Pulmonary alveolar proteinosis, unusual infiltrative lung disease, the dilemma for physicians: A case report and literature review

Introduction: Pulmonary alveolar proteinosis (PAP) is a diffuse pulmonary disease characterized by the intra-alveolar accumulation of formless, proteinaceous material. Lipids and proteins materials with specific staining appearance in the alveoli impair pulmonary gas transfer in PAP. The severity of this condition ranges from an asymptomatic clinical presentation to respiratory failure and death. PAP is an extremely rare disorder, occurring worldwide with an estimated prevalence of 0.1 per 100000 individuals. Although the pathogenesis of PAP has remained unknown, most investigators have considered this condition to be caused by the impaired clearance of lipids and surfactant proteins from the airspaces. These functions are known to be performed by alveolar macrophages and type 2 epithelial cells. It is likely that granulocyte macrophage-colony stimulating factor (GM-CSF) dysfunction on macrophages is responsible for PAP. Primarily, in most adult patients with PAP, antibodies against GM-CSF have been observed with dysfunction of macrophages. Secondly, alveolar macrophage dysfunction plays a role in the impaired secretion of surfactant in this disease. It has been noted that both impaired secretion of surfactant and impaired phagocytosis are responsible for disease pathogenesis. Case Report: A 40-year-old man who had suffered from a cough with sputum for more than 2 years, with no associated fever, referred to our clinic. He had been diagnosed with pneumonia and treated unsuccessfully with antibiotics. His past medical history showed that he had a chronic history of a cough, easy fatigability and shortness of breath upon mild exertion. Computed tomography (CT) imaging of the chest revealed bilateral diffuse reticulonodular opacities and a crazy-paving pattern, which was suggestive of alveolar proteinosis. Conclusion: PAP is a generalized pulmonary disorder caused by the collection of formless, proteinaceous material with specific staining appearance in the alveolus.