- The Washington Times - Tuesday, November 12, 2002

To say that Katie Mahar is sensitive to the sun is an understatement. Unlike most individuals who get sunburned and recover, Katie, 10, of Craryville, N.Y., cannot tolerate any ultraviolet light. Her home, car and school classroom all have tinted windows. Whenever she ventures outdoors during the day, she covers herself from head to toe in sunscreen, sunglasses, multiple layers of clothes and blankets. This is because her body lacks the proteins necessary to repair her DNA after exposure to the sun. If she is in the presence of sunlight, it inevitably causes damage to her cells and leads to cancers on her skin and eyes.
"I get little red dots where I get sunburned," she says. "Then, they bubble up to big blisters. It's cool to go out at night. There are lights on my house that shine down. That's what helps me see in the dark."
About 200 people in the United States, or two to four persons in about 1 million live births, suffer from xeroderma pigmentosum, a rare genetic defect that causes extreme sensitivity to the sun's ultraviolet rays. Ultraviolet light disrupts normal cell functioning in people who have the disorder, causing cancerous cell changes. It is so uncommon that no one in the Washington, D.C., area is known to have the disease, but many professionals in the region study the condition to learn more about it and other skin cancers.
Although there are various degrees of the disorder, most persons with xeroderma pigmentosum acquire an unusually severe sunburn after any sun exposure, although using sunscreen and layering clothes sometimes protects against the sun's negative effects. Dr. Kenneth H. Kraemer, research dermatologist at the National Cancer Institute in Bethesda, says patients with the disease have a thousandfold increase in their chances of getting skin cancer compared to the average person. The first skin cancer may develop before a person is 10 years old, and many other skin cancers may occur in the future.
"If people have it, they can live with it, but it changes their lifestyle tremendously," Dr. Kraemer says. "When we first started working on this in 1971, sunblock didn't exist. At least now you can go to the drug store and find all kinds of SPFs."
Activities that most people would consider ordinary, such as grocery shopping or eating at a restaurant, can be complicated for people with xeroderma pigmentosum, says Caren Mahar, Katie's mother. No one else in the Mahar family, past or present, including Katie's three siblings, has the disease. Mrs. Mahar has adapted her life to take special precautions for Katie she knows that the more she shelters her daughter from the sun, the longer Katie will live. Life expectancy for people with the condition is about 20 years, but it varies from person to person.
Along with tinted windows in their home, Mrs. Mahar never opens the windows or mini-blinds. For fresh air, she runs the air conditioner year-round. She locks all the doors in the house as soon as entering so no one accidentally lets in light. Further, none of the artificial lights in the home can be fluorescent, which is a form of ultraviolet light. When visiting any other location, Mrs. Mahar calls ahead to inquire about the type of lighting present. Katie attends fifth grade at Taconic Hills K-12 School in Craryville, N.Y, a learning institution that accommodates her needs.
"Whenever someone new comes to our house, even though they think they know about xeroderma pigmentosum, they really don't," Mrs. Mahar says. "We live in almost a cave-like environment."
To compensate for opportunities that Katie misses, Mrs. Mahar organizes special events, such as sleepovers with Katie's friends every weekend. Mrs. Mahar also started the Xeroderma Pigmentosum Society (www.xps.org), a nonprofit organization that sponsors Camp Sundown, a nighttime camp held in the summer that is open to xeroderma pigmentosum patients and their families. Sufferers of other light-sensitive conditions also are welcome. This summer's camp was free to patients and one accompanying adult if the patient was younger than 16.
"It offers the maximum amount of time to just be kids," Mrs. Mahar says. "As Katie gets older and she becomes aware of the world around her I hope she doesn't become a rebellious teenager."
Bill Jeffries, 57, of Ridgeland, S.C., who suffers from xeroderma pigmentosum, says when he was growing up his parents lacked the resources available today. He is a patient of Dr. Kraemer's and visits the National Cancer Institute for exams about every three months.
"When I was a young teenager, there were very few people who were known to have this disease," he says. "There were no sunscreens. There was no literature to go by. I was one of the youngest at the time to have it. We just played it by ear."
Since Mr. Jeffries has a milder form of the disorder, he has had a longer life span than most people with the condition. He still applies sunscreen when he leaves the house, however, and tries to limit his time in the sun. He has about 25 tumors removed from his skin each year.
For about 40 years, he worked as a craftsman who installed floor coverings with the help of his wife, Alice, but now he receives disability income. The couple had two children, who are free of xeroderma pigmentosum.
"I'm sure I probably go out more than I should, but I have a philosophy about things," he says. "I can't stay locked up in my house like a slave or a prisoner. I'd rather not be living. I go to church. I go to functions they have. I do anything you would do."
Learning about xeroderma pigmentosum also allows researchers to understand the importance of healthy individuals protecting against sun exposure, says James Cleaver, director of the skin cancer program and professor of dermatology at the University of California San Francisco. Although sunlight is the major environmental factor that triggers xeroderma pigmentosum, sunlight also causes many other skin cancers that develop in the same way, but at a slower pace. Healthy individuals have the proteins needed for DNA repair for about 60 years, but if that system fails, skin cancer occurs.
"Skin cancer is the most common human cancer," he says. "It's almost entirely preventable in the normal part of the population."
Researchers continue to search for ways to treat xeroderma pigmentosum patients, as well as help people with other forms of skin cancer, says Daniel B. Yarosh, president of Applied Genetics Inc., in Freeport, N.Y. He is developing a cream, called T4N5 liposome lotion, to aid xeroderma pigmentosum patients in DNA repair. The cream has been through one round of clinical testing in a lengthy process and is under review by the Food and Drug Administration in Rockville.
"When it's approved, it would be part of potential treatment, since there is so little that can be done for these patients other than keep them out of the sun and monitoring them for skin cancers," he says.
Mr. Yarosh says the liposome lotion should be applied after sun exposure to deliver an enzyme needed to repair DNA after experiencing ultraviolet light. The enzyme is encapsulated in liposome, a microscopic sphere made from fat molecules. When tested on a group of patients with xeroderma pigmentosum, the patients who used the cream had 30 percent fewer new cancers than those who did not use the cream.
In the past, Accutane, a drug used to treat severe acne, has been effective in suppressing skin cancers, but it has multiple side effects, including depression, Mr. Yarosh says. When Accutane use is discontinued, the cancers usually return.
Aside from treating the disease, medical professionals also are becoming better equipped to diagnosis it. Dr. William Fishbein, chief of the biochemical pathology division in the department of environmental and toxicological pathology at the Armed Forces Institute of Pathology in Northwest, runs screening tests for people believed to have xeroderma pigmentosum. Sometimes, people who thought they had the disorder actually have other light-sensitive diseases.
Dr. Fishbein takes biopsies of cells from patients and studies them under ultraviolet light to see whether the cells die at a normal or increased rate. If they die at an increased rate, he performs two more tests to distinguish which light sensitive disease the patient has.
"It happens to be a very complex area, and it's still unfolding," Dr. Fishbein says. "The way it works is being learned more and more and more."

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