Underlying disease of secondary pulmonary alveolar proteinosis

• Secondary alveolar proteinosis is thought to be caused by a decline in the cleaning ability of alveolar macrophages, which clean the inside of the alveoli.
• The most common cause is secondary to blood disorders, but it is also caused by infectious diseases and collagen diseases, such as Behcet's disease.
• Among blood diseases, myelodysplastic syndrome accounts for 70% of cases.
• Compared to reports from Europe and the United States, Japan is unique in that the rate of secondary pulmonary alveolar proteinosis associated with myelodysplastic syndrome is high.