Pulmonary Alveolar Proteinosis (PAP) is a rare lung disease characterized by the accumulation of a protein-rich substance in the alveoli, the tiny air sacs in the lungs. This buildup interferes with normal gas exchange, leading to symptoms such as shortness of breath, cough, and fatigue. PAP can be caused by various factors, including autoimmune diseases, exposure to certain chemicals, or may occur without a known cause. Diagnosis typically involves imaging tests like chest X-rays or CT scans, along with lung biopsies to analyze the fluid in the alveoli. Treatment options may include whole lung lavage, a procedure to wash out the excess protein, or medications to address underlying conditions.