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Pulmonary alveolar proteinosis (PAP) is an under-reported and under-diagnosed condition, with a high percentage of cases found on autopsy or late stage disease. The etiology of PAP includes genetic, primary (anti-granulocyte-macrophage colony-stimulating factor antibodies) and secondary (oncologic, rheumatologic, infectious, chemical and immunologic) causes. Here, we present the first reported pediatric case of endogenous lipoid pneumonia and non-specific interstitial pneumonitis preceding the development of PAP., (© 2014 John Wiley & Sons Ltd.)

We report a unique case of coexisting exogenous lipoid pneumonia, endogenous lipoid pneumonia (ELP), and pulmonary alveolar proteinosis (PAP) in a 5-year-old patient with severe neurodevelopmental disease. The patient presented with gastroesophageal reflux and presumed chronic lung disease resulting from recurrent aspiration pneumonias and succumbed to respiratory failure. The autopsy showed lipid-laden macrophages and periodic acid-Schiff-positive granular material in alveolar spaces and multilamellated structures within both alveolar macrophages and extracellular debris. These findings were similar to those in previous reports of coexisting ELP and PAP in the setting of gastroesophageal reflux. However, the present case differed by the presence of scattered large osmiophilic extracellular lipid vacuoles. Besides strengthening the association between ELP and PAP and their relationship to gastroesophageal reflux, this case suggests that they may arise together with exogenous lipoid pneumonia, through related mechanisms, in the setting of neurodevelopmental disease.

Benign pulmonary diseases that have been associated with the accumulation of endogenous lipids within the alveoli, bronchioles, and interstitial tissues include endogenous lipoid pneumonia (ELP), pulmonary alveolar proteinosis (PAP), pulmonary interstitial and intra-alveolar cholesterol granulomas (PICG), various xanthomatous lesions, and malakoplakia. In ELP, fat-filled finely vacuolated macrophages fill the alveoli. In PAP, the aveoli become filled with cholesterol and periodic acid-Schiff (PAS)-positive acellular debris. In PICG, cholesterol esters are released from degenerating macrophages and, as organization occurs, the cholesterol is deposited in the form of acicular clefts within the interstitium. These morphologically distinct presentations of endogenous lipid deposition within the lung have long been thought to represent unique disease processes but several authors now postulate a possible relationship between these entities. We report here on the clinical, radiographic, and morphologic findings in eight pediatric patients with diverse primary disease processes who were subsequently found to have varying and often coexisting degrees of ELP, PAP, and PICG.