General Considerations

• Very rare, chronic disease characterized by widespread calcifications called "calcispherites" within the alveoli
• Etiology is unknown but it has a familial incidence with an autosomal recessive inheritance pattern
• No known calcium metabolism disorder
• Microliths range from 0.01 to 3 mm in size and are composed of calcium phosphate

Clinical Findings

• May remain asymptomatic until 3^rd-4^th decade
• First symptom is usually dyspnea on exertion
• Restrictive lung disease pattern
  • Eventually, there may be cyanosis and clubbing

Imaging Findings

• Diffuse, discrete, very small, symmetric micronodular calcifications (sand-storm appearance)
  • Predominantly in mid- to lower-lung zones with sparing of apices
• Heart borders and diaphragm are obliterated from view
• Denser subpleural layer
• "Black pleural line"
  • Increased lucency between dense lung parenchyma and ribs
• Small apical bullae
• High-resolution computed tomography is the study of choice
  • Diffuse ground-glass opacities
• May be more prominent centrally than peripherally
• Densely calcified, diffusely spread calcified nodules
• May show pleural calcification as well

Differential Diagnosis

• Same "crazy-paving" described with alveolar proteinosis may be seen in microlithiasis
• Silicosis
• Metastatic calcification in renal disease

Treatment

• None

Complications

• Respiratory insufficiency
• Cyanosis
• Clubbing
• Pulmonary hypertension

Prognosis

• Microliths may continue to form or disease may arrest

  

 

 

Pulmonary Alveolar Microlithiasis. Axial CT scans of the lower chest demonstrate extremely dense
calcific material at both lung bases (red arrows) which is also producing pleural calcification (black arrows). The
disease is seen to be composed of innumerable smaller calcifications (white circle). The black arrow on the conventional chest radiograph points to the lower lobe predominance. The blue arrow points to calcification of the fissures.
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