# Pulmonary Alveolar Proteinosis

> Pulmonary alveolar proteinosis for NEET-PG Medicine: crazy-paving HRCT, anti-GM-CSF autoantibodies, secondary causes, lavage and steroid avoidance.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/pulmonary-alveolar-proteinosis
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Harrison's Principles of Internal Medicine; Murray and Nadel's Textbook of Respiratory Medicine; Davidson's Principles and Practice of Medicine
- How to cite: "Pulmonary Alveolar Proteinosis", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/pulmonary-alveolar-proteinosis

## Direct answer

Pulmonary alveolar proteinosis is a rare disorder in which surfactant-derived lipoproteinaceous material accumulates within the alveoli, and most adult cases are autoimmune, caused by neutralising antibodies against granulocyte-macrophage colony-stimulating factor. HRCT typically shows bilateral ground-glass opacities with superimposed interlobular septal thickening, the crazy-paving pattern. Whole-lung lavage is the definitive treatment for symptomatic patients, while inhaled GM-CSF is an emerging option in selected cases.

## What you must remember

- **Autoimmune disease:** anti-GM-CSF autoantibodies impair alveolar macrophage clearance of surfactant and account for most adult cases.
- **Secondary forms:** haematological malignancy, silica or aluminium dust exposure and severe infections, notably Nocardia and mycobacterial disease, can produce the same picture.
- **Crazy-paving pattern:** ground-glass opacities with septal thickening; the differential includes Pneumocystis pneumonia, pulmonary oedema and alveolar haemorrhage.
- **BAL fluid:** milky appearance with periodic acid-Schiff positive granular material, which is both diagnostic and therapeutic.
- **Whole-lung lavage:** performed under general anaesthesia with a double-lumen tube, one lung at a time, with warm saline.
- **Infection risk:** nocardiosis, aspergillosis and mycobacterial disease are common complications and should be excluded before lavage or immunosuppression.
- **Steroids:** corticosteroids are not effective in alveolar proteinosis and may increase opportunistic infection.

## A diagnostic route for a breathless adult

A 38-year-old man with eight months of progressive exertional breathlessness and a saturation of 91 percent on room air shows the workup in order.

1. **Image the chest:** HRCT shows bilateral crazy-paving, which is suggestive but not specific.
2. **Sample the alveoli:** Bronchoscopy with lavage returns milky fluid rich in periodic acid-Schiff positive material.
3. **Screen for secondary causes:** Before accepting the diagnosis, a full blood count and LDH exclude haematological malignancy, a detailed occupational history checks for silica exposure, and immunosuppression that might explain opportunistic infection is looked for.
4. **Confirm autoimmunity:** Serum anti-GM-CSF testing, available in specialist centres, confirms an autoimmune basis.
5. **Plan lavage safely:** Because he is symptomatic and hypoxic, whole-lung lavage is planned after infection screening, and corticosteroids are withheld.
6. **Track the response:** Follow-up tracks saturation and symptoms, and repeat lavage is considered if breathlessness or the oxygen requirement worsens again. Inhaled granulocyte-macrophage colony-stimulating factor is discussed in specialist centres where it is available.

## Where the exam tries to catch you

Examiners return to a few traps in alveolar proteinosis questions.

- **Trap:** Treating crazy-paving on HRCT as the diagnosis. — **Correct:** Crazy-paving is a pattern, not a diagnosis, and bronchoalveolar lavage or biopsy is what confirms alveolar proteinosis.
- **Trap:** Giving steroids because the picture resembles interstitial disease. — **Correct:** Steroids seem logical for interstitial disease but are wrong here and risk opportunistic infection.
- **Trap:** Stopping at an autoimmune label in a stem with lymphoma or silica exposure. — **Correct:** The answer turns to the underlying cause rather than an autoantibody.

In an Indian context, stone quarrying and silica exposure are common occupational settings, so a silica history should prompt a search for both silicosis and secondary proteinosis.

## Frequently asked questions

### What HRCT pattern is characteristic of pulmonary alveolar proteinosis?

The crazy-paving pattern on HRCT is characteristic of pulmonary alveolar proteinosis, showing ground-glass opacities with superimposed interlobular septal thickening. The pattern is not specific, so bronchoalveolar lavage or biopsy is needed to confirm the diagnosis.

### What is the autoantibody in autoimmune pulmonary alveolar proteinosis?

Neutralising autoantibodies against granulocyte-macrophage colony-stimulating factor, abbreviated anti-GM-CSF, cause most adult pulmonary alveolar proteinosis. They impair alveolar macrophage clearance of surfactant, leading to progressive alveolar filling.

### Why is whole-lung lavage used in pulmonary alveolar proteinosis?

Whole-lung lavage physically removes the accumulated proteinaceous material from the alveoli and is the definitive treatment for symptomatic disease. It is performed under general anaesthesia with a double-lumen tube, treating one lung at a time.

### Why should corticosteroids be avoided in pulmonary alveolar proteinosis?

Corticosteroids are not effective in alveolar proteinosis and may increase the risk of opportunistic infections, which are already a major complication. Infection, including nocardiosis and mycobacterial disease, should be excluded before any immunosuppression.