There are over 200 interstitial lung diseases (ILDs). In addition to patients with idiopathic pulmonary fibrosis (IPF), a percentage of patients with other ILDs also develop progressive fibrosis of the lung during their disease course. Patients with progressive-fibrosing ILDs may show limited response to immunomodulatory therapy, worsening symptoms and lung function and, ultimately, early mortality. 

There are few data for ILDs that may present a progressive fibrosing phenotype specifically, but we believe the burden and healthcare costs associated with these conditions may be comparable to those reported in IPF. This review discusses the burden of ILDs that may present a progressive fibrosing phenotype and the factors impacting healthcare utilisation.

Acute exacerbation

Similar to IPF, acute exacerbation in other ILDs that may present a progressive fibrosing phenotype is proposed to be an acute, clinically significant, respiratory deterioration radiologically characterised by a new widespread alveolar abnormality typically occurring within 1?month in the absence of an apparent clinical cause (e.g. pneumothorax, pleural effusion or cardiac overload). Kolb et al. provide a detailed discussion of acute exacerbations.

Acute exacerbations occur infrequently, with typical annual incidences between 5% and 15% in IPF. However, they are serious events that have a high impact on patients and on costs; hospitalisation is often required, and the associated in-hospital mortality rates can be up to 50%. Acute exacerbations are associated with similar morbidity in patients with IPF and other ILDs that may present a progressive fibrosing phenotype.

Comorbidities

The likely elevation of healthcare utilisation in patients with ILD arises in part from comorbidities in patients with ILD that include cardiovascular disease, malignancy, sleep apnoea and pulmonary hypertension (PH), and contribute to hospitalisations, physician visits and medication use.

Again, using the example of IPF, in a recent analysis of healthcare costs and utilisation in patients covered by Medicare in the USA, it was estimated that the total annual medical costs in 2000–2011 were up to USD?3 billion, of which USD?1.8 billion was attributable to IPF and associated comorbidities.

Healthcare utilisation and costs of ILDs that may present a progressive fibrosing phenotype may be inferred from the similarities shared with IPF, but further studies are needed to clearly establish the burden and healthcare impact of this disease spectrum. Increased recognition of ILDs at risk of a progressive fibrosing phenotype should help advance our understanding.

The current therapeutic approaches utilised in patients with progressive-fibrosing ILDs are not well defined; however, antifibrotic therapies could demonstrate potential to address the unmet therapeutic need in these patients. Additional studies are required to further define this distinctive group of patients and to assess the impact of therapies, their effect on disease progression and subsequently on healthcare utilisation.