CASE 112

Contrast-enhanced chest CT (lung window, Figs. 112.1A, 112.1C, 112.1E; mediastinal window, Figs. 112.1B, 112.1D, 112.1F) demonstrates interlobular septal and fissural thickening and calcification, juxtapleural and pleural calcification, and profuse micronodular calcifications throughout both lungs. Note the preferential involvement of the peripheral secondary pulmonary lobule, producing sharply defined polygonal calcific opacities.

Diagnosis

Pulmonary Alveolar Microlithiasis (PAM)

Differential Diagnosis

• Amyloidosis (diffuse septal form)

• Granulomatous Infection

Miliary Tuberculosis

Disseminated Fungal Disease

• Sarcoidosis (micronodules more profuse in upper lobes; rarely calcify)

• Silicosis (micronodules more profuse in upper lobes)

• Talcosis (upper lobe nodules; aggregate into perihilar masses)

• Metastatic Ossification Chronic Renal Failure (calcifications larger; less well defined)

• Idiopathic Ossification (elderly men; calcifications not as pronounced)

Discussion

Background

Pulmonary alveolar microlithiasis (PAM) is a rare disorder characterized by accumulation of calcium phosphate calcospherites within the alveolar spaces.

Etiology

The etiology is unknown. A familial occurrence (autosomal recessive) has been noted in approximately 50% of reported cases.

Clinical Findings

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