Pulmonary alveolar proteinosis is a rare disease in which a type of protein builds up in the air sacs (alveoli) of the lungs, making breathing difficult.

In some cases, the cause of pulmonary alveolar proteinosis is unknown. In others, it is associated with infection or immune deficiency.

This rare disorder generally affects people 30 - 50 years old and is seen in men more often than in women.

• Cough
• Unintentional weight loss
• Fatigue
• Shortness of breath
• Fever

The doctor may hear crackles in the lungs. Often, the physical examination is normal.

Tests may reveal the following problems:

• Chest x-ray may show dense shadows similar to fluid build-up in the lungs (pulmonary edema).
• Arterial blood gases test may reveal low oxygen levels in the blood.
• Pulmonary function tests may show restrictive lung disease and abnormal diffusion.
• High-resolution CT scan of the chest may show dense infiltrates in both lungs.
• Bronchoscopy with saline wash of the lungs (lavage) may show a milky fluid.