From PEOPLE Magazine Click to enlarge
It is 8 o'clock, the sun has just gone down in Meridian, a tiny farming community 120 miles north of San Francisco, and 5-year-old Jaime Harrison and her sister, Sherry, 3, are going out to play in the gathering darkness. With their parents, Kim and Jim, trailing behind, the pigtailed girls hop on pink and purple bicycles and, shrieking with delight, begin their regular twilight ride to the deserted center of town, where they can gambol in safety.

The first stop is the darkened Meridian post office, where the youngsters exuberantly open and shut the outdoor mailbox, pretending to send letters. Soon their 12-year-old half-brother, Bobby, cruises by on his skateboard to see what his sisters are up to this night. Then it's on to the Meridian Meat Market and the gleaming lure of the Coke machine that stands outside. There is a hazard here, and the parents become edgily watchful; the girls must not scamper off to the corner, where there is a stand of street lamps whose bright white light could fall upon them.

Often, on warm nights like this, the Harrisons picnic in Maple Park, shielded from the yellow glare of street lamps by the enshrouding trees. There, with a kerosene lantern casting a soft, golden glow, Kim sets out a fast-food feast of burgers, fries and sodas. After dinner, the children's laughter echoes in the stillness that envelops the park playground, where they have the swing and slides and the cool, dark sand all to themselves. An hour later, their nightly playtime over, the ebullient family heads for home.

The Harrison girls are very accustomed to the dark. It has been more than three years since Kim last saw Jaime frolic in the daylight—Sherry has never been in direct sun—and she keeps a sharp mental picture of that moment: Jaime, 18 months, "was chasing some butterflies up a grassy hill," Kim recalls. "She was wearing blue pants and a rust, white and blue shirt." Kim cherishes that image because, although no harm came from it, she will never enjoy such an outing with her girls again. Soon after that sunlit butterfly chase, Jaime and then Sherry were diagnosed with xeroderma pigmentosum, or XP, a rare, often fatal genetic disorder that leaves its victims acutely vulnerable to skin and eye cancers if they are even briefly exposed to sun or any ultraviolet rays. The news almost made Kim and Jim give up hope of a decent life, for themselves or their children, but they passed through that time. And since then, under their parents' ceaselessly vigilant care, Jaime and Sherry Harrison have spent their lives romping in darkness.

The critical faculty that Jaime and Sherry lack is an essential health-sustaining system. "As it does in all people, sunlight damages a cell's DNA, its genetic material," explains Dr. Kenneth Kraemer, a dermatologist and research scientist at the National Cancer Institute in Bethesda, Md. "Unlike most people, XP patients lack a system to repair the damage." The normal repair system consists of enzymes that first excise the damaged DNA in cells, then fill in the gap with undamaged DNA. Xeroderma pigmentosum, a Latin phrase meaning pigmented dry skin, is a calamity that can result when two people who happen to carry the rare, recessive gene have children. When Kim and Jim fell in love and married in 1984, neither had any idea that they both carried a gene that appears in only one in 200,000 people in the U.S.; even then, their chances of having an XP child were no more than one in four. Scientists think that finding the defective enzyme in this tiny group of XP sufferers may ultimately lead to a greater understanding of how all skin cancers occur and what role the environment may play. Consequently, although there are fewer than 1,000 XP victims in the U.S., researchers around the world are hunting for a cure for this obscure genetic disease.

Until those efforts pay off, Kim and Jim Harrison are relying on their own preventive measures. "If a kid is allergic to bee bites, you keep him away from bees," says Jim, 34, and he and Kim, 30, who are emotional and determined people, have changed their entire way of life and go to extraordinary lengths to safeguard their daughters. Kim is by their side day and night, and Jim's only evenings off are spent with Bobby. When the girls must go out in daylight to see a doctor, they are slathered with No. 50 sun block, swathed in turtlenecks, tights and hats, shielded behind ultraviolet-proof glasses and carried to the family van, which has protective film on all its windows. In their large, rambling home, shadows predominate. Curtains are drawn tight over all windows. When an outside door needs to be opened, Kim shoos the girls into another room, and she's always on guard in case one of them gives way to temptation and peeks out under a curtain. Low-watt light bulbs are used sparingly. Otherwise the house is illuminated by candles.

