(Owen Freeman/For The Washington Post)

Dorsey Davidge felt her thrumming anxiety burst into barely controlled panic as she watched her 14-year-old daughter Cate Chapin struggle to get from her bedroom to the bathroom.

During the last week of January, the eighth-grader contracted what appeared to be a bad case of the flu. After a week, a doctor decided she had pneumonia, a diagnosis that was later changed to a possible infectious disease. Davidge, a single mother who lives in McLean, had maintained her equanimity during the early days of Cate’s illness. But when she saw that her older daughter was unable to walk 10 feet without stopping midway to rest, she was shocked by how cadaverous-looking Cate had become in a matter of weeks.

“I was really scared for the first time,” Davidge said. “She was in­cred­ibly weak, and I thought, “ ‘Oh, my God, my child is just wasting away.’ ”

By then, the 5-foot-2 Cate, a skinny 95 pounds before she got sick, had shriveled to a little over 80 pounds. She had no appetite, was barely drinking anything and seemed unable to consume more than a quarter of a bagel at a sitting.

“That day was the last straw,” Davidge recalled. She telephoned Cate’s pediatrician, who agreed that the girl needed to be admitted immediately to a Northern Virginia hospital.

Now that Cate Chapin’s illness has been properly diagnosed, the teenager has regained much of the weight she had lost. (Family photo)

It would take another harrowing month — which included the insertion of a feeding tube to help restore Cate’s weight, consultations with a bevy of specialists and numerous tests — before doctors figured out what was actually wrong, a diagnosis made possible after Cate developed a seemingly unrelated condition that sent her to an ophthalmologist.

“I was so excited when I saw her for the first time, because I thought, ‘This puts [her illness] in a whole new category,’ ” said Melanie Buttross. Like some of the other specialists treating Cate, Buttross initially thought her illness was the result of a smoldering infection.

But that theory was quickly upended by what Buttross saw when she examined Cate’s eyes.

Flu aftermath

Cate’s January illness bore the hallmarks of the flu: Lethargic, achy and feverish, she had missed a week of school and showed no sign of improvement when her mother took her to the pediatrician. The doctor agreed she had some sort of virus and would probably feel better soon.

But five days later, Cate was no better. During a second visit, the pediatrician decided she probably had pneumonia. “She’ll be able to go to school in a few days,” Davidge recalls the doctor telling her as she prescribed antibiotics to knock out the lung infection.

The antibiotics didn’t help, and two days later, Davidge took Cate to a nearby emergency room. While undergoing a chest X-ray to confirm the pneumonia diagnosis, Cate fainted. The probable cause was dehydration; doctors gave her an intravenous drip to rehydrate her and anti-nausea medications.

The following week, she was back in the pediatrician’s office. The chest X-ray had found nothing. Nor did subsequent blood tests reveal a reason for Cate’s worsening weakness and dramatic weight loss.

Unhappy because her pediatrician seemed unresponsive, Davidge switched practices. The new pediatrician thought Cate might have an infectious disease. She referred Cate to a pediatric infectious-disease specialist, who suspected mycoplasma.

Once dubbed “walking pneumonia” because people walked around with the infection without seeming very ill, mycoplasma is typically a mild infection that may not require treatment. It often develops after a respiratory problem such as the flu, lasts a few weeks and most often causes a persistent dry cough, sore throat and weakness. But Cate was much sicker than most young mycoplasma patients. Her rapid and increasingly noticeable weight loss, coupled with her pronounced weakness and nonexistent appetite, suggested another cause: anorexia.

Davidge said she told doctors who raised that possibility that she was skeptical. “She had never had an issue with food or eating,” her mother said.

The day she struggled to walk down the hall, Cate was admitted to a Northern Virginia hospital. There, a team of specialists, which included a gastroenterologist, a psychiatrist and a pediatrician, labored to figure out what was wrong. She underwent an endoscopy and colonoscopy and an extensive gastrointestinal workup, which uncovered nothing. A kidney specialist was called in after it was determined that her kidney function seemed impaired. Signs pointed to a possible diagnosis of Fanconi syndrome, in which protein and other substances that should be absorbed by the bloodstream are released into the urine. And she seemed to have a form of nephritis, in which the spaces between the kidneys become inflamed.

But Davidge said that doctors kept also circling back to anorexia. Self-starvation can wreak havoc with kidney function and would account for her weakness.

