Is Interstitial Lung Disease Hereditary?

Some forms of interstitial lung disease are hereditary, though most cases arise from a tangled mix of genetic susceptibility and environmental exposures rather than a single inherited mutation. When pulmonary fibrosis runs in families, researchers call it familial pulmonary fibrosis, and it accounts for a meaningful minority of all fibrotic lung disease cases. More than 30 genes have been linked to various forms of ILD, with inheritance patterns ranging from dominant to recessive to X-linked. The genetics turn out to matter not just for understanding who gets sick, but for predicting how fast the disease progresses and which treatments work.

What Familial Pulmonary Fibrosis Means

Interstitial lung disease is not one disease but a large umbrella covering more than 200 conditions that scar or inflame the tissue between the air sacs of the lungs. When researchers talk about hereditary ILD, they usually focus on the fibrotic forms, especially idiopathic pulmonary fibrosis (IPF), which is the most common and most deadly subtype. Familial pulmonary fibrosis (FPF) is generally defined as fibrotic ILD occurring in at least two first- or second-degree blood relatives.¹ That definition is broader than many people expect: the two affected relatives do not need to have the exact same type of fibrotic lung disease. One might have IPF, and the other might have a different fibrotic pattern entirely.

Patients with FPF tend to develop symptoms at a younger age than people with the sporadic (non-familial) form, and they tend to fare worse. Survival is shorter on average compared to sporadic IPF, even though the diseases can look similar on imaging and biopsy.² This difference in outcomes is one of the reasons genetic evaluation has become increasingly important in ILD clinics.

The MUC5B Variant and Common Genetic Risk

The single strongest and most consistently replicated genetic risk factor for IPF is a variant in the promoter region of a gene called MUC5B. This gene encodes a mucin protein, one of the gel-forming molecules that make up the mucus lining your airways. A particular change near the gene’s start site (a promoter polymorphism) dramatically increases the odds of developing pulmonary fibrosis. In one landmark study, people who carried one copy of this variant had roughly nine times the odds of developing IPF, and those who carried two copies had about 22 times the odds, compared to people without it.³ The variant was similarly enriched in families with pulmonary fibrosis.

What makes MUC5B unusual among disease-risk variants is how common it is in the general population. About 9% of control subjects carried it in the same study, meaning millions of people walk around with this variant and never develop lung disease. The variant appears to increase MUC5B expression in the small airways and in the honeycomb-like cysts that characterize advanced fibrosis.⁴ Together with other common genetic variants, MUC5B accounts for roughly a third of overall disease risk for IPF. That leaves plenty of room for environmental triggers, aging, and rarer mutations to fill in the rest.

Recent proteomic work has started to reveal what the MUC5B variant actually does inside the lung before fibrosis sets in. In non-fibrotic lung tissue from carriers, the variant was linked to changes in over 100 proteins, including increases in signaling molecules involved in inflammation and decreases in proteins that maintain cell junctions.⁵ In other words, the variant appears to quietly reshape the molecular landscape of the lung long before any scarring is visible.

Telomere Genes and the Biology of Aging Lungs

If MUC5B is the most common genetic contributor to IPF risk, mutations in telomere-maintenance genes are the most common monogenic cause of familial pulmonary fibrosis. Telomeres are the protective caps at the ends of chromosomes, and they shorten each time a cell divides. When telomeres get critically short, cells stop dividing or die, which is a problem in organs like the lungs that need a steady supply of fresh cells to repair damage.

The first telomere genes linked to pulmonary fibrosis were TERT and TERC, which encode the two core components of telomerase, the enzyme that rebuilds telomeres. In families carrying mutations in these genes, affected members had markedly shorter telomeres than their unaffected relatives of the same age.⁶ Individually, each TERT or TERC mutation is rare, but collectively TERT mutations are the most frequently identified genetic defect in familial pulmonary fibrosis.⁷ One study found TERT or TERC mutations in about 15% of familial cases and identified additional mutations among patients with clinical features of a telomere syndrome.⁸

The list of telomere-related genes keeps growing. RTEL1, a DNA helicase involved in telomere stability and DNA repair, has been found mutated in several pulmonary fibrosis families, with carriers showing short telomeres just as in TERT/TERC families.⁹ PARN, a gene that was not even connected to telomere biology before pulmonary fibrosis research drew attention to it, was identified through large-scale gene-burden analysis. Together PARN and RTEL1 explain an additional 7% of familial cases.¹⁰ The inheritance of short telomeres in these families does not always follow simple rules: some family members inherit the short-telomere state epigenetically, meaning the telomere length can be passed down even without the specific gene mutation.

