Pulmonary Alveolar Microlithiasis (PAM) is a rare disease of unknown origin. It is characterized by the presence of small calculi within the alveolar spaces, and has various clinical manifestations. Some patients may be asymptomatic for a long period of time with subsequent occurrence of dyspnea, dry cough, chest pain, and eventually, respiratory failure. Recurrent spontaneous pneumothorax episodes are a late complication of the disease. We report the case of an alveolar microlithiasis episode in a 42-year-old male, admitted to Tohid Hospital, Iran, whose first clinical presentation was symptoms of pneumothorax. He was admitted with sudden onset dyspnea and right-sided pleuretic chest pain. Following treatment of pneumothorax after chest tube placement, the pulmonary function revealed normal indices, and chest radiograph demonstrated diffuse confluence of dense micronodular infiltrate. High-resolution computerized tomography scan showed diffuse ground glass attenuation and calcifications along the interlobular septa and subpleural regions. Transbronchial lung biopsy confirmed the diagnosis of PAM.