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Pulmonary alveolar microlithiasis (PAM) is a rare, autosomal recessive lung disease associated with accumulation of calcium phosphate microliths in the alveolar space. #1 Epidemiology in Japan PAM is found worldwide, but it predominates in a few countries, particularly Japan, Turkey and Italy. However, it is unknown whether this accurately reflects the distribution of the patients in the world. The Japanese Ministry of Health, Labor and Welfare conducted a study to find the PAM patients in Japan. It was revealed that there are only seven patients with PAM currently alive in Japan. It has been thought that there are many PAM patients in Japan, but it suggested that the number of PAM patients is decreasing as a result of the decrease in consanguineous marriage after the world war ll. Based on these data, we will report on the current status of PAM in Japan. #2 New Biomarker and Treatment Strategy for PAM We have already reported that a low-phosphate diet prevented and/or diminished microlith formation in PAM mouse model. However, although phosphate dietary restriction is easily accomplished in mice, phosphate is ubiquitous in the human diet and attempts to limit intake are often unsuccessful. Phosphate binders are widely used in hyperphosphatemic patients with CKD. We found that oral administration of phosphate binders to PAM mice attenuated the microlith burden in the lung without appreciable adverse effects. Also, we found that COX-2 was clearly down-regulated under this treatment, which seems to be a useful biomarker for PAM. These results suggest that phosphate binders may be a useful adjunct to dietary phosphate restriction in the treatment of PAM.