Pulmonary fibrosis has a genetic component in a meaningful number of cases. About 10% of idiopathic pulmonary fibrosis (IPF) cases are classified as familial, meaning the disease runs in families with identifiable genetic links. The remaining 90% are considered sporadic, but even many sporadic cases involve genetic variants that increase susceptibility. So while pulmonary fibrosis isn’t always inherited in a straightforward way, genetics plays a role across the spectrum of the disease.
How Genetics Contributes to Pulmonary Fibrosis
Two categories of genetic involvement drive pulmonary fibrosis. The first is rare, high-impact mutations in single genes that can directly cause the disease within families. The second is common genetic variants that don’t cause the disease on their own but raise your risk, especially when combined with environmental exposures like smoking or dust inhalation.
The most well-known risk genes fall into two groups: those involved in maintaining telomeres (the protective caps on the ends of chromosomes) and those involved in producing surfactant (the slippery coating that keeps your lung air sacs from collapsing). Mutations in the telomere-related genes TERT and TERC are among the most frequently identified in familial cases. A common variant in a gene called MUC5B, which controls mucus production in the airways, is the single strongest genetic risk factor for IPF in the general population.
The MUC5B Variant and Population Risk
A specific variant in the MUC5B gene’s promoter region has been studied extensively. In Caucasian populations, roughly 42% of people with IPF carry this risk variant, compared to about 11% of healthy controls. A large meta-analysis found that carrying even one copy of the variant increases the odds of developing IPF by about fourfold, and carrying two copies raises the odds roughly tenfold. In East Asian populations, the variant is much rarer, appearing in about 3% of IPF patients and less than 1% of controls, but it still carries a significant risk increase when present.
This matters because the MUC5B variant is common enough that many people carry it without ever developing lung disease. It’s a susceptibility factor, not a guarantee. Whether it leads to fibrosis depends on other genetic variants you carry, your age, and your environmental exposures over a lifetime.
Telomere Genes and How They Damage the Lungs
Your lungs constantly repair themselves. The tiny air sacs (alveoli) rely on stem cells to regenerate their lining. These stem cells need functioning telomeres to keep dividing. Telomeres naturally shorten with each cell division, but an enzyme called telomerase rebuilds them. When mutations in genes like TERT or TERC reduce telomerase activity, telomeres shorten faster than they should. The lung’s stem cells lose their ability to regenerate, and damaged tissue gets replaced with stiff scar tissue instead of healthy cells.
This scarring process involves a cascade of signals. As lung stem cells become senescent (essentially worn out and unable to divide), they release inflammatory molecules that change the local environment. One key change is increased signaling from a growth factor called TGF-beta, which promotes the deposit of dense, fibrous tissue in the spaces between air sacs. Over time, this makes the lungs progressively stiffer and less able to exchange oxygen.
Research in animal models has confirmed this pathway directly. When scientists disable the protective proteins on telomeres in mouse lung stem cells, the animals develop spontaneous pulmonary fibrosis, losing roughly two-thirds of their critical stem cells and showing widespread cellular aging and cell death in the lungs.
Inheritance Patterns in Families
When pulmonary fibrosis is caused by a single gene mutation, it most commonly follows an autosomal dominant pattern. This means inheriting just one copy of the mutated gene from one parent can be enough to cause disease. The major telomere genes (TERT, TERC, RTEL1, PARN) and the surfactant protein genes (SFTPC, SFTPA1, SFTPA2) all follow this pattern. One gene, ABCA3, follows an autosomal recessive pattern, requiring mutations from both parents. Another, DKC1, is X-linked.
A critical detail is that these mutations show “incomplete penetrance and variable expressivity.” In plain terms, not everyone who inherits the mutation will develop the disease, and those who do may develop it at different ages and with different severity. Two siblings with the same TERT mutation might have very different outcomes. One might develop fibrosis in their 50s, while the other stays healthy into their 70s. This unpredictability makes familial pulmonary fibrosis difficult to predict on an individual level, even when the genetic cause is known.
Genes and Environment Working Together
Even in genetically susceptible people, environmental factors often play a triggering role. Cigarette smoking is the most strongly associated risk factor for both sporadic and familial pulmonary fibrosis. Occupational exposures to metal dust and wood dust also significantly raise risk, independent of smoking.
The interaction between genes and environment can be quite specific. Research has identified a genetic variant in the promoter region of a tissue-remodeling gene where one particular genotype is overrepresented in smokers who develop IPF, suggesting that this variant and cigarette smoke work together to increase susceptibility. Smoking also causes chemical changes to how genes are read and expressed (epigenetic changes), reducing the activity of genes that normally protect against fibrosis. These changes promote scarring even in people who might not have developed the disease from genetics alone.
This gene-environment interplay is why pulmonary fibrosis is often described as a “complex disease,” one where the cause is a combination of genetic effects and environmental influences rather than a single clear trigger.
Genetic Forms in Children
Pulmonary fibrosis in children is rare, but when it occurs, it’s more likely to have a clear genetic cause. Mutations in genes that produce surfactant proteins B and C are the primary culprits. Surfactant is the substance that coats the inside of your air sacs and keeps them from sticking shut when you breathe out.
Mutations in the SP-B gene typically cause severe, progressive respiratory failure in newborns, often fatal within the first three to six months without a lung transplant. SP-C mutations are more variable. About 10 to 15% of affected children develop symptoms in the first month of life, while another 40% show signs between one and six months, with the average onset around two to three months. Some people with SP-C mutations don’t develop lung disease until adulthood, making this one of the genes that can bridge childhood and adult forms of pulmonary fibrosis.
Familial Cases Progress Faster
Having a family history of pulmonary fibrosis isn’t just a risk factor for developing the disease. It also predicts a worse outcome. A study published in the journal Chest found that patients with familial IPF had an 80% increased risk of death or need for lung transplant compared to patients with sporadic IPF. For familial non-IPF forms of interstitial lung disease, the increased risk was even higher: twofold compared to sporadic cases.
One striking finding was that patients with familial non-IPF lung disease had survival outcomes similar to patients with sporadic IPF, a disease known for its poor prognosis. This suggests that family history alone, regardless of the specific diagnosis, should prompt earlier and more aggressive treatment consideration.
Screening for At-Risk Family Members
If you have a close relative with pulmonary fibrosis, you may benefit from screening even if you have no symptoms. First-degree relatives of people with familial pulmonary fibrosis are considered high-risk for developing the disease themselves. Clinical protocols at specialized centers include a chest CT scan every five years, along with annual checkups that include lung function tests, blood work, and a physical exam for relatives over 18.
The goal of screening isn’t to predict with certainty who will develop fibrosis. It’s to catch early signs of lung scarring before symptoms appear, when interventions may be more effective. Genetic testing can identify whether you carry a known mutation, but because of incomplete penetrance, a positive genetic test doesn’t mean you’ll definitely develop the disease. It does mean closer monitoring is worthwhile.