Surfactant Gene Mutations

The lung’s air sacs are coated with surfactant, a thin layer of proteins and fats that keeps them from collapsing. Mutations in the genes responsible for producing or transporting surfactant cause a different branch of hereditary ILD, one that often shows up much earlier in life than fibrosis linked to telomere genes.

SFTPC mutations, which affect the surfactant protein C gene, are inherited in an autosomal dominant pattern or can arise as brand-new (de novo) mutations. The clinical range is enormous: some affected newborns develop fatal respiratory distress, while others coast into adulthood before chronic lung disease becomes apparent.¹¹ Because a single copy of the mutated gene is enough to cause disease, an affected parent has a 50% chance of passing the mutation to each child, though how severely that child will be affected is unpredictable.

ABCA3 mutations work differently. This gene encodes a transporter that moves fats into the surfactant-producing compartments of lung cells. ABCA3-related disease is autosomal recessive, meaning a child needs to inherit a faulty copy from each parent to develop the condition.¹² The severity depends heavily on the specific mutations involved. In one large registry study of children carrying two ABCA3 variants, those whose mutations left some residual protein function had far better survival beyond the first year of life than those whose mutations eliminated function entirely.¹³ Some children with milder mutation combinations go on to develop chronic childhood or even adult-onset ILD rather than neonatal crisis.

Hermansky-Pudlak Syndrome

Some inherited conditions cause ILD as one feature among many. Hermansky-Pudlak syndrome (HPS) is a rare genetic disorder that affects how cells make and transport small storage compartments called lysosomes and related organelles. People with HPS typically have reduced skin and eye pigmentation, a bleeding tendency because their platelets do not work normally, and, in certain subtypes, progressive pulmonary fibrosis. HPS pulmonary fibrosis develops in virtually all patients with the HPS-1 subtype, and its progression resembles IPF.¹⁴ Other subtypes, including HPS-2 and HPS-4, also carry a risk of lung fibrosis, though the risk is not as universal.¹⁵

HPS is inherited in an autosomal recessive fashion, and it is concentrated in certain populations, particularly people of Puerto Rican descent, where a founder mutation makes it far more common than elsewhere. Recognizing HPS matters because the pulmonary fibrosis it causes looks a lot like IPF on a CT scan, and if clinicians do not notice the other features of the syndrome, patients can be misdiagnosed and miss out on appropriate management.

When Autoimmune Disease Shares Genetic Ground With Fibrosis

ILD does not always arrive on its own. It frequently complicates autoimmune conditions such as rheumatoid arthritis, and researchers have found that the genetic overlap between autoimmune-associated ILD and familial pulmonary fibrosis is more than coincidence. In a study of over 100 patients with rheumatoid arthritis-associated ILD (RA-ILD), about 12% carried mutations in genes previously linked to familial pulmonary fibrosis, including TERT, RTEL1, PARN, and SFTPC. Those mutations were roughly three times as common in RA-ILD patients as in controls.¹⁶ The MUC5B variant also turns up more often in RA-ILD patients than in the general population.¹⁷

This overlap suggests that the same genetic vulnerabilities that predispose some families to pulmonary fibrosis can also tip the scales toward lung involvement in people who already have an autoimmune disease. It is an area where the line between “hereditary” and “acquired” ILD gets blurry: the autoimmune condition itself has a genetic component, and the lung fibrosis riding along with it has a partly independent genetic basis.

How Genetics Shape Prognosis and Treatment

Knowing a patient’s genetic background is not just academic. Telomere length, in particular, has emerged as a practical biomarker. Patients with interstitial lung disease whose blood-cell telomeres fall below the 10th percentile for their age lose lung function faster and have worse transplant-free survival. In one study, those with very short telomeres lost lung function at a rate roughly seven times faster per year than patients with longer telomeres.¹⁸ Telomere shortening has been described as a biomarker that predicts disease course independently of other clinical factors.¹⁹

