🫁 Pulmonary Alveolar Proteinosis (PAP) is a rare but potentially treatable lung disorder, presenting with dyspnoea, cyanosis, and finger clubbing. It results from impaired surfactant clearance, leading to alveolar filling with protein-rich material.

📖 About

Extremely rare interstitial lung disease.
Potentially reversible with correct treatment (e.g., whole-lung lavage).

⚙️ Aetiology & Pathogenesis

Failure of alveolar macrophages to clear surfactant → accumulation of proteinaceous material in alveoli.
Often related to defective or blocked GM-CSF (granulocyte-macrophage colony-stimulating factor) signalling.

⚠️ Risk Factors

🚬 More common in smokers.
🌫️ Exposure to dusts, fumes, or environmental toxins (esp. in secondary forms).

📂 Classification

Primary (Idiopathic) – most common; autoimmune (anti–GM-CSF antibodies often present).
Secondary – due to underlying disease (e.g., leukaemia, lung cancer, chronic infections, toxic exposures).
Congenital – very rare, due to genetic defects in surfactant protein or GM-CSF receptor.

🩺 Clinical Features

Progressive exertional breathlessness 🫁.
Fatigue, weight loss, low-grade fever.
Fine inspiratory crackles and finger clubbing ✋.
Cyanosis in advanced disease 🔵.

🔍 Investigations

🧪 LDH: typically elevated.
📸 CXR: bilateral diffuse alveolar shadowing.
🖼️ HRCT: “crazy-paving” pattern (ground-glass + septal thickening).
💉 BAL: milky fluid, foamy macrophages, PAS-positive material.
🧬 Lung biopsy: alveoli filled with PAS-positive granular material, architecture preserved.
🧪 Anti–GM-CSF antibodies: present in primary PAP.

💊 Management

👀 Observation if mild/asymptomatic.
🚿 Whole-lung lavage – gold standard treatment; significantly improves oxygenation.
💉 Exogenous GM-CSF therapy (inhaled or subcutaneous) in autoimmune PAP.
🚭 Smoking cessation essential.
🦠 Monitor for opportunistic infections (can complicate PAP course).

📚 References

Pulmonary Alveolar Proteinosis – Khan & Agarwal, Respiratory Care Journal

Cases — Pulmonary Alveolar Proteinosis (PAP)

Case 1 — Classic presentation 🌫️: A 34-year-old man presents with 6 months of progressive dyspnoea and dry cough. Exam: fine inspiratory crackles, mild clubbing. CXR: bilateral perihilar “bat-wing” opacities. HRCT: crazy-paving pattern. BAL fluid: milky and PAS-positive. Diagnosis: autoimmune PAP. Managed with whole-lung lavage and GM-CSF therapy.
Case 2 — Secondary PAP (occupational) ⚒️: A 42-year-old sandblaster reports progressive exertional breathlessness and fatigue. He has no autoimmune history. HRCT shows ground-glass opacities with interlobular septal thickening. BAL confirms proteinaceous material. Diagnosis: secondary PAP due to silica exposure. Managed with removal from exposure and supportive therapy.
Case 3 — Severe hypoxaemia 🫁: A 28-year-old man presents with acute worsening breathlessness, PaO₂ 6.8 kPa on air. He is hypoxic despite high-flow oxygen. HRCT: extensive crazy-paving pattern. Urgent BAL confirms PAP. Diagnosis: severe pulmonary alveolar proteinosis with respiratory failure. Managed in ITU with serial whole-lung lavage and rescue GM-CSF therapy.

Teaching Point 🩺: Pulmonary alveolar proteinosis is a rare disorder where surfactant accumulates in alveoli due to defective clearance by alveolar macrophages. Presents with progressive dyspnoea and “crazy-paving” on HRCT. Causes: autoimmune (anti-GM-CSF), secondary (dust exposure, haematological malignancy), congenital. Treatment is usually whole-lung lavage ± GM-CSF.

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Pulmonary Alveolar Proteinosis