Alveolar microlithiasis

Alveolar microlithiasis

Characteristics

  1. Very rare disease of unknown aetiology characterised by multiple tiny calculi deposited throughout the alveoli.
  1. 50% familial tendency.
  2. Equal sex incidence (M¼F).
  3. Often asymptomatic.
  4. Peak incidence between ages 30 and 50 years, but probably starts earlier in life.

Clinical features

  1. Majority have mild symptoms or are asymptomatic (70%).
  2. Disease progression is variable.
  3. Exertional dyspnoea is the commonest symptom and the majority of patients remain clinically stable throughout life following the onset of symptoms.
  4. Cyanosis and clubbing can occur. A minority develop pulmonary fibrosis and subsequent cor pulmonale.
  5. Normal serum calcium and phosphorus.

Radiological features

  1. CXR– multiple dense very fine sand-like micronodulations (<1 mm). The changes are diffuse and present throughout both lungs. Fibrosis can occur with further changes, including bullae most marked in thelung apices. Chronic cases may be associated with enlargement of the pulmonary arteries in keeping with secondary pulmonary hypertension.
  2. Bone scan – avid uptake of tracer throughout the lungs.

Differential diagnosis

  1. The main differential diagnosis lies between multiple healed calcified granulomata, particularly following a viral infection and inorganic pneumoconiosis, e.g. heavy metal inhalation. In practice the size of the nodules in these lesions coupled with the antecedent history should alert the clinician to the correct diagnosis.

Management

  1. No specific therapeutic options. Follow-up in symptomatic patients with assessment of pulmonary function in those who develop fibrosis and pulmonary insufficiency.
  2. No advantage to family screening in identified cases.

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