The results of bisulfite pyrosequencing showed that CTSG (DM patients 22.17 ± 2.70, PM patients 18.44 ± 2.18), NE (DM patients 17.22 ± 1.74, PM patients 14.88 ± 1.67), and PR3 (DM patients 14.28 ± 1.82, PM patients 13.50 ± 2.59) were hypomethylated in DM/PM patients compared to normal controls (CTSG 42.17 ± 1.02, NE 31.26 ± 1.05, PR3 24.05 ± 2.05), but the difference between DM patients and PM patients was not obvious (CTSG P = 0.2975, NE P = 0.3388, PR3 P = 0.8017) (Fig. 1d–f). Here, PRTN3 is linked to polymyositis.