SDHB and Parkinson disease: A recent characterization of small EVs from the serum of PD patients identified a reduction in the levels of mitochondrial markers such as adenosine triphosphate 5A (ATP5A), NADH: ubiquinone oxidoreductase subunit S3 (NDUFS3), and succinate dehydrogenase complex iron sulfur subunit B (SDHB), and of the levels of the tetraspanins CD9 and CD63 (97).