Clinical Pearls & Morning Reports
Published May 9, 2018
The most common idiopathic interstitial pneumonia is idiopathic pulmonary fibrosis (IPF), a chronic, progressive, fibrotic interstitial lung disease of unknown cause, often with characteristic imaging and histologic appearances, that occurs primarily in older adults. Read the latest NEJM Review Article here.
Q: What features of a patient’s presentation raise the possibility of interstitial lung disease?
A: Clinicians should consider interstitial lung disease in the differential diagnosis for adults presenting with unexplained exertional dyspnea, chronic dry cough, or Velcro-like crackles on examination. Spirometry should be performed and lung volumes and the diffusing capacity of the lung for carbon monoxide (DLco) should be measured in patients with suspected interstitial lung disease. These studies typically identify a reduced forced vital capacity (FVC), a reduced total lung capacity, and a reduction in DLco. Chest radiographs may be normal or show nonspecific findings in early disease. In more established disease, bilateral reticular infiltrates, hazy opacities, and reduced inspiratory lung volumes on chest radiographs should prompt consideration of interstitial lung disease.
Q: What are some of the conditions that mimic IPF?
A: Once interstitial lung disease has been identified on high-resolution computed tomographic (CT) studies, a focused history taking and physical examination should be performed to identify disorders that are known to cause interstitial lung disease, such as chronic hypersensitivity pneumonitis, or to be associated with it, such as connective-tissue disease, which are more common in younger and middle-age adults with interstitial lung disease. Patients can be questioned about exposure to dampness, mold, or birds in the home or workplace, which can cause chronic hypersensitivity pneumonitis. One can also look for signs and symptoms of autoimmune conditions, and test for antinuclear antibodies.
A: The findings on high-resolution CT can be used to infer whether the histologic pattern of IPF is present, thereby obviating the need for a lung biopsy in some cases. This pattern, termed “usual interstitial pneumonia” (UIP), consists of heterogeneous paraseptal fibrosis with architectural distortion. The term UIP is also used to describe a high-resolution CT pattern characterized by bilateral reticulation and honeycombing that is predominantly peripheral and in the lower lobes, which has a high positive predictive value for a histologic UIP pattern. Therefore, if no cause is identified, a typical UIP pattern on high-resolution CT is diagnostic of IPF. Atypical features on high-resolution CT, including upper-lung or midlung predominance, peribronchovascular predominance, subpleural sparing, predominant consolidation, extensive ground-glass opacities, extensive mosaic attenuation, and diffuse nodules or cysts, should raise suspicion of an interstitial lung disease other than IPF.
A: During the past 5 years, notable advances have been made in pharmacotherapeutic approaches to IPF. Two medications, nintedanib and pirfenidone, have been shown to be safe and effective in the treatment of IPF; both are recommended for use in patients with IPF. In placebo-controlled randomized trials, each drug has been shown to slow the rate of FVC decline by approximately 50% over the course of 1 year. Treatment guidelines for IPF include a strong recommendation against the use of prednisone in combination with azathioprine and oral N -acetylcysteine, a regimen associated with an increase in mortality by a factor of 9, as compared with placebo. Interferon-γ, endothelin antagonists, and warfarin are ineffective or harmful in patients with IPF. Although current guidelines recommend the use of antacid therapy to treat IPF, there are no data from clinical trials to support this recommendation.