Yet it is a joyful house. The children brim with laughter and mischief—their only observable impairment is a slurring of speech, which may be a physiological effect of the disease. Kim, who once worked as a preschool aide and ran a day-care center in her home when they lived in Illinois, has begged or borrowed a slew of toys from local service clubs, preschools and individuals. "There's not a room in this house that they don't have something to play with," she boasts. In a playroom Mickey Mouse curtains cheerfully block out the enemy sun. A big rubber bouncer with colored climbing poles sits in one corner, a gym and slide in another, and the girls regularly bounce, slide and whoop there. Outside the real kitchen is a play one with toy dishwasher, stove, microwave and sink. Neighbor kids often stop by to join in games with Jaime and Sherry. Three small puppies have just joined the murkily lit household.

So far, the girls have also been kept in the dark about what is wrong with them. "I won't lie to them," says Kim, "but I can't see dumping the whole thing on them at 3 and 5 years old." But it's getting harder to dodge the truth. "When Jaime was 2, she tried to sneak outside," recalls Kim. "I told her she couldn't go out in the sun because it would hurt her, and that was enough." Now Jaime is asking more pointed questions. Recently, she wanted to know how come other kids could go outdoors without sunglasses and why it's okay for boys like Bobby, but not girls. "I told her some people can go outside and some can't, and that it doesn't matter if you're a boy or girl, or big or small," says Kim. "That's what I've gotten away with so far.

"We work at keeping them happy, well-adjusted and stimulated, but sometimes we get real stale," she adds. "They get tired of me, and I get tired of them."

And sometimes, like all siblings, they get tired of each other. Despite a fondness for dressing in identical Mickey Mouse outfits sent by Jim's mother, the girls are temperamental opposites. "Jaime is very cooperative—she's peaceful, delicate and well-behaved," says Kim. "Sherry, on the other hand, doesn't do anything you say. Jaime goes around cleaning up the house, and Sherry goes around tearing it up. They are," she says with unconscious irony, "like night and day." Nonetheless, the sisters are nearly inseparable. "There are times I am so happy Jaime is not alone in this," says Kim. "I would not give Sherry XP on purpose for anything, but since it happened, there is a good side to it."

It took some time for the Harrisons to see any positive aspects at all in their daughters' affliction. "When Jaime and Sherry were first diagnosed, we were ready to go right off the bridge and say the hell with going home," Jim admits. The first troubling signs came when Jaime was 2 months old and on a family vacation in Montana. "She hated to go outside. She would scream and thrash and fight," says Kim. "We loved the outdoors, but in her baby pictures she is always closing her eyes real tight." During the vacation, Jaime developed burns and blisters. Doctors diagnosed them as a rash and gave her cortisone, then changed the diagnosis to impetigo, then allergies. Because the symptoms didn't appear for one or two days after her exposure to sun, says Kim, "We had no idea it related to being outside. The doctors didn't either."

At that time, Kim and Jim had been married for a year and were living in Aurora, Illinois; when they wed she was a single mother attending community college, and he had just been discharged from the Air Force. During the frigid Illinois fall and winter following their Montana vacation, their baby was kept indoors or bundled up. But in the spring, when the family began going to Bobby's Little League games and to neighborhood cookouts, the symptoms came back. One day, while the Harrisons were driving home from three days of camping in Wisconsin, Jaime's face grew red. That night she woke up covered with terrible blisters, running a 105-degree fever. She could not even cry, because the skin around her mouth cracked and bled when she grimaced. Kim and Jim rushed the child to the emergency room, but the doctors couldn't pinpoint what was wrong. The Harrisons were referred to Dr. Nancy Esterly, a dermatologist then at Chicago's Children's Memorial Hospital, who put Jaime through a battery of tests.

Just before Thanksgiving 1986, a skin biopsy revealed the truth. The Harrisons were told that Jaime, like most XP victims, would eventually die of melanoma cancer at a young age.

"With genetic defects, you start out blaming yourself, then your parents," says Kim of that devastating time. "The worst thing was trying to find help. There were no support groups, no other families to talk to to find out how to deal with this. I was so scared. I just closed the house up tight as a drum. At night I'd take Jaime out of her bed and put her into my bed and hold her all night. Night after night I did that. We lived like there was no tomorrow. If Jaime wanted to eat a box of candy for breakfast, that was fine. She could watch TV anytime. She could do anything she wanted with the time she had left." Only concern for Bobby and Sherry kept the Harrisons going at all.

