WASHINGTON, May 19 (Reuters) - Shingles tends to run in families, indicating these people may have an increased genetic susceptibility to the viral disease marked by a painful, blistering rash, researchers said on Monday.
The researchers looked at 1,027 people treated at a clinic in Houston between 1992 and 2005, half of whom had shingles and the other half had skin conditions other than shingles.
Those with shingles were about four times as likely as the others to have had a close family member with the disease. In all, 39.3 percent of the shingles patients had such a relative, compared to 10.5 percent of the other patients.
Shingles, also known as herpes zoster, is caused by the same varicella-zoster virus responsible for the common childhood illness chicken pox. After a person has had chicken pox, the virus stays dormant in the body, but years later can reactivate in spinal nerves and cause shingles.
Doctors have puzzled over why some people get it while others do not. These findings may provide some of the answer.
"Twenty percent of people eventually develop shingles and 80 percent will not, no matter how long they live," Dr. Stephen Tyring of the University of Texas Medical School at Houston, one of the researchers, said in a telephone interview.
"So what's different about those 20 percent? It seems that the familial predisposition, which must translate into a genetic susceptibility, is a significant factor," Tyring said.
The study appeared in the journal Archives of Dermatology four days after the U.S. Centers for Disease Control and Prevention recommended that people 60 and older get Merck & Co Inc's
vaccine Zostavax to protect against shingles.
The CDC urged these people to get a single dose of Zostavax, the only vaccine to prevent shingles, even if they had a prior bout of shingles. There is no cure for shingles.
Nearly a million shingles cases are diagnosed each year in the United States alone.
'FIRST IN LINE'
"Since we now have a vaccine to prevent shingles, we can urge those who have had blood relatives with shingles to be first in line to get vaccinated," Tyring said.
Shingles causes a burning, painful skin rash with blisters that can last up to five weeks and pain that can endure for months or years. Left untreated, shingles can cause irreversible nerve damage. The risk for getting shingle rises starting at around age 50, and is highest among the elderly.
Researchers have struggled to understand the cause of the reactivation of the virus, but believe it may be due to stress, an impaired immune system or the effects of aging.
"The genetic propensity in the broadest sense would make reactivation of the virus more likely. But it may also be a genetic propensity to have a lower threshold to stress if stress indeed is a trigger," Tyring said.
Editing by Julie Steenhuysen and Cynthia Osterman
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