Genetics also influence what happens after lung transplantation. Patients with telomere-biology disorders who undergo transplant tend to develop more complications, both in the transplanted lung and elsewhere in the body. Standard immunosuppressive drugs, which are essential after transplant to prevent rejection, can be poorly tolerated because the same short-telomere biology that damaged the lungs also affects the bone marrow, making patients vulnerable to dangerously low blood counts.²⁰ Some transplant centers have experimented with alternative immunosuppressive regimens for these patients, though early results suggest trade-offs such as a higher risk of certain viral infections.²¹ Precision treatments targeted at specific genetic variants are a stated goal of the field, but they remain largely aspirational for now.²²

Screening Relatives Before Symptoms Appear

If a family member has pulmonary fibrosis, should their siblings and children be screened? The answer is leaning toward yes, though the practice is still not standard everywhere. In a prospective study that tracked first-degree relatives of familial pulmonary fibrosis patients with high-resolution CT scans, about 15% of those who had no visible lung abnormalities at enrollment went on to develop progressive changes over time. Among those who already had mild abnormalities at baseline, roughly two-thirds showed progression, and those with moderate abnormalities at baseline had even higher odds of worsening.²³ Quantitative CT analysis can pick up subtle changes in lung density, small-vessel volume, and early fibrosis that the human eye might miss.²⁴

The goal of early screening is to catch fibrosis at a stage when interventions such as antifibrotic drugs might slow progression, rather than starting treatment after significant scarring has already accumulated. Whether early antifibrotic treatment in pre-symptomatic individuals actually improves long-term outcomes is still being studied, but the ability to detect the disease earlier is already established.

Genetic Testing in Practice

Genetic testing for ILD is increasingly available, but it does not yield a clear answer for everyone. In a large molecular investigation of nearly 700 unrelated patients with early-onset ILD, pathogenic gene variants that explained the disease were found in about 14% of cases overall.²⁵ The yield jumped substantially in certain clinical scenarios. Newborns with unexplained respiratory distress, patients with pulmonary alveolar proteinosis, and those with a family history of both ILD and lung cancer were far more likely to have a diagnosable genetic cause.²⁶ This means genetic testing is most productive when clinicians select patients whose presentation suggests a higher likelihood of a monogenic cause.

Epigenetic changes add another layer of complexity. Beyond the DNA sequence itself, modifications like DNA methylation and histone changes can turn genes up or down without altering the underlying code, and these alterations are gaining attention as contributors to fibrosis.²⁷ Epigenetic changes can be influenced by environmental exposures like cigarette smoke, which is itself an established risk factor for IPF.²⁸ So even when a clear genetic variant is present, lifestyle and environmental factors still shape whether and when disease appears.

What Families Worry About When Genetic Testing Is Offered

Genetic testing in a family affected by pulmonary fibrosis is not just a medical decision. It comes with emotional weight. In one study that assessed the psychological impact on undiagnosed first-degree relatives who underwent screening, more than 90% reported no or only mild regret about participating. Interestingly, what troubled people most was not their genetic or telomere results but the discovery of functional or imaging abnormalities, like reduced gas exchange in the lungs or early scarring visible on CT.²⁹

Practical concerns matter too. In a mixed-methods study of patients and their relatives, about 60% of first-degree relatives worried about insurance implications and personal stress related to genetic results. About 29% of relatives said they would change their health behavior based on results, for instance by quitting smoking or pursuing more frequent check-ups.³⁰ These fears are not irrational. While legal protections against genetic discrimination exist in many countries, they do not always cover life insurance or disability insurance, and the specifics vary by jurisdiction. Genetic counseling before and after testing helps families navigate these decisions, but access to counselors with ILD-specific expertise remains uneven.

The Pediatric Picture

Hereditary ILD looks different in children than in adults. More than 30 genes with varying inheritance patterns have been linked to pediatric ILD, spanning surfactant metabolism, telomere maintenance, immune regulation, and epithelial repair.³¹ Children are more likely than adults to have a clearly identifiable monogenic cause, particularly when disease appears in the neonatal period or early infancy. Surfactant gene mutations, especially SFTPC and ABCA3, dominate the pediatric landscape. In contrast, adult-onset hereditary ILD leans more heavily on telomere-biology genes and polygenic risk variants like MUC5B.

This distinction has practical implications for genetic testing. A newborn with unexplained respiratory failure and full-term birth has a relatively high probability of carrying a surfactant gene mutation, making early genetic testing especially worthwhile. An adult diagnosed with IPF at 65 may carry common risk variants, but the chances of finding a single causative mutation are lower unless there is a clear family history or suggestive extra-pulmonary features like early graying, low blood counts, or liver disease, all of which can signal an underlying telomere disorder.