Pulmonary Alveolar Proteinosis : Types, Risk Factors

Introduction 

Pulmonary Alveolar Proteinosis(PAP) is a very rare lung disease. This disease mainly involves the lung alveoli. There is an overproduction of lung surfactants in Pulmonary Alveolar Proteinosis(PAP). 

Types of Pulmonary Alveolar Proteinosis(PAP)

1. Congenital 
2. Secondary 
3. Autoimmune

Risk Factors of Pulmonary Alveolar Proteinosis(PAP)

• Smoking 
• Recurrent infections
• Unknown Etiology
• Autoimmune
  • PAP is the most common pathophysiologic mechanism, accounting for 90% of documented cases
• Inhalation of Environmental irritants

Epidemiology of Pulmonary Alveolar Proteinosis(PAP)

Pulmonary Alveolar Proteinosis(PAP) is a very rare disease. The most common cause of PAP is Autoimmune. It is seen more in males than females. The age group to be affected is the middle age group.

Pathophysiology Of Pulmonary Alveolar Proteinosis(PAP)

Type 2 Pneumocytes produce DPPC (Dipalmitoyl phosphatidylcholine) with Surfactant Proteins. GM-CSF (Granulocyte-Macrophage colony-stimulating factor) produced by alveolar macrophages clears the surfactant.

Clearance of surfactant decreased due to decreased bioactivity of GM-CSF and Accumulation of surfactant in alveoli.

This accumulation of surfactant causes pulmonary Fibrosis.

Also Read: IgG4 Related Disease: Histopathological Findings, Investigations

Causes of Pulmonary Alveolar Proteinosis(PAP)

• Congenital (Autosomal resistant)
• Acquired causes can be any of the following
  • Silicosis
  • Inhalation dust
  • Lysin uric acid intolerance
  • Hematological malignancies
  • Crystals of Quartz

Clinical Features of Pulmonary Alveolar Proteinosis(PAP)

• Dyspnoea on Exertion: when a person walks or does any work that requires effort.
• Fatigue: excessive tiredness and reduced energy 
• Weight loss: A person starts to lose weight as the breathing process is highly affected. 
• Fever: there is a low to moderate-grade fever present in the patients.
• Chunky gelatinous sputum plugs are also seen when the patient produces sputum.

Work Up of Pulmonary Alveolar Proteinosis(PAP)

• PFT (Pulmonary function tests): Restrictive pattern (FEV₁ / FVC is Normal or increased)
• Chest X-ray: The patient's chest X-ray film will show the snowstorm / "Bat wing" appearance of lung infiltrates.
• HRCT: “Crazy pavement" pattern (thickened interlobular septa)
• The investigation of choice is BAL (Bronchoalveolar lavage): Presence of PAS-positive lipo proteinaceous material
• PAS-positive is seen in:
  • Pulmonary alveolar proteinosis
  • Liver: ?₁ Antitrypsin deficiency
  • GIT: Whipple’s disease 

Management of Pulmonary Alveolar Proteinosis(PAP)

• Whole lung lavage

Frequently Asked Questions:

Q: What is the most common cause of Pulmonary Alveolar Proteinosis(PAP)?

Answer: Autoimmune

Q: Is it common to be affected by Pulmonary Alveolar Proteinosis(PAP)?

Answer: No, it is a very rare disease.

Q: The HRCT shows a “Crazy pavement" pattern. In which lung pathology is it?

Answer: Pulmonary Alveolar Proteinosis(PAP)

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