ATG5 and primary progressive multiple sclerosis: Our results demonstrated that the serum level of the autophagy markers ATG5 and ATG7 (Figure 1A,B) and the mitophagy markers OPTN and Parkin (Figure 1C,D) were lower in MS subjects affected by the PPMS form than in those with the RRMS form and in control (CTRL) individuals (Kruskal–Wallis test: p < 0.0001).