A 70-year-old male, with a history of smoking presents with progressive dyspnea and dry cough. Examination reveals clubbing and fine basal crackles. Spirometry shows low forced vital capacity (FVC) and low diffusion capacity (DLCO). CT Chest shows extensive bilateral reticular shadows and subpleural honeycombing. What is the most likely diagnosis?
Idiopathic pulmonary fibrosis
Progressive dyspnea, dry cough, clubbing, fine bibasal crackles, a restrictive spirometry pattern (low FVC, low DLCO) and CT showing bilateral reticular shadows with subpleural honeycombing are the classic features of usual interstitial pneumonia pattern seen in Idiopathic Pulmonary Fibrosis. Sarcoidosis and COPD do not typically show honeycombing, and bronchiectasis shows a restrictive-obstructive picture with bronchial wall thickening rather than honeycombing.