Pulmonary Alveolar Microlithiasis - Clinico-Radiological dissociation - A case report with radiological review

Pulmonary alveolar microlithiasis (PAM) is a rare chronic lung disease characterized by deposition of intra alveolar calcium and phosphate in bilateral lung parenchyma with predominance in lower and mid zones. Etiology and pathogenesis is not fully understood. However, mutation in SLC34A2 gene that encodes a sodium phosphate co-transporter in alveolar type-II cells resulting in formation and accumulation of microliths rich in calcium phosphate due to impaired clearance is considered the cause of disease. Patients with PAM are asymptomatic till development of hypoxemia and cor pulmonale. It remains static, while in some it progresses to pulmonary fibrosis, respiratory failure and cor pulmonale. We report a case of 44 year old male patient presenting with progressive shortness of breath on exertion for one year in duration with dry cough, more since last six months. Chest radiograph showed dense micronodular opacities giving classical sandstorm appearance. High resolution computed tomography (HRCT) showed microcalcification, subpleural cystic changes and calcified pleura. Lung biopsy showed calcospherites within alveolar spaces.