There was an another factor that colored Cate’s hospitalization: She was often angry and uncooperative and at times actively resisted treatment; getting her to drink the prep needed for a colonoscopy took hours, her mother recalled. The psychiatrist treating her told Davidge that he was “having trouble getting a read on her” since she wouldn’t talk to him.

When Cate’s weight slid to 80 pounds, doctors recommended the insertion of a nasogastric feeding tube, which enabled her to receive a steady infusion of calories. Davidge agreed to the procedure. On Feb. 28, after a week in the hospital, Cate was sent home.

“They said there really was nothing else to do and that hopefully with the feeding tube she would gain weight,” Davidge recalled. A home health nurse visited every few days and Cate saw her pediatrician several times a week.

She began gaining pounds, but after a few weeks her weight plateaued. Her kidney function remained abnormal and the nephrologist suggested that she might have to undergo a kidney biopsy to try to see what might be wrong. During the previous month, doctors had ruled out juvenile rheumatoid arthritis, lupus, mononucleosis, cancer and Lyme disease.

“It was a very, very emotional time," her mother said. “We were just sort of muddling along."

A revealing new symptom

Three weeks after she was discharged, Cate was resting at home when she suddenly developed an intense sharp pain in her left eye, which was also badly inflamed. Davidge wondered if she might have conjunctivitis, a contagious inflammation of the white of the eye, commonly known as pinkeye, or something more serious. Davidge called Buttross, her ophthalmologist and a friend, and sent her a cellphone photo of Cate’s eye.

Buttross, concerned that the orbit, or eye socket, might be infected and aware of Cate’s recent hospitalization, told Davidge to take her to the emergency room. A CT scan showed no infection; Cate was sent home with a diagnosis of conjunctivitis.

The following day, because her eye was still acutely painful — and conjunctivitis rarely is — Davidge took Cate to see Buttross.

While examining her eyes, the ophthalmologist said she realized the problem was neither pinkeye nor another infection.

“I saw white blood cells — inflammatory cells — circulating” in the front of her eye, Buttross recalled. They resembled tiny dust particles floating in a sunlit room. Although the cells were present in both eyes, Cate’s left eye looked especially affected, Buttross said.

“I knew this was uveitis,” she said. An inflammation of the middle layer of the eye, which provides blood flow to the retina, uveitis can be caused by injury or an autoimmune reaction, in which the body mistakenly attacks its own tissue. If not treated promptly, uveitis can cause permanent vision loss.

Buttross suspected that the eye disorder might provide a clue to Cate’s recent medical problems, but she wasn’t sure how. And because she is not a uveitis specialist, she referred Cate to an ophthalmologist who is.

A few days later, the answer was revealed. Based in part on Cate’s recent history, particularly her malfunctioning kidneys, the uveitis expert determined that she had an extremely rare disorder known as tubulointerstitial nephritis and uveitis syndrome, also known as TINU.

The poorly understood disorder, first described in 1975, typically affects adolescent girls and may be the result of an autoimmune malfunction. In some cases it is preceded by an infection. Cate’s mycoplasma infection might have triggered it, although there is no way to know for certain. Other reported causes include the use of the Chinese herb goreisan, which Cate had not taken.

The hallmark symptoms of TINU are uveitis and interstitial nephritis. Sometimes the kidney malfunction precedes the uveitis; in other cases, uveitis occurs first. Other symptoms of TINU include weight loss and weakness. Treatment typically involves steroids. To date, only 200 cases have been reported in the medical literature worldwide, and many doctors are unaware of its existence.

“It’s really an obscure disease,” Buttross said. “I had never heard of it, although I’d love to say I had.”

For Davidge, the diagnosis was an enormous relief. “Finally we knew what we were dealing with,” she said.

Cate had started using steroid eye drops that Buttross had prescribed at the first visit; within a few weeks, she felt better and gained weight more rapidly. On April 2, when she hit 92 pounds, the feeding tube was removed. Her kidney function continued to improve.

Because the disease is so rare, Cate was referred to the National Eye Institute. With the help of an at-home tutor, she managed to complete eighth grade and is now thriving as a high school freshman at a private school, although she still tires easily. Her kidneys are again functioning normally.

She sees Buttross regularly and last month began receiving injections of methotrexate, a drug used to treat certain cancers, because steroids alone have not cleared the uveitis. She is being weaned off the steroid eye drops.

“Although people talk about a cure, it’s really about living with a chronic condition that can be managed,” Davidge said. “I’d say she’s at 90 percent.”

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