(CNN) -- The day was supposed to be remembered as one filled with happiness. Their daughter, after all, had just turned 2 years old. Instead, Nikki Peterson remembers December 30, 2007 as the day her husband Billy got sick.
Billy Anderson's undiagnosed condition has kept him in the hospital for more than a year.
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Billy Anderson was in fine health until that evening last winter. He woke up in pain and his wife rushed him to the emergency room. Over the next few days, he suffered a number of ailments, from a running fever and hives to swelling joints.
Nikki says she knew there was something wrong when Billy, age 29, was no longer able to walk around the house. "This is a 6-foot, 240-pound guy who doesn't usually complain about anything," she says.
The couple, from Baxter Springs, Kansas, made three trips to the emergency room. On their third visit, Nikki refused to go home until doctors agreed to keep Billy in the hospital for further evaluation.
Since then, Billy has been in and out of intensive care. He's spent time on a ventilator and suffered kidney failure. His body isn't absorbing nutrients, and as a result, his 240-pound frame has been whittled down by 100 pounds. See photos of Billy and his family »
One year and a battery of tests later, doctors still haven't pinpointed the cause of his condition. At one point, they thought he had Crohn's disease, an inflammatory bowel disease, but that turned out not to be the case.
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They hope their story will reach someone who can help solve Billy's unexplained illness. Doctors have gone through at least 40 possible diagnoses, according to Nikki.
"We've been told that this is 'Billy's Disease,' and that this will be written about in medical journals. We hope somebody has missed a test or overlooked something," she says.
Billy, a father of two who dreams of opening up his own restaurant one day, appears to have some type of problem with B-cells that isn't genetic, according to Nikki. B-cells play a critical role in keeping the immune system healthy.
The ordeal has taken an emotional toll on the family. "It's been devastating. It's traumatic for the children to have to watch someone who was once so strong suffer," says Nikki.
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Being uninsured has added financial stress. Billy had just started a new job training to be a kitchen manager when he first got sick. As a result, he didn't have insurance. He was able to apply for Medicaid, but his coverage was canceled once he started receiving disability assistance.
He's cycled through five hospitals in the span of 12 months. Oklahoma University Medical Center, where Billy has been since mid-August, has become the family's second home. Nikki has moved to nearby Tulsa in order to be able to spend half of the week by Billy's side.
They hope their next move will take them East. Billy recently applied for the Undiagnosed Diseases Program at the National Institutes of Health. If he is accepted, he will be transferred to Bethesda, Maryland.
Nikki, who has started a support group for Billy on Facebook and provides updates on his condition on his MySpace page, says she refuses to give up: "Billy deserves every opportunity to survive. He's a hard working man who took care of his family."