Early last week, Walter Breidigan felt tired and had a funny sensation of dizziness, like his blood pressure was plummeting down. The symptoms were familiar. He knew if he didn't get to the St. Clair Hospital emergency room fairly quickly he was going to have a violent, potentially deadly, episode of systemic capillary leak syndrome.

If you're wondering what that is, don't feel bad. Even Mayo Clinic in Rochester, Minn., has seen just 25 patients with the disorder since 1980. And that number, the clinic says on its website, is more than any other medical center.

Mr. Breidigan, a 53-year-old electrical engineer from Bethel Park, was the first person to show up at the St. Clair ER with the disorder, which also is known as Clarkson's disease.

That was back in 2005, and it wasn't until Mr. Breidigan had a second episode nearly three years later that pulmonary/critical care specialist Gregory Fino was able to diagnose it.

Mr. Breidigan's story will be told Monday in an episode of the Discovery Health Channel's show "Mystery Diagnosis." Mr. Breidigan plays himself in many of the scenes, which were filmed here in October.

It is a tale of a disorder of unknown cause and unknown cure, one that the Mayo Clinic website says is "characterized by massive leaking of plasma from blood vessels into adjacent body cavities and muscles. The leakage causes a sharp drop in blood pressure, which can lead to organ failure and death."

Between 2005 and 2008, Mr. Breidigan had three major episodes of the disorder, which he says has a mortality rate of five years, an anniversary he passed up Feb. 4.

The first two times, he said, his kidneys failed to the point of dialysis but then resumed function within a few days. If they hadn't, he said, his liver would have been next to go into decline.

The first time he was sickened by the ailment, no one had a clue what was wrong.

He had awakened Feb. 4, 2005, with flu-like symptoms and then worsened from there. There were dizziness, extremely low blood pressure, terrible leg pain. At the time, the doctors suspected a flesh-eating disease, but the tests were negative. Eventually he filled up with about 100 pounds of fluid and was unrecognizable.

"They let me stay there with him until 2 or 3 in the morning, and he was starting to swell," said his wife, Nancy. "When I returned at 9, I walked back out. I truly thought they'd moved him. I asked the nurse, 'What did you do with Walt?' and she said, 'That's him.' I said, 'No way that's him.' Not only had he gained all that weight, but he looked like he'd aged 10 years."

"I wish we'd had a [Dr. Gregory] House," Mr. Breidigan said, referring to the title character in the popular television series. "They contacted doctors all over the world and had probably 12 specialists look at me. They came in constantly."

They treated his low blood pressure with fluids, but then had to use diuretics to remove the excess fluids when he swelled up, Dr. Fino said.

Eventually, the doctors concluded he had a virus. "They had no other explanation," Mr. Breidigan said.

He spent two weeks in intensive care -- he had to learn to walk again because the swelling had damaged nerves in his feet -- before going home.

Nearly three years later, on Dec. 30, 2007, his symptoms returned.

"When he said, 'Call the emergency room. It's happening again,' I said, 'This can't be happening again,' " Mrs. Breidigan said. "Next thing I knew he passed out, and then I knew it was happening again."

This time, after much computer research, Dr. Fino was able to match the symptoms of his patient to a case on the Mayo Clinic Web site and other sites. "They gave us an idea of how to treat him," Dr. Fino said. "There are very few cases ever reported, and it's not like a book treatment with a, b and c. I pulled all the information I could get, and we tried a few things."

They included using the protein albumin, diuretics, steroids and a drug called theophylline.

Then, when it happened still again in March 2008, Dr. Fino went on the offensive with the same combination. Mr. Breidigan only was in intensive care about three days.

Now he daily takes the theophylline.

"It's actually for asthma patients, but one of the doctors at Mayo discovered that it helped from getting these severe episodes," Mr. Breidigan said.

"It stabilizes all his capillaries so he doesn't leak fluid out of them," Dr. Fino said.

But the pills don't prevent what the Mayo website calls "a chronic, less intense form" of systemic capillary leak syndrome.

"The last two years it's been averaging about every couple months," Mr. Breidigan said. "I feel real tired, my blood pressure spikes up and down, and I get a real funny feeling like I'm dizzy."

When it happens, he heads to the St. Clair emergency room, as he did last week. There the staff know from his records to give him albumin intravenously. The protein helps to seal the holes in the capillaries.

There are no actual restrictions on Mr. Breidigan, except to eat healthy, which he says he's always done. And he drinks a lot of Gatorade. But his life -- and that of his family -- have been changed dramatically.

"I get tired and very dizzy if I have too much exertion," he said. "We tend to stay within two hours of the hospital. I don't travel by myself, or at least not too far, because it can happen very quickly."

And then there is the constant worry.

"It's actually tougher on my family than it is on me," Mr. Breidigan said. "When I passed out, they heard the thump. When they hear a thump now, they come running."

"With every episode, you wonder 'Is this going to be his last?' " his wife said. "I can't explain to people how stressful this is. You never get to just enjoy things."

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