MIFFLINBURG, Pa. -- Bedtime comes early at the Martin farm, where life is still ordered by the rhythms of nature and the Old Order Mennonite faith. By dinnertime, with the cows milked and the animals fed, Amy, 10, and Derick, 12, are struggling to stay awake.
By 8 p.m., they are off to bed, soon fast asleep beneath rows of special 4-foot fluorescent lights that bathe them all night in a purplish-blue glow.
The lights keep them alive.
Amy and Derick have a rare liver disease that causes a dangerous accumulation of a substance called bilirubin. It yellows their skin and the whites of their eyes and could kill them if too much builds up.
Each night they must sleep under special lights to break down the bilirubin and clear it from their systems. Without the lights, they could suffer brain damage and die.
The disease, Crigler-Najjar syndrome, is extremely rare -- there are believed to be no more than 200 cases worldwide. But among the Mennonite and Amish communities, it's all too familiar. Three of Amy and Derick's cousins have it; so do 16 other Amish and Old Order Mennonite children in the area.
Crigler-Najjar is one of dozens of rare inherited disorders that run through the plain sects of Pennsylvania. A Lancaster doctor who cares for the families has counted 38 disorders in Amish children and 23 disorders among Mennonites that are found far less often in the general population.
Many of the disorders are metabolic, requiring special diets and medication. Others involve physical defects -- one is marked by dwarfism and extra fingers or toes; another produces babies with very small heads.
For the Martins, the deadly liver malady affecting two of their four children has meant learning about a disease almost no one has heard of -- and living every night with the lights.
"I don't like it because sometimes it's kind of hot," says Amy, whose panel of eight long bulbs hangs just above her when she is stretched out in bed. In winter she cannot wear a nightgown or use covers because the light must shine directly on her skin.
Derick keeps a flyswatter next to his bed because of the insects drawn to the lights.
"They buzz and hop around," he says. "If I get them, I make sure they're dead."
Often, Amy and Derick are awake before dawn, unable to sleep because of the lights.
"Amy didn't sleep through the night until she was 7," says Katie Martin, their mother.
It's a strange nocturnal routine. But Katie and her husband, Floyd, have known nothing else since the yellow tinge of Derick's skin at birth turned out to be far more serious than temporary newborn jaundice.
"Sometimes people ask if I just see yellow, because my eyes are yellow," says Amy.
At the clinic
There's a small wooden sign by the lane to the Clinic for Special Children, two miles from picturesque Strasburg, Lancaster County. It's easy to miss driving by, past Amish farms with dark-colored clothes drying on lines and tobacco leaves hanging in the barns.
The clinic, a handsome building with cedar siding and a slate roof, sits on an Amish farm. It has a hitching post in the parking lot.
In this unlikely setting for cutting-edge medical research, Dr. D. Holmes Morton, 52, and his staff are treating and studying the unusual genetic diseases that turn up among the insular communities of the plain sects.
Most of the disorders follow a recessive pattern of inheritance, passed on by two parents who carry a genetic mutation and are themselves unaffected, but whose babies have a 1-in-4 chance of having the disease.
The Amish and Mennonites both sprang from Swiss-German Anabaptists who began migrating to Pennsylvania in the 1700s. Since most of the 20,000 modern-day Amish in Lancaster County are descended from a few dozen settlers, the resulting gene pool is not as diverse as the general population. The sects are relatively closed societies whose members tend to marry within the group, increasing the chances that two people with the same gene mutation for a certain disorder will get together and pass it along.
At the same time, certain genetic diseases relatively common in the general population, such as cystic fibrosis, are unknown among the plain sects.
Miriam Martin carried a plate of peanut butter cookies when she, her sister-in-law Katie Martin and their children piled out of a van in front of the clinic.
Twice a year, they bring their five children with Crigler-Najjar to the doctor, hiring a driver to take them.
The Mennonite families avoid modern conveniences such as TV and radio, and close to home they travel by buggy. Miriam and Katie's families moved from Lancaster County to rural Union County in the late 1960s.
"We think the world of Dr. Morton," says Katie Martin. "If it wasn't for his help, we wouldn't be here."