Pulmonary Alveolar Proteinosis

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Pulmonary Alveolar Proteinosis is a rare cause of cyanosis and finger clubbing.

About

• It is a rare lung disorder
• It is a potentially treatable disease

Aetiology

• Impaired processing of surfactant which accumulates in the alveoli of proteinaceous material rich in surfactant protein and its component
• Defective GM-CSF signalling

Risk factors

• Commoner in smokers

Aetiology

• Abnormal accumulation of surfactant -derived lipoprotein compounds within the alveoli of the lung.

Classification

• Primary PAP : most typical and the most common form.
• Secondary PAP : possible to identify a specific factor that actually caused the condition, such as leukaemia or lung cancer, dust or fume inhalation, infections
• Congenital PAP:extremely rare and is caused by a genetic disorder

Clinical

• Presents with progressive dyspnoea on exertion
• Progressive fatigue, weight loss, and low-grade fever
• Fine end-inspiratory crackles and clubbing are seen
• Very rarely cyanosis and clubbing

Investigations

• Serum lactate dehydrogenase (LDH) level is usually elevated
• CXR - bilateral alveolar shadowing
• HRCT scan - ground glass appearance, Crazy-paving appearance in a geographic distribution is a characteristic feature of this disease visible
• Bronchoalveolar lavage - large foamy macrophages and a milky appearance
• Lung biopsy: typically shows partial or complete filling of alveoli with periodic-acid-Schiff-positive granular and eosinophilic material in preserved alveolar architecture
• Analysis shows PAS +ve staining
• Antibodies to granulocyte-macrophage colony-stimulating factor are found

Management

• Patients with minimal symptoms are managed conservatively, whereas patients with hypoxemia require a more aggressive approach.
• Whole-lung lavage is the most widely accepted therapy for symptomatic pulmonary alveolar proteinosis. It most often results in a dramatic response.
• Correction of GM-CSF deficiency with exogenous GM-CSF is an alternative therapy
• Smoking cessation is important. Most resolve. Superinfection can occur.

References

• Pulmonary Alveolar Proteinosis. Ajmal Khan MD DM and Ritesh Agarwal MD DM