Correct!
5. Small spherical, concentrically layered calcifications within alveoli
The patient described in this case was found to have pulmonary alveolar microlithiasis based upon his hallmark radiographic findings and surgical lung biopsy.
Pulmonary alveolar microlithiasis is a genetic disorder caused by one of several mutations in the gene that encodes the type IIb sodium phosphate cotransporter protein. This protein serve to transport free phosphate liberated during the breakdown of surfactant from the alveolar space into type II alveolar cells. When this protein is absent or dysfunctional, phosphate accumulates in the alveolar space. When a saturation point is reached with intraalveolar calcium, spherical calcium phosphate crystals (“microliths”) form. Mutations in the SCL34A2 are responsible for the disease, which is inherited in an autosomal recessive fashion and found with particular frequency in large consanguineous Middle Eastern families (3,4).
Key radiographic findings, discussed previously, include “sandstorm” pattern of microcalcifications, subpleural cyst formation (producing a “black pleural line”), and obscuration of the heart and mediastinal border by calcifications. Pulmonary physiology shows restrictive spirometry and poor diffusion capacity. There is often a marked discrepancy between the severity of the radiographic findings and clinical symptoms, and many cases are discovered incidentally. Pathology shows pathognomonic microliths, which are characterized by concentrically laminated spheres of calcium phosphate, typically about one micron in size.
There are no proven medical treatments for pulmonary alveolar microlithiasis, although corticosteroids and bisphosphonates have been used in an attempt to arrest further calcification. Successful single and bilateral lung transplantation has been reported and is the only definitive treatment known for pulmonary alveolar microlithiasis (5).
References