One day Dennis Conway was feeling fine, and the next day he was so weak he could barely get out of bed.

The ailment baffled his doctor, who put him in a hospital intensive care unit, where his condition baffled a battery of specialists.

It took three months for doctors to come up with a diagnosis. Then, in January 2006, they told Mr. Conway he has a form of myositis, a rare autoimmune disorder that attacks and weakens muscles.

Mr. Conway, a construction worker from Gallitzin, Cambria County, has not been able to work since the disorder took over his body in October 2005. But his condition has improved since he became one of the first participants in a research project at the University of Pittsburgh School of Medicine.

The medical school has a five-year, $8 million contract from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, which is part of the National Institutes of Health, to study a treatment for myositis.

The study's principal investigator is Chester V. Oddis, a professor of medicine at the school. Dr. Oddis and researchers from Pitt's division of rheumatology and clinical immunology are leading a study that involves 36 other scientists from 18 U.S. states and four other countries -- Canada, the Czech Republic, Sweden and England.

"This is the largest study ever done on this disease," Dr. Oddis said.

Researchers are evaluating the effectiveness of a drug called rituximab, which was approved by the U.S. Food and Drug Administration in 1997 for the treatment of B-cell non-Hodgkin's lymphoma. In February 2006, it was approved for use with some adults diagnosed with rheumatoid arthritis.

Patients with two forms of myositis -- adults and children diagnosed with dermatomyositis, which causes muscle weakness and rash, and adults diagnosed with polymyositis, which is not associated with a rash -- are being enrolled in clinical trials for the study. Mr. Conway has polymyositis.

In autoimmune diseases, the body's immune system, instead of fighting infections and viruses, turns on itself and attacks muscle tissue. In some forms of myositis, the immune system may also attack skin, joints and lungs.

"We're in the second year of the trial, but we're having trouble recruiting patients," Dr. Oddis said. A total of 202 participants will be included in the study -- 152 adults and 50 children -- at 36 centers across North America and Europe. So far, only 25 percent of that total has been reached, largely because myositis is rare and difficult to diagnose and is therefore frequently misdiagnosed.

"I have about 100 myositis patients in my practice and I have as many patients with this condition as anyone," Dr. Oddis said. Approximately 10 new cases per million people will be diagnosed each year, he said.

Mr. Conway, 51, who has not had lung problems with his form of myositis, has shown slow but steady improvement since he became involved in the research project in June 2006.

"I had been in a wheelchair since October 2005 and some days I couldn't get out of bed because of muscle weakness," Mr. Conway said. "I've been having physical therapy at least three times a week since the diagnosis, then I had 14 treatments with the experimental drug. This year, I've been able to walk with crutches."

Participation in the clinical trial had an unusual benefit for Mr. Conway. After years of working construction jobs, he needed two knee replacements, but surgeons could not operate because myositis made him too weak to do the physical therapy needed to rehabilitate the joints. Finally, on Aug. 1, he was able to undergo the surgery on both knees and is doing well in rehabilitation.

Though his physical therapy and drug treatments continue, Mr. Conway said he would "love to return to work someday. I've never given up and I'm glad I went through this program."

Dr. Oddis said this research may also benefit patients with other more common autoimmune diseases, such as rheumatoid arthritis and lupus.

For more information or to enroll in the trial, call Sherrie Pryber at 412-647-3241.