Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis is a rare lung disease in which surfactant-derived material accumulates inside alveoli and impairs gas exchange.

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Pulmonary surfactant: A lipid-and-protein mixture that lowers surface tension at the air–liquid interface lining alveoli. Surfactant-derived material is what accumulates in the alveoli in this disease.
Autoimmune pulmonary alveolar proteinosis: The most common form of pulmonary alveolar proteinosis, caused by autoantibodies that neutralize GM-CSF. This is the predominant disease subtype and explains most adult cases.
Bronchoalveolar lavage: A procedure that washes a selected lung region with sterile fluid and retrieves cells and material for analysis. Milky lavage fluid with characteristic material can support the diagnosis.
Crazy-paving pattern: A CT appearance combining ground-glass opacity with superimposed interlobular septal thickening. This imaging pattern is frequently associated with pulmonary alveolar proteinosis.
Alveolar macrophage: A resident immune cell that clears particles and surfactant from the lung’s air spaces. Impaired macrophage clearance is central to the most common autoimmune form.
Hereditary pulmonary alveolar proteinosis: Pulmonary alveolar proteinosis caused by inherited defects affecting GM-CSF signaling or surfactant production. Genetic forms can resemble autoimmune disease but arise through inherited defects.
Periodic acid–Schiff stain: A histochemical stain that highlights carbohydrate-rich substances in tissue and cells. PAS-positive material in lavage or biopsy specimens is a classic finding.
Pulmonary alveolar proteinosis in children: Pulmonary alveolar proteinosis presenting in childhood, often associated with genetic causes. Early onset raises suspicion for inherited disease rather than adult autoimmune disease.
Granulocyte-macrophage colony-stimulating factor: A cytokine that supports the development and function of myeloid cells, including alveolar macrophages. GM-CSF signaling enables macrophages to clear surfactant effectively.
Secondary pulmonary alveolar proteinosis: Pulmonary alveolar proteinosis associated with conditions that reduce the number or function of alveolar macrophages. This subtype links the same alveolar accumulation to an underlying disorder or exposure.