Pulmonary Alveolar Microlithiasis

Epidemiology

  • Incidence: rare disorder
  • Familial Clustering: present in >50% of cases
    • Especially clusters in siblings
  • Age: most cases are diagnosed in 20’s-40’s
    • Has been reported in all age groups though
  • Sex
    • Female>male in familial cases
    • Female=male in sporadic cases

Physiology

  • Accumulation of hydroxyapatite (calcium and phosphorous) crystal concretions (0.01-3 mm) in alveolar spaces (probably due to some inborn error of caclium metabolism)
  • Over time, alveolar walls become fibrotic

Diagnosis

  • CXR/Chest CT Pattern
    • Early: characteristic diffuse bilateral calcific alveolar infiltrates (with air bronchograms) with lower lobe predominance
      • “Vanishing heart phenomena”: due to microliths adjacent to heart border
      • “Black and white” pleural-related lines (pathognomonic): white thick line at subpleural area adjacent to black pleural line (a Mach band)
      • Chest CT: lower lobe and subpleural predominance of intra-alveolar calcified nodules, pleural calcifications may be seen
    • Later: ILD, evidence of pulmonary hypertension
  • PFT’s: usually normal until late in course, when restriction with decreased DLCO occurs
  • FOB: TBB may aid in confirming diagnosis
  • Bone Scan: may aid in confirming diagnosis
  • Serum Calcium and Phosphorous: normal
  • CBC: polycythemia (occurs late in course, associated with hypoxemia)

Clinical

(may be asymptomatic even with extensive CXR abnormalities)

  • Interstitial Lung Disease (see [[ILD-Etiology]])
    • Clubbing
    • Cough and dyspnea: occur late in course
    • Expectorated Microliths: occurs infrequently
    • Crackles: occur with later development of ILD
  • Cor Pulmonale (see [[Pulmonary HTN-Etiology]])

Treatment

  • Supportive treatment:
  • Whole Lung Lavage: not useful

Prognosis

  • Progression is variable

References

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