Pulmonary Alveolar Microlithiasis
Definition
- Autosomal recessive lung disease characterized by filling of alveoli by calcospherites
Diagnostic Criteria
- Clinical
- Autosomal recessive
- Caused by mutations in SLC34A2 sodium dependent phosphate transporter
- Normally expressed by type II alveolar macrophages
- Caused by mutations in SLC34A2 sodium dependent phosphate transporter
- Gradual onset and progression
- About half of patients are found upon screening families of patients
- Most are asymptomatic, even if the deposition is extensive
- Average age of clinical presentation around 30
- Can be found in infants
- May take decades to progress to respiratory failure
- No effective treatment except lung transplant
- Autosomal recessive
- Radiology
- Chest x-ray
- “Sand storm” of calcified densities
- Mainly lower and mid zones
- High resolution computed tomography (HRCT)
- Thickening and calcification of pleura, interlobular septa, bronchovascular bundles
- Focal ground glass opacities and consolidation
- Subpleural cysts
- Chest x-ray
- Histopathology
- The diagnosis can usually be made without a biopsy based on history and radiology
- Bronchoalveolar lavage and sputum may demonstrate microliths
- Biopsy shows diffuse filling of alveolar air spaces by calcospherites
- 250-750 microns but may reach 3 mm
- Lamellated calcifications
- Principally composed of calcium and phosphate
- Late stages may show increased localization to subpleural, paraseptal and peri-bronchovascular regions
- Fibrosis and ossification may occur in same areas
- The diagnosis can usually be made without a biopsy based on history and radiology
Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
