Pulmonary alveolar proteinosis (PAP) is a rare lung disorder. We herein report the first case of PAP that happened 2 years before myelodysplaticsyndrome (MDS). A 34-year-old Chinese presented with a developed recurrent cough and shortness of breath. Computed tomography scan disclosed ground-glass opacities with interlobular septal thickening. Histological examination showed eosinophilic dense homogenous material filling in the alveolar. This precipitate had a fine granular appearance. The eosinophilic material was periodic acid-Schiff reaction-positive. The patient was diagnosed with PAP. Two years later he was admitted to a hospital because of dizziness of 1-month duration. Hematological examination showed white blood cells was 2700, hemoglobin was 7.4 g/dL, and platelet count was 21,000 platelets/mm3. Following bone marrow biopsy and histopathologic examination, he was diagnosed with MDS with refractory anemia and excess blasts. So for PAP patients, follow-up tests should be considered in order to find any possible underlying disease.