Morphologic Aspects of Interstitial Pneumonia With Autoimmune Features

Abstract

Context.— Interstitial lung disease, a common complication observed in several connective tissue diseases, causes significant morbidity and mortality. Similar to individuals with connective tissue diseases, a significant subgroup of patients with clinical and serologic characteristics suggestive of autoimmunity but without confirmed specific connective tissue disease presents with associated interstitial lung disease. These patients have been classified using different controversial nomenclatures, such as undifferentiated connective tissue disease–associated interstitial lung disease, lung-dominant connective tissue disease, and autoimmune featured interstitial lung disease. The need for a better understanding and standardization of this entity, interstitial lung disease with autoimmune features, and the need for an adequate management protocol for patients resulted in the introduction of a new terminology in 2015: interstitial pneumonia with autoimmune features. This new classification requires a better comprehension of its diagnostic impact and the influence of its morphologic aspects on the prognosis of patients. Objective.— To review the diagnostic criteria for interstitial pneumonia with autoimmune features, with an emphasis on morphologic aspects. Data Sources.— The review is based on the available literature, and on pathologic, radiologic, and clinical experience. Conclusions.— The interstitial pneumonia with autoimmune features classification seems to identify a distinct subgroup of patients with different prognoses. Studies show that nonspecific interstitial pneumonia and usual interstitial pneumonia are the most prevalent morphologic patterns and show discrepant results on the impact of the usual interstitial pneumonia pattern on survival. Prospective investigations are necessary to better define this subgroup and to determine the prognosis and appropriate clinical management of these patients.

Interstitial Pneumonia with Autoimmune Features and Undifferentiated Connective Tissue Disease

“…Autoimmune disorders often affect more than one organ system. 12,41 Moreover, with known CTDs, multiple lung compartments (interstitium, pleura, airways, vasculature, or respiratory musculature) can be affected simultaneously. 12,15 Multicompartment involvement in the IPAF criteria refers to otherwise "unexplained" thoracic manifestations in the pleural, pericardial, airways of pulmonary vascular compartments identified through imaging, histopathology, right-heart catheterization, or pulmonary function tests.…”

“…12,41 Moreover, with known CTDs, multiple lung compartments (interstitium, pleura, airways, vasculature, or respiratory musculature) can be affected simultaneously. 12,15 Multicompartment involvement in the IPAF criteria refers to otherwise "unexplained" thoracic manifestations in the pleural, pericardial, airways of pulmonary vascular compartments identified through imaging, histopathology, right-heart catheterization, or pulmonary function tests. 15 Pulmonary hypertension (PH)-or its suggestion based on noninvasive studies rather than confirmatory right-heart catheterization-is a common finding among patients with IPAF, reported in as many as 53.6% of subjects in one study and 30.4% in another.…”

“…Results from some studies have shown that smoking is associated with increased mortality in IPAF, but this has not been a universal observation. 12,16,17 Multiple studies have shown increasing age to be an independent predictor of death. 12,17,38 Pulmonary physiology likely contributes prog-nostic information.…”

“…12,16,17 Multiple studies have shown increasing age to be an independent predictor of death. 12,17,38 Pulmonary physiology likely contributes prog-nostic information. 16 As highlighted above, a UIP pattern on HRCT or SLB may predict a worse prognosis than non-UIP patterns.…”

“…As with classifiable CTDs, a subgroup of patients with UCTD have concurrent ILD. [11][12][13] Such patients have been labeled with UCTD-ILD, lung-dominant CTD, autoimmune ILD, ILD with autoimmune characteristics, inappropriately as MCTD-ILD, and most recently, interstitial pneumonia with autoimmune features (IPAF). Unfortunately, besides the different names, investigators used differing case definitions in their studies, making the comparison or consolidation of results across studies invalid.…”