TYPE: Abstract Publication TOPIC: Diffuse Lung Disease PURPOSE: Pleuroparenchymal fibroelastosis (PPFE) is increasingly being recognized as a distinct clinical entity. We present a case of a young male with dyspnea and functional impairing. METHODS: Case report RESULTS: Male, 30 years-old, with progressive dyspnea mMRC 3 and dry cough. Light smoker, 5 pack-years, with familial history of interstitial disease and lung transplant. Chest-CT revealed bilateral subpleural opacities and pleural thickening restricted to the upper lobes, without lymph node enlargement. Functional evaluation showed restrictive ventilatory defect (FVC 37%, FEV1 40,9%, I. Tiff. 93, TLC 44,7%), low DLCO (43,1%) and desaturation to 74% in 6 minute walk test. Normal blood analysis, including autoimmunity and SACE. Bronchoalveolar lavage with macrophage predominance, CD4/CD8 ratio 1,3 and positive Ziehl–Neelsen in citology. Patient was treated with isoniazid, rifampicin, pyrazinamide and ethambutol for 2 months followed by maintenance treatment, with some clinical improvement, but persistence of radiological and functional abnormalities. CT-guided transthoracic lung biopsy (TTLB) was inconclusive due to mostly pleural representation. Iatrogenic pneumothorax occurred with need of drainage. A second TTLB was performed revealing fibrosis and elastosis of lung parenchyma, without granulomas or honeycombing. CONCLUSIONS: The symptoms, radiologic and histologic findings are compatible with PPFE. However, differential diagnosis includes other diseases with upper lobe predominance, like sarcoidosis and tuberculosis. The latter may occur due to increased susceptibility of these patients to opportunistic infections. CLINICAL IMPLICATIONS: To make an accurate diagnosis in diffuse lung diseases a multidisciplinary approach is needed. A continuous update is important to warrant the correct recognition and classification of diseases. DISCLOSURE: No significant relationships. KEYWORDS: Pleuroparenchymal fibroelastosis, Diffuse lung diseases, Multidisciplinar