 This cross sectional study protocol is designed to evaluate the autoimmune aspect of PAP in patients that are currently being followed by clinical investigators in the Rare Lung Disease Consortium RLDC. The study involves a retrospective chart review and serological analysis of preexisting, stored serum samples from individuals diagnosed with PAP. Thus, this study will not involve any direct interactions or contact with PAP patients or any other study participants. It will yield diagnostic information regarding the use of anti-granulocyte macrophage-colony stimulating factor GM-CSF autoantibody testing in patients with PAP. It will also yield information about the extent of the autoimmune response in primary PAP. In addition, the study will comparecontrast the clinical phenotypes of individuals with anti-GM-CSF autoantibody-positive PAP in various regions of the world. A stringent evaluation of the autoimmune aspects of PAP including rigorous anti-GM-CSF antibody testing will provide a better understanding of PAP and is expected to confirm the usefulness of serum anti-GM-CSF antibody testing in the clinical diagnosis of PAP. The study will evaluate the rate of serious or opportunistic infections and other clinical and demographic data from patients in various regions of the world to determine if significant differences exist, which will provide important knowledge regarding infectious and other complications associated with PAP. 