pulmonary alveolar microlithiasis (MONDO_0009928) is a disorder in which tiny fragments (microliths) of calcium phosphate gradually accumulate in the small air sacs (alveoli) of the lungs. These deposits eventually cause widespread damage to the alveoli and surrounding lung tissue (interstitial lung disease). People with this disorder may also develop a persistent cough and difficulty breathing (dyspnea), especially during physical exertion. Chest pain that worsens when coughing, sneezing, or taking deep breaths is another common feature. People with pulmonary alveolar microlithiasismay also develop calcium phosphate deposits in other organs and tissue of the body. Though the course of the disease can be variable,many casesslowly progress to lung fibrosis, respiratory failure, or cor pulmonale. The only effective therapy is lung transplantation. In some cases, pulmonary alveolar microlithiasis is caused by mutations in the SLC34A2 gene and inherited in an autosomal recessive manner.