Pleuroparenchymal fibroelastosis: Distinct pulmonary physiological features in nine patients

Background: Pleuroparenchymal fibroelastosis (PPFE) is a rare idiopathic interstitial pneumonia defined by pleural and subpleural parenchymal fibrosis predominantly in the upper lobes. Although the radiological and pathological characteristics of PPFE have become increasingly recognized, its pulmonary physiological features are not well understood. Methods: We reviewed nine patients with radiologically and histologically proven PPFE, and evaluated pulmonary physiological data. Results: Of the nine patients, six were male and three were female. The median age at presentation was 61 years. Common symptoms were dyspnea on exertion, weight loss, and nonproductive cough. Recurrent pneumothorax was found in eight patients and pneumonia in four. Median pulmonary function test results were as follows: forced vital capacity, 55.4% predicted; total lung capacity (TLC), 67.1% predicted; residual volume (RV), 102.3% predicted; and RV/TLC, 143.6% predicted. RV/TLC was increased without evidence of small airway disease according to clinico-radiologic-pathologic evaluation. The median partial pressure of oxygen in arterial blood and the alveolar-arterial gradient of oxygen were within normal limits, although there was a slightly elevated partial pressure of carbon dioxide in arterial blood (PaCO₂). PPFE progressed in all patients despite treatment with pirfenidone, corticosteroids, and immunosuppressive agents. Seven patients died during the follow-up, five because of hypercapnic respiratory failure. Conclusions: PPFE is characterized by severe mechanical restriction with high RV/TLC, causing increased PaCO₂ and eventual hypercapnic respiratory failure. These physiological findings may be useful as an adjunct in the diagnosis of PPFE.