At the same time, Kim and Jim dreaded the prospect of testing Sherry, then 3 months old and apparently symptom-free, but finally they gave in to pressure from their doctors. Ten weeks after Jaime had been diagnosed, the results on Sherry came back positive, and their whole world seemed to crash to an end.

And then one day, three years ago, they began to fight back. "I said to myself, 'I've got to start living,' " Kim says. " 'I love them too much to say goodbye. Instead of lying in bed and crying at night holding on to the kids, I have to fight this disease.' "

"We had kids because we wanted them," Jim says now. "And we want to make sure they get a full life before their time comes."

Kim started planning their days, scheduling time for coloring, then finger painting, toe painting, block building. Soon the girls were playing soccer in the living room and dancing with awkward enthusiasm to Disney tapes. Kim read every clinical paper on XP she could lay her hands on. "I dissected words for hours to try and figure out what the heck they meant," she says. In her reading, she found the name of James Cleaver, a professor of radiology at the University of California, San Francisco, who in 1968 had been the first in the world to identify the DNA defect that causes XP. The Harrisons decided to move to California so that he could advise them. Only later did they learn that Cleaver had been sent the girls' test results by their doctors in Chicago and had confirmed the diagnosis.

The Harrisons sold off most of their furniture to raise cash for the trip and in February 1987 headed west in a Jeep, towing an engineless van stuffed to the roof with toys. They arrived jobless and broke. A sympathetic building manager rented them an apartment and let them pay for it a little at a time, until Jim landed a cabinetmaking job. Then they went to see Cleaver.

"Poor Dr. Cleaver," says Kim. "We never told him we were coming. We just walked in and said, 'Here are our kids—help.' "

While Cleaver could offer no cure, he could help the Harrisons better understand what they were up against, and he put them in touch with other XP families. "He gave us options, ideas and encouragement," says Jim. "And he gave us hope." He also endorsed their radical approach to protection. "If their children have very few symptoms," Cleaver says, "it will give us an indication that we can improve the life of XP patients." Kim and Jim have no doubt at all they are doing the right thing. "What the doctors told us to expect has not happened," says Jim. "Jaime and Sherry are cancer-free. Obviously we're doing something that is making a big difference."

The future is still awesomely uncertain. The impairment of the girls' speech could indicate progressive neurological damage: such degeneration, observed in 20 percent of XP victims, could lead to hearing loss or mental impairment. A speech therapist works with Jaime once a week, and doctors feel that she's too young to go through the long testing needed for a definitive neurological diagnosis. The Harrisons have worked out an agreement for a kindergarten class to be held in their house one day a week next year but worry that other kids will make fun of Jaime. And all the attention to the girls has been tough on Bobby. "If my friends want me to go to a party during the day, my mom can't take me because of my sisters," he says resignedly. "They're normal sisters, all right, and they tease me and bug me." But he is very kind with them. "It's like they've been grounded for their whole life, and they don't deserve it," Bobby says, and he dreams of winning the lottery so he can pay people to find them a cure. Kim worries about Bobby, the more so because she and Jim won't risk having more children. "I have one healthy child, and I don't want anything to happen to him," she says. "I just want to take him and put him into my pocket, but I can't do that."

Nor can she keep their disease from the girls forever. Recently, Jaime has greatly stepped up her pressure to be allowed to escape into the outdoors.

"It's dark, it's dark!" she shouted one sun-drenched afternoon.

"No, it isn't dark." Kim replied. "Honey, I want to go out and play, too, but we can't yet."

"You're mean!" Jaime yelled.

And Sherry is getting even more rambunctious. One recent day she suddenly streaked for the front door, announcing, "I'm big now!" Kim nabbed her in the nick of time. One evening, shortly before dark, she bolted into the yard and had to be caught by Jim.

The genetic curse that blights the lives of their little girls "still makes us angry," says Jim. Kim has stopped looking for reasons. "We have tried to be good people," she says. "Things like this aren't supposed to happen to you." Both parents find their greatest source of support in one another. "We're good friends, and we're close," says Kim. "We cry sometimes. But then one of the kids will do something silly, or give you a hug, or tell you they love you. It reminds you that everything has been worth it."

And there is one more big factor. "Jaime and Sherry," adds their mom, "were born to have fun."

—Bonnie Johnson, Giovanna Breu in Meridian