Idiopathic pulmonary fibrosis: Diagnosis, epidemiology and natural history.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing lung disorder of unknown aetiology whose diagnosis involves the careful exclusion of secondary causes for pulmonary fibrosis and the presence of a pattern of usual interstitial pneumonia (UIP) at either high-resolution computed tomography (HRCT) scan or surgical lung biopsy. Despite great efforts made in establishing precise, universally acknowledged diagnostic criteria for IPF, its ascertainment remains a challenge, especially in those individuals presenting with atypical HRCT patterns. With new drugs emerging, establishing a precise diagnosis is becoming a clinically relevant issue. Although regarded as a rare disease, IPF epidemiology is controversial due to studies relying on old data and adopting mixed, incomparable methodologies for cases definition. Overall, the prevalence and incidence appear to be increasing over the last decades, suggesting that in earlier studies they might have been underestimated because of diagnostic uncertainty. IPF is invariably progressive, although its clinical course might greatly vary on an individual basis, with episodes of severe acute respiratory deterioration (acute exacerbations) being unpredictable. A deeper understanding of the mechanisms responsible for an accelerated course of the disease and the identification of biomarkers of progression would lead to a better stratification of the disease, essential for delivering individualized therapeutic strategies.