Early decrease in intermediate monocytes in peripheral blood is characteristic of multiple system atrophy-cerebellar type

To identify biomarkers for multiple system atrophy-cerebellar type (MSA-C), we used flow cytometry to measure surface marker expression of peripheral blood monocytes from patients with MSA-C or hereditary spinocerebellar degeneration (hSCD) and from healthy controls (HCs). The percentage of intermediate monocytes was significantly lower in MSA-C patients than in hSCD patients and HCs and showed significant positive correlations with disease duration and unified MSA rating scale scores. The percentage of CD62L⁺ intermediate monocytes was significantly lower in MSA-C patients than in hSCD patients and HCs. Early decrease of peripheral blood intermediate monocytes is characteristic of MSA-C and is a biomarker.