WEDNESDAY, April 20 (HealthDay News) -- Researchers have
identified a genetic variant that's found in at least 59 percent of
those who have pulmonary fibrosis, a deadly lung disease that
typically kills within a few years of diagnosis.
Those with the gene variant had nearly 7 to 22 times the risk of
contracting the lethal disease.
For the study, the researchers did a genome-wide linkage scan of
82 families with pulmonary fibrosis of an unknown cause. This type
of scan typically looks at how inheritance patterns of multiple
affected families are related to several hundred markers throughout
The researchers zeroed in on chromosome 11, where they found a
common gene variant.
The researchers then compared the results to the genomes of 83
people with familial pulmonary fibrosis (meaning it runs in their
family), 492 people with idiopathic pulmonary fibrosis (the type
for which there's no known cause) and 322 people without lung
More genetic mapping showed that about 59 percent of people who
have familial pulmonary fibrosis (also known as familial
interstitial pneumonia) and 67 percent of those with the idiopathic
type had the particular variant, or polymorphism.
Only 18 percent of those who did not have lung disease had that
Pulmonary fibrosis involves rapid and progressive scarring of
the lungs, making it increasingly difficult to breathe. It develops
mostly in middle-age and older adults, according to the Coalition
for Pulmonary Fibrosis. Each year, about 40,000 people in the
United States die of the disease.
"This gene variant contributes to the development of disease in 60 percent of patients with pulmonary fibrosis," said the study's senior author, Dr. David Schwartz, chairman of the department of medicine at the University of Colorado and director of the Center for Genes, Environment & Health at National Jewish Health in Denver.
So what does the MUC5B gene do in the body? It is involved with
mucus production it codes for it, in fact -- and is expressed in
the air sacs deep within the lungs.
In people with the variant who had pulmonary fibrosis,
expression of the MUC5B protein was 14.1 times higher than in those
without lung disease. The protein produced by MUC5B was also found
at higher concentrations in the injured sections.
Though pulmonary fibrosis was believed to be a problem with the
lung tissue itself, the new research suggests that pulmonary
fibrosis is actually a problem of the airways, Schwartz said.
That could open the door to new treatment possibilities,
including inhaled medications, he said.
"We don't have an effective treatment for the disease, and we don't have an effective treatment because we've been focusing on the wrong target," Schwartz said. "This discovery will help us focus on the right target and develop or try treatments that are directed at the mucus in the lung and the repair process in the lung associated with excessive mucus production.
The research is reported in the April 21 issue of the
New England Journal of Medicine.
Dr. Marylyn Glassberg, an associate professor of medicine and
surgery and director of the Interstitial Lung Disease Program at
the University of Miami Miller School of Medicine, said that the
researchers have found a strong association, but they haven't
"They make a strong case that this could be a very important contributor in terms of the development of the disease," Glassberg said.
But the findings do not explain why about 9 percent of people
without lung disease have the variant but not the disease or what
triggers the disease in those who get it.
It's likely that other genes, illnesses or environmental factors
play a role, Glassberg said. Conditions such as lupus and
scleroderma are risk factors for the disease, as is smoking and air
pollution, she said.
"This is a very important study, but it's not causative," Glassberg said.
It's possible that too much MUC5B protein makes it increasingly
difficult for the mucus in the lung to clear foreign particles,
such as cigarette smoke, dust and air pollution or to repair itself
when it's exposed to pollution and other irritants, Schwartz
Another theory is that the MUC5B polymorphism may result in the
protein being produced in parts of the lung where it shouldn't be,
so that it acts not as a protector but as a toxin.
Besides opening the door to other treatments, Schwartz said, the
study's findings might also enable genetic testing of people who
have the disease in their family.
In addition, researchers found that those who'd inherited one
copy of the variant from their parents were seven to nine times
more likely to have disease and those with two copies of the
variant had up to a nearly 22-fold increased risk.
A genetic test for pulmonary fibrosis would be welcomed by many,
such as Teresa Barnes, vice president of patient outreach and
program support at the Coalition for Pulmonary Fibrosis. Her father
was diagnosed with the disease in 2002 and died within two years.
Within a few years, his sister and two other brothers also died of
"It's excruciating to watch," Barnes said. "Someone you love is suffocating. You can't make it go away. You can't stop it. You feel really helpless, and you feel really hopeless."
Barnes, who has a 7-month-old daughter, said she wonders if she
or her daughter are destined to get the disease.
"It scares the life out of all of us," Barnes said. "If 100 percent of the generation before you died from something, believe me, you're afraid."
The Coalition for Pulmonary Fibrosis has more about
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