developing post-herpetic neuralgia, including older patients, those with severe rash, severe pain, or disseminated (widespread) rash.

How is Zoster Diagnosed?

Most cases of zoster are straightforwardly diagnosed by physicians without further testing. The early pain symptoms preceding the rash, however, may be confused with numerous other conditions. In some cases, particularly those involving blisters on the genitals, buttocks, or lower face, it can be difficult to differentiate zoster from infection with herpes simplex virus. In these cases, a scraping of cells from the base of a blister can be submitted for a direct fluorescent antibody (DFA) test or for polymerase chain reaction (PCR) testing to determine if either virus is present.

How is Zoster Treated?

Acute attacks of zoster are usually treated with oral antiviral medications (acyclovir, famciclovir, or valacyclovir). If treatment with these agents is initiated within 72 hours of the onset of rash, it can reduce both the severity and duration of pain. Most importantly, these drugs somewhat reduce the likelihood that a patient will develop post-herpetic neuralgia. In severe or complicated cases of zoster, patients are sometimes admitted to the hospital and treated with intravenous acyclovir.

The addition of corticosteroids (such as oral prednisone) to an antiviral regimen may slightly reduce short-term pain, but their use remains controversial. In addition to possible serious side-effects associated with corticosteroids, these drugs are not effective for the prevention of post-herpetic neuralgia.

Many patients with zoster also use non-steroidal anti-inflammatory agents for pain management, and some with severe pain also require treatment with opioid narcotic agents.

There are several medications available for the management of post-herpetic neuralgia. The most commonly used agents include oral tricyclic antidepressants (such as nortriptyline), the oral anticonvulsant gabapentin, and topical lidocaine (anesthetic) patches. Topical capsaicin is also effective. A few patients require ongoing treatment with opioid (narcotic) agents for severe pain. Some early evidence suggests that injections of botulinum toxin may be helpful in patients suffering from severe post-herpetic neuralgia.

Can Zoster be Prevented?

The zoster vaccine, approved by the FDA in 2006, is indicated for the prevention of zoster in adults age 60 years and older. By boosting a person’s immunity to the zoster virus, it has been shown to reduce the likelihood of developing zoster (by 51%) and post-herpetic neuralgia (by 67%), as well as reduce the severity of pain in those vaccinated patients who still develop zoster. The zoster vaccine is not approved for patients with immune problems or on immune suppressing medications, or patients who are pregnant. Some argue that patients in their fifties should also receive the vaccine, but data on outcomes in this group are not yet available.

In the US, universal vaccination against chickenpox is now recommended for children (the chickenpox vaccine, approved by the FDA in 1995, is a different product than the zoster vaccine). This may have several unpredictable effects on the future epidemiology of zoster. It is not currently known how many of these vaccinated children will eventually develop zoster (though the incidence will likely be decreased). Also, periodic exposure to individuals with chickenpox is thought to provide a boost in other patients’ immunity to VZV, thus reducing their chances of developing zoster. Therefore, some have argued that the routine use of the childhood chickenpox vaccine might actually increase the incidence of zoster in older individuals who do not receive the zoster vaccine and are no longer receiving this “booster effect” from children infected with chickenpox.

(Nothing in this Knol should be construed as individual medical advice. Patients should consult with their own physician regarding the diagnosis and treatment of zoster and post-herpetic neuralgia. Not all of the medications discussed are FDA-approved for the treatment of zoster, and some side-effects and contraindications have not been listed.)