Classification and Natural History of the Idiopathic Interstitial Pneumonias

Abstract

In the American Thoracic Society/European Respiratory Society consensus classification, idiopathic interstitial pneumonias are classified into seven clinicopathologic entities. The classification is largely based on histopathology, but depends on the close interaction of clinician, radiologist, and pathologist. An accurate diagnosis can be very difficult, especially when deciding between idiopathic pulmonary fibrosis and fibrotic nonspecific interstitial pneumonia; better diagnostic markers are needed. The prognosis of idiopathic pulmonary fibrosis is very poor, with median survival of 2-4 yr after the diagnosis, yet the course of individual patients is highly variable. Predicting prognosis in the individual patient is challenging but various clinical and radiologic variables have been identified. According to several recent clinical trials, the natural history of this disease may involve periods of relative stability punctuated by acute exacerbations of disease that result in substantial morbidity or death. Nonspecific interstitial pneumonia is characterized by a distinct histopathologic appearance and a better prognosis than idiopathic pulmonary fibrosis. However, there is still confusion and controversy over the relationship between idiopathic pulmonary fibrosis and fibrotic nonspecific interstitial pneumonia.

Long‐Term Outcome and Use of 6‐Minute Walk Test in West Highland White Terriers with Idiopathic Pulmonary Fibrosis

“…This finding is in line with human IPF, where DAD is reported as a common terminal histopathologic finding related to AEs 6. Human IPF patients with AEs have a very poor prognosis despite treatment efforts 5, 6.…”

“…The median survival of WHWTs with IPF has been reported in a retrospective study to be 16 months from onset of clinical signs and 7 months from diagnosis, but speculated not to shorten life expectancy as the disease affects middle‐aged to older WHWTs 2. In humans, median survival of IPF patients from diagnosis is only 2–3 years,5 whereas fibrotic NSIP has a better prognosis of 6–13.5 years 6, 7…”

“…Several factors have been associated with poor survival in humans, including decreased walking distance in 6‐minute walk test (6MWT),8 increasing grade of interstitial fibrosis on thoracic radiographs,9 fibrosis score and traction bronchiectasis in thin‐section computed tomography,10 increased bronchoalveolar lavage (BAL) neutrophilia,11 and presence of pulmonary hypertension 12. In human IPF with a step‐like progression, periods of relative stability are interrupted by acute exacerbations (AEs), which are associated with high mortality and a histopathologic pattern of diffuse alveolar damage (DAD) 6. In WHWTs with IPF, DAD has been demonstrated along with consequent organizing luminal fibrosis, suggesting a more rapid progression of the fibrosis through organizing DAD in some dogs 4…”

The bleomycin animal model: A useful tool to investigate treatment options for idiopathic pulmonary fibrosis?

“…Mortality during acute exacerbation is high. The prevalence of IPF is estimated at 20/100,000 for males and 13/100,000 for females, and survival time from diagnosis ranges from 2 to 4 years (D. S. Kim, Collard, & King, 2006). Histological characteristics of UIP include remodeling of lung architecture with fibroblastic foci and "honeycombing".…”

Validation of the COPD Assessment Test (CAT) in patients with idiopathic pulmonary fibrosis

“…It accounts for approximately 55% of all new cases [2,3]. It is characterized by fibrotic scarring in the lung tissue subsequent to lung injury that remains poorly understood [1].…”