Is It Idiopathic Pulmonary Fibrosis or Not?

Mary Salvatore, MD; Genta Ishikawa, MD; Maria Padilla, MD


J Am Board Fam Med. 2018;31(1):151-162. 

In This Article

Abstract and Introduction


Pulmonary fibrosis is not uncommon. Usual interstitial pneumonitis (UIP)/idiopathic pulmonary fibrosis (IPF) is the most common of the idiopathic pulmonary fibrotic diseases and has the worst prognosis with a mean life expectancy of 3.8 years. The American Thoracic Society has provided guidelines for the accurate diagnosis of IPF.

In 2014, 2 antifibrotic medications were approved in the United States that target the multiple fibrotic pathways of UIP, which increased the need for early and accurate diagnosis of IPF. The early and correct diagnosis is hampered by mimickers that include nonspecific interstitial pneumonitis, chronic hypersensitivity pneumonitis, and fibrotic sarcoidosis. Careful history taking, serologic testing, and Computer Tomography (CT) inspection can frequently make the correct diagnosis without need of invasive procedure. The purpose of this article is to share the most important aspects of the clinical and radiology presentation of IPF and its mimickers to enhance primary care clinician's ability to correctly and noninvasively diagnose UIP/IPF.


Fibrosis is the final common pathway of many injuries to the lung. Perhaps the earliest known cause of fibrosis was inhaled antigen-mediated hypersensitivity pneumonitis. In 1713, Bernadino Ramazzini recorded the health hazards associated with 52 occupations. He detailed the breathing difficulties related to maple-bark mold causing hypersensitivity pneumonitis.[1] In the early 1900s asbestos was touted as a fire-retardant material with excellent insulating capability. By the 1970s it was known to cause lung fibrosis and its usage was banned by the US Environmental Protection Agency. Radiation Fibrosis occurs in the lung when it is exposed to greater than 20 Gy of radiation.[2] Osteophytes of the spine can cause pulmonary fibrosis from mechanical irritation.[3]

In 1969 Liebow and Carrington[4] described a group of idiopathic interstitial pneumonias that included usual interstitial pneumonia (UIP) which is associated with the clinical diagnosis of idiopathic pulmonary fibrosis. The criteria for diagnosing UIP have been well established. Recently, the American Thoracic Society/European Respiratory Society provided an update of the Classification of Idiopathic Interstitial Pneumonias (IIPs). Four categories were defined: chronic-fibrosing IIPs, acute or subacute IIPs, smoking-related IIPs, and rare IIPs.[5] In clinical practice the fibrosing IIPs, which include usual interstitial pneumonitis (UIP) and fibrotic nonspecific interstitial pneumonitis (NSIP), are most frequently encountered and provide the greatest diagnostic dilemma because of their overlapping clinical, radiologic, and pathologic presentation. Chronic hypersensitivity pneumonitis (CHP) and fibrotic sarcoidosis (S4), which are not listed as idiopathic fibrosis, further complicate diagnosis because of their relative frequency and similar presenting features. The goal of this review article is to provide an overview of the clinical and radiologic diagnosis of UIP/idiopathic pulmonary fibrosis (IPF) and mimickers of the disease with the main goal being ability to answer the question, "Is it IPF or not?" Differentiation of fibrosis is important because treatments are different as well as prognosis. IPF is treated with antifibrotic medications, NSIP and S4 are often treated with anti-inflammatory medications, and CHP requires removal of the antigen causing disease. Early disease diagnosis leads to improved outcomes for patients.