ABSTRACT
Interstitial lung diseases (ILDs) are a heterogenous group of over 300 diseases with a limited repertoire of treatment options. Diagnosis can present a considerable challenge to the clinician. ILDs can be classified into disorders of known cause, granulomatous diseases, other causes and idiopathic interstitial pneumonias (IIPs) (Figure 7.1), with the latter group updated in 2013 to include major, minor IIPs and unclassifiable disease (Table 7.1) (1,2). Classifications can be justified for a number of reasons including the identification of important distinctions in the natural history and treated course. This applies to the IIP classification, which consists of the definition of clinical entities built on histopathologic and high-resolution computed tomography (HRCT) features. The IIP classification can be used as a template for the formulation of an optimal management plan. By contrast, an aetiologic classification of ILD is useful for diseases that are managed by removing the underlying cause or treating the underlying cause directly. However, it does not discriminate between important idiopathic ILD entities and fails to address emergent phenotypes that are diagnostically challenging (3).
