Medical students commonly hear the phrase, "If you hear hoof beats, think horses, not zebras."

The adage reflects a core tenet of the art of medical diagnoses: It's more productive to first assume common diseases are the cause of most patients' symptoms, rather than exotic disorders.

That medical mindset was evident when Kaycee Antosiak, a vivacious

12-year-old Los Altos girl, sought treatment for her crippling pain after a dog bite. While the bite healed in six weeks, excruciating pain set in, leading the active girl to collapse after a dance class. She then began using crutches and finally a wheelchair. During that time, she visited dozens of medical experts, none of whom could determine the cause of her increasing infirmity.

Three months after the dog attack, she was referred to a Stanford University physician, Dr. Elliot Krane, who correctly diagnosed her as having arare genetically linked disease called complex regional pain syndrome. The condition causes excruciating chronic pain, long after the generally minor injury that triggered it healed.

"These patients think their foot is immersed in boiling water all of the time," said Krane, a pediatric anesthesiologist at Lucile Packard Children's Hospital, who last week at Stanford led the first conference worldwide to seek faster diagnoses and better treatment of the condition.

"It just ruins the lives of these kids. The typical kid is in a wheelchair," Krane said. Their limbs, he added, are often blue and cold to the touch from misfiring nerve cells.

Before Kaycee visited Krane, she said, some doctors had suggested the pain was in her head.

"I told my parents, 'I don't think I'm crazy. My ankle really hurts,'" Kaycee recalled. Her mother, Donna Antosiak, speaks with a tone of shock at the memory of that time.

"She was screaming, 'Mommy, mommy, it hurts, it hurts!'" said Antosiak. "I was going out of my mind."

With the extraordinary challenge of diagnosing these uncommon conditions, and medical training that encourages doctors to focus on familiar causes of disease, most patients with rare disorders run through a gauntlet of doctors before — for the lucky ones — they end up referred to the unique physician with the knowledge to correctly pinpoint their disorder.

"I can't think of a single patient I've seen within a month of their onset of symptoms," Krane said.

"Sometimes it's a year and they're unable to walk," he added. Krane recognized within minutes the disease Kaycee had when he first saw her in November 2005 and immediately started her on treatment.

Although one doctor told her she'd never walk again, today the 12-year-old is back in dance class and plans on attending several camps this summer, including ones for acting, speech, volleyball and Irish dance. Occasionally, she said, her ankle still aches and she's aware she's vulnerable for life from the condition, absent the development of a treatment that permanently ends the pain.

Kaycee and others with complex regional pain syndrome are among the ranks of the 30 million Americans with one of the nearly 7,000 known rare diseases, according to Dr. Steven Groft, director of the Office of Rare Diseases with the National Institutes of Health. The NIH defines a rare disease as one affecting 200,000 or fewer Americans.

They carry strange names like Madelung's Disease, which causes abnormal fat accumulation around the neck and shoulders; Kufs Disease, a neurological disorder that mimics a mental illness; or the horrific fibrodysplasia ossificans progressive, which causes muscle tissue and ligaments to turn to bone, encasing the person in bone.

The prevalence of those living with these unusual conditions numerically rivals the 40 million Americans with one or more of the three major diseases: heart disease, cancer or diabetes.

The number of patients identified with a rare disease also is expected to swell with expanding knowledge of the human genome, said Groft. Rare diseases are usually attributed to genetics. In fewer cases, they're caused by infectious agents like viruses or bacteria.

"What we're finding is that as more information becomes available, there are more and more patients who have the rare disorder," Groft said. "With the arrival of the Internet, people started putting the pieces together better."

And physicians committed to researching and providing treating for one of these strange maladies often push into medical frontiers to improve the lives of their patients.

The Stanford conference on complex regional pain syndrome, held May 30 and May 31, drew dozens of experts from a variety of disciplines. The conference yielded a consensus paper on better diagnoses and optimal treatment for the condition, which emphasizes physical therapy with the use of pain medications to ease the initial agony of exercise, the same therapy Krane used with Kaycee. Krane said the statement will be published in a leading pediatric medical journal.

These kinds of conferences are vital for improving the medical profession's track record for diagnosing unique diseases, said Groft. And even though doctors often have few if any treatments to offer, the diagnosis allows patients and their families to band with others with the condition to seek the best treatments and advocate for research.

"Many advocacy groups can help patients live a little better life," said Groft.

Furthermore, the NIH budget for rare disease research is robust, he added. Of the $29 billion awarded by the NIH last year for medical research grants, $4 billion, or 18 percent, went to studying rare diseases. The grants often fund clinical trials that give patients with few or no options a chance to try potential treatments, Groft emphasized.

"That's one of the messages we'd like to get out," he said. "People can get information on on-going clinical studies, as well as completed ones. So there can be hope for people with rare diseases."

Krane pointed hopefully to a future in which genetic tests of blood samples will quickly provide answers to the questions that now vex physicians encountering patients with mysterious ailments.

"Thirty years from now," he speculated, "all that work is going to be done for us. Someone is going to plug some blood into a gene array and the answer will pop out."

Until and if such swift diagnoses of rare diseases come to pass, Groft said those with disorders that defy treatment can best cope with their frustration and fear by seeking access to specialists.

"No one can be expected to know that many disorders," he said of the rare diseases so far identified. "We encourage patients to be referred upward in the medical system to specialists."

Kaycee and her mother consider themselves extraordinarily fortunate to have found Krane and to have the funds for the medical costs.

Donna Antosiak calls Krane "my favorite person in the whole wide world," while Kaycee said she doubts she would be walking today without his treatment.

"I probably would have gone crazy from the pain," she said.

As for those with less access to sophisticated medical care or with fewer financial resources, Kaycee shuddered to consider their fate: "I wouldn't want to find out what happens to them," she said.

For information on NIH-approved clinical trials for treatments for rare diseases, visit http://www.clinicaltrials.gov.

Contact Suzanne Bohan at sbohan@angnewspapers.com or (650) 348-4324.