What is herpes zoster (shingles)|
Herpes zoster is caused by the same virus that causes chickenpox (varicella zoster). When a person becomes infected with varicella, the virus travels from the skin, up the sensory nerves and becomes dormant in a bundle of nerves call the sensory ganglia. The virus can then be activated later in life, and travel back down the sensory nerve that supplies a specific area of skin known as a dermatome. The presence of the virus in the nerve causes it to become inflamed and very painful. The condition caused by this secondary reactivation is called herpes zoster, or shingles.
Who is at risk?
All races and both sexes are affected equally. Any one who has been infected with varicella zoster can later develop shingles. Reactivation of the virus may be spontaneaous or follow a period when the patient's immune system is not funtioning as well as normal. This could be due to fatigue, or stress after an emotional or physical trauma; due to diseases that compromise the immune system such as AIDs, Hodgkins disease, diabetes, or due to drugs like corticosteroids or chemotherapy. These patients are known as immunocompromised. Overall, approximately 20% of people with previous varicella infection develop herpes zoster later in life.
People become more immunocompromised as they get older, therefore the risk of developing shingles increases with age. It is not commonly seen among children, though teenagers and young adults are at a greater risk if the initial varicella infection occurred before the age of 2 years.
Symptoms may begin with fever, a vague feeling of weakness and discomfort. Then the patient starts to feel numbness, tingling, burning, itching or pain in the dermatome (area of the skin, supplied by a nerve) affected. This is usually in the region of the chest or back, but the face, and occasionally arms and legs may also be involved. More than one dermatome can be involved, but this is unusual.
Eruption of the rash may occur at the same time as onset of pain, or follow a few days later. Pain may be continuous or come and go, and last from 1 to 5 weeks. About 5% of patients also experience muscle weakness in the affected area due to involvement of nerves leading to the muscles.
The rash starts as red patches that develop into clear, fluid filled vesicles. The vesicles become cloudy, dry, then crust over and scab after 1 to 2 weeks. The rash generally heals well, rarely leaving a scar.
The total duration of the disease depends on when the vesicles first appear - if within 24 hours, the duration will be short. It usually lasts from 7 to 10 days, but it can take up to 5 weeks for the skin to heal. It also usually lasts longer in adults than in children.
The immunocompetent host is the patient who is otherwise healthy, and whose immune system is not compromised by other factors. For these patients, complications are usually mild and relatively rare, but the risk is there all the same.
- Some people, particularly females, continue to feel pain for months or even years after the rash has healed. This is called post-herpatic neuralgia, and can be excruciating. Post-herpatic neuralgia is the most common complication in herpes zoster, occuring in about 10% of cases. However it is more common as age increases. Post-herpatic pain is seen in 45% of patients over 50, 6% in adults younger than 50, but almost never develops in children.
- Ramsay Hunt syndrome occurs when the virus reactivates in the geniculate ganglion, affecting the ear, the side of the tongue and the roof of the mouth, causing loss of taste and hearing.
- If the eye is affected (opthalmic zoster), the mucus membranes and cornea can become inflamed which is very painful. Scarring of the cornea may even cause loss of vision.
- Reoccurrence of shingles occurs