Familial pulmonary fibrosis strikes at a younger age and progresses faster

Familial pulmonary fibrosis (FPF) makes up a notable portion of all cases of interstitial lung disease, disorders marked by scarring in the lungs, and tends to appear differently from non-familial versions of the disease, a large, multicenter study has found.

While survival outcomes were similar between the two groups, patients with the familial form of the disease tended to be younger at diagnosis and experienced a faster decline in lung function.

“These findings support routine family history ascertainment as a simple prognostic tool and highlight the need for improved screening, genetic integration, and tailored management strategies in familial disease,” researchers wrote.

The study, “Clinical and Radiologic Characteristics of Familial Pulmonary Fibrosis,” was published in the Annals of the American Thoracic Society.

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Defining the disease and registry data

FPF occurs when two or more family members, often a parent, child, or sibling, develop interstitial lung disease (ILD), a condition marked by progressive inflammation and scarring (fibrosis) in the lungs.

However, the prevalence and clinical significance of FPF in groups of ILD patients are not well-established.

“Given recent guidelines recommending family member screening for FPF, a better understanding of the prevalence and [features] of FPF is essential for proper health systems planning and resource allocation,” the researchers wrote.

With this in mind, the team accessed data from the Canadian Registry for Pulmonary Fibrosis. In total, 5,375 people with fibrotic ILD were included in the primary analysis group, and 719 (13%) of them were classified as having FPF.

Of those with FPF, 18% had idiopathic pulmonary fibrosis (IPF, a form of the disease without a clear cause), 12% had fibrotic hypersensitivity pneumonitis (fHP, lung scarring caused by an immune reaction to inhaled substances), and 9% had SARD-ILD, which stands for Systemic Autoimmune Rheumatic Diseases and refers to scarring linked to autoimmune conditions.

Compared with those with sporadic disease, FPF patients were younger, more likely to be female, less likely to have a history of smoking, and, at registry enrollment (baseline), had a higher DLCO%, a measure of how well the lungs transfer gas into the blood.

Immunosuppressants were prescribed less often to FPF patients than to sporadic ILD patients (46% vs. 53%). Conversely, antifibrotic therapy was prescribed more often to FPF patients in the SARD-ILD, fHP, and unclassifiable ILD subgroups compared with their sporadic counterparts. The rates of antifibrotic use were similar between FPF-IPF and sporadic IPF patients.

Overall, the mean annual rate of lung function decline was significantly greater in FPF patients compared with those with sporadic ILD. However, when examining individual diagnostic subgroups, there were no differences in lung decline between FPF and sporadic cases across the four subtypes examined (IPF, SARD-ILD, fHP, or unclassifiable ILD).

While FPF patients were more often referred for a lung transplant, there was no significant difference in transplant-free survival, meaning the time patients lived without needing a transplant, between FPF and sporadic ILD.

Analyzing CT scan findings

The researchers then analyzed the chest CT scans of 1,519 patients, 197 (13%) of whom had FPF. When radiologists assigned imaging patterns directly, a higher proportion of FPF cases were classified as the usual interstitial pneumonia (UIP) pattern than in sporadic ILD (42.6% vs. 33.4%). This is a specific scarring pattern seen on imaging.

After adjusting for relevant factors, FPF status was not associated with differences in certain CT parameters. This included honeycombing, a pattern of clustered air spaces indicating advanced scarring; reticulation, a net-like pattern of lung changes; and traction bronchiectasis, an abnormal widening of the airways due to surrounding scar tissue.

FPF patients showed a lower overall percentage of ground-glass opacity (a hazy appearance on imaging indicating less advanced changes) than sporadic cases. Among patients with a definite UIP pattern, those with FPF had a greater extent of reticulation and traction bronchiectasis than patients with sporadic ILD.

When the team compared CT findings with clinical data, the mean annual rate of lung function decline was greater in patients with a radiologist-assigned UIP pattern than in those with a non-UIP pattern, in both FPF (1.78%) and sporadic ILD (1%) patients.

Among patients with a UIP pattern specifically, FPF patients showed a faster annual lung function decline than sporadic disease patients (2.84% vs. 1.91%). The rate of DLCO% decline was faster in the UIP group compared to the non-UIP group, regardless of whether a patient had FPF or sporadic ILD.

“In this large multicenter registry, FPF was identified in 13% of patients and was associated with earlier presentation in key subgroups, a higher prevalence of UIP patterns, and accelerated [lung function] decline, particularly among those with UIP, despite comparable transplant-free survival,” the researchers concluded.