Pulmonary alveolar microlithiasis PAM is a rare disease caused by a mutation in the SLC34A2 gene encoding the type IIb sodium phosphate cotransporter in alveolar type II cells. ...Early in the disease, most patients are asymptomatic or might experience mild symptoms. However, in some patients, PAM can progress resulting in pulmonary fibrosis, cor pulmonale, and respiratory failure. ...