Pulmonary Alveolar Proteinosis: An Overview and Emerging Therapeutics

Pulmonary alveolar proteinosis (PAP) is a rare pulmonary syndrome characterized by surfactant accumulation in the alveoli, which results in impaired gas exchange. There are three types of PAP: primary, secondary and congenital. Autoimmune PAP, which is under the category of primary PAP, is the most common form, and is caused by an impairment in granulocyte–macrophage colony-stimulating factor (GM-CSF) signalling, due to the presence of anti-GM-CSF autoantibodies. While some patients with PAP remain asymptomatic, most present with progressive dyspnoea of insidious onset that, rarely, can progress to respiratory failure and death. Currently, there is no known cure and no approved therapies for PAP. Whole-lung lavage remains the gold-standard treatment; however, several novel and promising targeted therapies are being actively investigated.