A 60-year-old man presented with an 18-month history of gradually worsening cough and a 12-month history of dyspnea on exertion. High-resolution computed tomography showed bilateral uniform ground grass opacity in the lower lung fields, partially resolved by smoking cessation. A tentative diagnosis of desquamative interstitial pneumonia (DIP) was made. Video-assisted thoracic surgery was performed and pathological analysis showed peribronchiolar fibrosis with intra-alveolar macrophage infiltration. Elemental analysis detected aluminum and iron in the upper lobe and only iron in the lower lobe. Thus, a definitive diagnosis of mixed dust pneumoconiosis with DIP-like reaction was made. DIP-like reaction is known to be a reactive change caused by exposure to tobacco smoke as well as by inhalation of inorganic particles. Obtaining a detailed medical history including occupational and environmental risk factors is important to distinguish cases of DIP-like reaction due to exposure to inorganic particles from the usual cases related to smoking, and thus provide suitable treatment. (C) 2017 Jichi medical university. Published by Elsevier Ltd. This is an open access article under the CC-BY-NC-ND license.