Autoimmune Pulmonary Alveolar Proteinosis: A Rare Diagnosis in Pediatric Age

Autoimmune pulmonary alveolar proteinosis (AI-PAP) is a rare condition, especially in children. The clinical presentation ranges from asymptomatic forms to respiratory distress requiring ventilation. We describe the case of a 13-year-old adolescent male who presented to the emergency department with acute pleuritic chest pain not associated with systemic complaints. On examination, he had diminished breath sounds in the lower two thirds of the chest with no other abnormal findings; SpO₂ (oxygen saturation) was 98% on room air. Chest radiograph revealed a marked interstitial infiltrate, comparable with the one taken 4 years earlier during an acute illness that was presumptively treated with azithromycin. A computed tomography (CT) scan revealed multiple bilateral areas of ground-glass opacities with areas of crazy paving, involving > 65% of lung parenchyma, suggestive of pulmonary alveolar proteinosis (PAP). Respiratory viral testing, including for coronavirus (SARS-CoV2), was negative. Bronchoalveolar lavage performed in the outpatient setting revealed a milky fluid and positive periodic acid-Schiff staining. Spirometry indicated a mild restrictive pattern (forced vital capacity [FVC] = 77%) and diffusing capacity of the lungs for carbon monoxide (DLCO) showed a moderate decrease at 48.6%. No mutations associated with surfactant dysfunction were found on the genetic panel. Anti-granulocyte macrophage colony-stimulating factor (GM-CSF) antibody testing was strongly positive, raising suspicion for autoimmune PAP. At 20 months of follow-up, the patient remains asymptomatic with a normal spirometry. Although treatment with agents, such as the inhaled form of granulocyte-macrophage colony-stimulating factor (GM-CSF) appears promising for the treatment of symptomatic adult patients, as this patient remains asymptomatic, a conservative approach was taken, and he continues to be monitored in the clinic.