Pulmonary fibrosis (PF) is characterized by the accumulation of scar tissue (fibrosis) in the lungs. Idiopathic pulmonary fibrosis (IPF), a form of the disease that lacks a clear cause, is the most common form of PF.
Sometimes, PF can run in families, in which case it is sometimes referred to as familial pulmonary fibrosis. The most commonly used definition of familial pulmonary fibrosis is when two or more family members — often a parent, child, or sibling — are diagnosed with IPF or similar lung-scarring conditions.
Familial pulmonary fibrosis is very rare, with only about 100 families documented to have this condition, as reported in a study published in 2013.
Familial pulmonary fibrosis genetics
Because familial pulmonary fibrosis, by definition, affects people who are closely related from a biologic standpoint, genetic factors are presumed to play a major role in the development of the disease. Environmental and lifestyle factors, such as smoking cigarettes, also may influence the formation of scar tissue.
Specific mutations, particularly those affecting telomerase or pulmonary surfactants, have been linked with this type of PF. However, in most cases the disease-associated mutation may be unknown.
Telomerase-related mutations
Telomerase is an enzyme responsible for maintaining the integrity of telomeres — structures that act like “caps” on the ends of chromosomes, helping to prevent DNA damage. As the body ages and cells continually divide, telomeres tend to become increasingly shorter. At a certain point, too-short telomeres are thought to drive cell death.
Mutations in telomerase-related genes have been linked to familial pulmonary fibrosis, and also to IPF. The most common of these mutations affect the genes TERC and TERT, each of which provides instructions to make part of the telomerase enzyme. Other telomerase-related genes that have been linked to this type of PF include DKC1, NAF1, RTEL1, PARN, TINF2, and ZCCHC8.
Surfactant-related mutations
In the lungs, air comes into contact with body fluids, which creates surface tension. To lessen this tension and make breathing easier and more efficient, lungs produce specialized molecules called surfactants.
Mutations in genes associated with surfactant production, such as SFTPC and SFTPA1, also have been associated with familial pulmonary fibrosis.
Symptoms and diagnosis
Symptoms of familial pulmonary fibrosis are generally similar to those seen in other forms of PF. These include shortness of breath, coughing, and fatigue.
Some studies have suggested that people with this type of pulmonary fibrosis tend to have more severe disease, and an earlier age at onset, than those with IPF. However, symptom severity and age at onset varies substantially from person to person and family to family.
A variety of diagnostic tests may help identify lung scarring. In addition, genetic testing to look for disease-associated mutations may be performed. Yet, genetic mutations associated with familial pulmonary fibrosis usually are found in only up to 30% of patients.
Treatment and prognosis
Treatment options for those with familial pulmonary fibrosis are similar to those available for other forms of PF. They include the use of antifibrotic medications, oxygen therapy, pulmonary rehabilitation or, in severe cases, a lung transplant.
Genetic counseling and regular screening tests to detect emerging abnormalities may be considered for people with relatives who have been diagnosed with familial PF. Early detection and treatment might lead to a better prognosis.
Last updated: Oct. 29, 2021
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