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Long-Held Cystic Fibrosis Theory Challenged

Study finds patients may produce too little mucus, not too much

FRIDAY, July 2, 2004 (HealthDayNews) -- Could a new finding turn a longstanding theory about the nature of cystic fibrosis (CF) on its head?

For years, doctors have blamed the life-threatening lung infections suffered by those with CF on the excess production of airway mucus. That notion has never been proven conclusively. Now, researchers at Wake Forest Baptist Medical Center say the problem may actually be the opposite: too little airway mucus.

If the research bears out -- the study was small -- it could lead the way to more effective treatments for the disorder, which affects about 30,000 children and adults in the United States. The study appears in the July 1 online issue of the American Journal of Respiratory Cell and Molecular Biology.

The median survival for a person with cystic fibrosis is 33.4 years, according to the Cystic Fibrosis Foundation.

Traditional thinking goes this way, explained Dr. Bruce Rubin, a professor of pediatrics at Wake Forest and a corresponding author on the study: "You make too much mucus, it gets plugged up [in the airway], the bacteria that are there don't get cleared out, and you get infections." While mucus normally lubricates and protects the respiratory system, those with CF have chronic coughs and infections, and it has been assumed the airways were too full of mucus.

But the new thinking, said Rubin, goes thusly: "Mucus is good for you, it's your friend. The problem in cystic fibrosis is it doesn't get into the airway. It may be made in the cell, but not getting out of the cells into the airway. If it goes out into the airway, it would prevent the infection in the first place."

Rubin and his team, led by Dr. Markus Henke, at the time of research a fellowship student in Rubin's lab but now at Philipps-University in Germany, collected sputum from 12 patients with cystic fibrosis and 11 without the lung disease, then analyzed the contents.

"The results really surprised us," Rubin said.

Those with CF had substantially less of the two major proteins that form mucus, called MUC5AC and MUC5B, than those with healthy lungs.

The substance clogging the lungs of the CF patients isn't mucus at all, they suggest. "What's in the cystic fibrosis lung is basically pus," Rubin says. "It's a lot of inflammatory cells, broken down."

The mucus may actually protect the airway from infection, Rubin speculates. If that bears out, he said, that may lead to a treatment for cystic fibrosis -- increasing the mucus in the airway early on to help prevent the infection.

Another expert lauds the study, but cautions it might not be met with total agreement.

"I thought it was an interesting study, I thought it was carefully done," said Dr. Judy Voynow, a pediatric pulmonologist and associate professor of pediatrics at Duke University Medical Center. "I think it is going to be controversial."

"Other scientists have also found in cystic fibrosis mucus there is a high concentration of DNA, other proteins called proteoglycans," Voynow added. "So we already know that cystic fibrosis mucus is complicated, and we may need multiple approaches to get rid of it."

If the new research eventually points to a new therapy, it would be welcome, Voynow said.

More information

Learn about the disease from the Cystic Fibrosis Foundation.

SOURCES: Judy Voynow, M.D., associate professor, pediatrics, and pediatric pulmonologist, Duke University Medical Center, Durham, N.C.; Bruce Rubin, M.D., professor, pediatrics, Wake Forest University School of Medicine, Winston-Salem, N.C.; July 1, 2004, American Journal of Respiratory Cell and Molecular Biology online
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