Pulmonary alveolar microlithiasis

DISCUSSION: Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive genetic disorder caused by mutations in the SLC34A2 gene which results in intra-alveolar accumulation of calcium phosphate microliths.

High resolution CT (HRCT) findings include:

• Diffuse sandstorm-like micronodules
• Interlobular septal thickening intermingled with areas of ground glass (crazy-paving pattern)
• Subpleural cysts
• Subpleural, peribronchial and septal calcifications
• Dense calcification outlining the mediastinal pleura and diaphragm
• Black pleural sign

Disease progression is variable; most patients remain asymptomatic despite radiological findings, while others experience progressive decline in pulmonary function. There is no current treatment for PAM; however, in advanced cases, lung transplant is considered.