Usual interstitial pneumonia: a pattern or a disease? A reflection upon the topic

There are many ways in which a set of biological variables (clinical, laboratory, or histological variables) can characterize a distinct disease. In modern medicine, a nosological entity is most commonly determined by the primary factor responsible for the disease. Nevertheless, when the etiologic factor is unknown, a syndromic approach is the surrogate approach for establishing a diagnosis. The Brazilian Thoracic Association Guidelines for Interstitial Lung Diseases (1) have recently been published. In conformity with the official 2011 American Thoracic Society Statement, idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, occurring primarily in older adults, being limited to the lungs, and being associated with the histopathological/ radiological pattern of usual interstitial pneumonia (UIP), the diagnosis of IPF requiring the exclusion of other forms of interstitial pneumonia. It is a syndromic approach to diagnosis, given that the essential etiologic factor remains unknown. Typically, guidelines on a given subject gather the most relevant information available at the time, providing an excellent opportunity for a critical analysis of the subject in question. In this context, we would like to spark off a debate by asking the following question: would UIP be considered a disease in its own right if the accumulated evidence were viewed in a different light? Because UIP has such a peculiar histological pattern, chest HRCT is able to predict the histological features of UIP with a great degree of confidence in some typical cases, dispensing with a biopsy. The uniqueness of UIP is determined by the process of fibrosis formation (peripheral, with temporal and spatial heterogeneity, and minimal inflammation). It is a maladaptive repair process regardless of whether it is idiopathic or related to other diseases. This unique fibrotic process is designated IPF when it is not associated with other diseases. However, from a nosological point of view, the real difference between UIP related to other conditions (such as collagen vascular diseases and hypersensitivity pneumonitis) and its " idiopathic " form is unclear. We should now turn back to our initial considerations. When proposing that UIP be considered a disease in its own right, we took into consideration the characteristics that define a nosological entity. The histological features of UIP are distinctive enough to characterize a disease: • BLOCKINA disease of the lung repair process, UIP results in a peculiar form of fibrotic deposition, regardless of its relationship with other …