(USMLE topics) Herpes zoster: Nerve pain and skin rash caused by varicella-zoster virus (VZV), the same herpesvirus that causes chickenpox.
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Shingles, also known as herpes zoster, is a common condition characterized by nerve damage and a painful skin rash. It is caused by varicella-zoster virus, the same virus that causes chickenpox. The first exposure to the virus, usually during childhood, leads to chickenpox. After the primary infection resolves, the virus moves to sensory ganglia of the spinal and cranial nerves, where it becomes inactive.
The body’s immunity against chickenpox suppresses viral replication, keeping it dormant for decades. Reactivation of the virus occurs when this immunity weakens and fails to contain the virus. This can happen as a result of aging, stress, or other diseases.
Instead of another case of chickenpox, the reactivated virus causes shingles. It multiplies and spreads along the path of the infected nerve, resulting in damage and pain. The location of pain depends on the nerve that is affected. Because each spinal nerve supplies a specific area of the body, called a dermatome, the patterns of pain follow the dermatome distribution. When a cranial nerve is infected, face pain results. As nerves come in pairs and usually only one is affected, the pain is typically limited to a small area on one side of the body.
Shingles develops in 3 phases. Patients typically experience pain as the first symptom. The pain can be described as a stabbing pain, or a burning, numbness or tingling sensation. The area is sensitive to touch. Depending on the location, the pain can sometimes be mistaken for a lung, heart, or kidney problem. Less common symptoms include fatigue, headache and fever.
A painful skin rash appears in phase 2, a few days after the pain. The rash starts as small red dots, which develop into fluid-filled blisters. As the blisters follow the nerve path, they form a stripe on one side of the body. The blisters eventually dry out and crust over.
The healing occurs in phase 3, which may take several weeks.
There's no cure for shingles, but it is usually self-limited and resolves on its own. However, possible complications can be severe. Some patients may continue to experience debilitating pain beyond rash healing, in a condition known as post-herpetic neuralgia, PHN. The chance of developing PHN increases with age. Shingles that occurs on the face, neck or scalp, may lead to vision loss, hearing loss, or other neurological problems. If blisters aren't properly treated, bacterial skin infections may develop.
Prompt treatment with antiviral medications can speed up healing and reduce risk of complications. Pain can be managed with pain relievers, cool bath or cool compresses. The affected area must be kept clean and covered.
Most people get shingles only once, but it is possible to get it more than once. Shingles can be effectively prevented with vaccines.
