Herpes zoster, also called shingles, is caused by the same virus (varicella-zoster, or VZV) that causes varicella (chickenpox); the virus lies dormant in the dorsal root ganglia for many years until reactivated by an unknown mechanism. The rash appears on one side of the body and rapidly evolves into blisters that cause severe pain.
Description
It is estimated that 1 million cases of shingles occur in the U.S. every year. Herpes zoster can occur at any age, but approximately half the cases are in individuals 60 years of age or older. Since 90 percent of adults have had chickenpox, all of these individuals are at risk for developing shingles.
Severe burning pain on the affected side usually precedes the rash by one to three days. Movement may aggravate the pain.
The duration of the disease is seven to 10 days. However, it may take up to 30 days for the shingles rash to resolve. Patients with herpes zoster can transmit the infection to individuals who have never had chickenpox (seronegative).
When branches of the trigeminal nerve (especially the ophthalmic branch) are involved in shingles, lesions on the face, mouth, tongue and eye could occur. The latter is referred to as ophthalmic zoster and may lead to blindness.
Treatment
Effective oral antiviral therapy is acyclovir (800 mg five times daily for seven to 10 days), or more reliably and conveniently, either valacyclovir (1 g three times daily for five to seven days) or famciclovir (500 mg three times daily for seven days), which result in accelerated lesion healing and decreased pain.
Early therapy with a glucocorticoid (prednisone 60 mg per day tapered over three weeks) in combination with antiviral therapy can significantly decrease postherpetic neuralgia (PHN), defined as pain persisting for more than 30 days after skin lesion resolution; however, steroids do not decrease pain duration or produce a more rapid resolution of the rash.
Immunocompromised patients with shingles should be treated with intravenous acyclovir to avoid dissemination.
Prevention
Zostavax (Zoster Vaccine Live) has been approved by the U.S. Federal Drug Administration for prevention of herpes zoster in individuals 60 years of age or older. It is not indicated for the treatment of shingles or PHN.
Complications
PHN, or long-term nerve pain, is the most common complication of shingles; it can last from months to years and is difficult to treat. The following drugs are used to treat PHN: amitriptyline, doxepin and gabapentin. While rare in young patients, 50 percent or more of patients older than 50 years of age experience PHN, which can be moderate to severe and cause skin tenderness with burning, shooting or stabbing pain.
Prognosis
Most people recover from shingles completely. An elderly or debilitated patient may have a more protracted course. Also, an immunocompromised patient usually has a more severe and prolonged course that can last weeks or months. Shingles recurs in 2 percent of normal, healthy people but in up to 20 percent of AIDS patients.
References
- "Harrison's Principles of Internal Medicine, 16th Edition"; R.J. Whitley; 2005
- "Office Textbook of Medicine, Fourth Edition"; William T. Branch; 2003
- Merck.com: Zostavax
