Pulmonary Alveolar Proteinosis. Case-report Pulmonary alveolar proteinosis is a rare pathology in children, characterized by the presence of lipoprotein material becoming from surfactants in alveolar macrophages. Objetive: Describe a clinical case of pulmonary proteinosis, in which fibrobronchoscopy (FB) allowed diagnosis and treatment. Case-report: A 7 years-old boy with fever and diagnostic presumption of pneumonia. The evolution was not favorable, in terms of increase in nodular images on chest X-ray and increase in LDH plasmatic level, with few respiratory symptoms. The diagnosis of pulmonary alveolar proteinosis was suspected, performing a FB with bronchoalveolar lavage, where Sudán and PAS colouring confirmed the diagnosis. Discussion: Analysis of clinical presentations, laboratory findings and chest images that suggest the diagnosis. It is important to point out the role of FB in diagnosis and treatment