Fibrotic lung diseases on HRCT: imaging and differential diagnosis

Interstitial lung diseases (ILDs) represent a heterogeneous group of entities, some of them characterized by an excessive deposition of extracellular matrix, in particular collagen, associated with a progressive destruction of the lung parenchyma. Thig group of diseases includes both idiopathic and secondary conditions. Although the underlying causes are different, some fibrotic lung diseases show a similar chronic progressive behavior, independently of the underlying etiology. An accurate diagnosis is mandatory to guide management and treatment of patients with interstitial lung diseases, in particular those with a fibrotic pattern. Imaging, and in particular high-resolution CT, plays a central role, therefore it is fundamental that radiologists become familiar with these diseases and their presentations, in order to be able to provide one or a limited number of possible differential diagnosis.