Pulmonary Alveolar Microlithiasis: A Unique Case of Familial PAM Complicated by Transplant Rejection.

Background: Pulmonary alveolar microlithiasis (PAM) is a rare lung disease characterized by the deposition of calcium phosphate microliths or calcospherites, within the alveolar airspace. Typical imaging findings demonstrate a "sandstorm" appearance due to bilateral, interstitial sand-like micronodularities with basal predominance.

Methods and results: We describe an unusual case of a 48-year-old male with severe, familial PAM ultimately treated with a bilateral lung transplant.

Conclusions: PAM is a rare lung disease caused by a mutation in the SLC34A2 gene, which encodes for a sodium-phosphate cotransporter in type II alveolar cells, leading to accumulation of intra-alveolar phosphate causing microlith formation. PAM has an indolent course but can progress to chronic hypoxic respiratory failure, ultimately requiring lung transplant, the only known effective treatment.