SIGLEC1 and inclusion body myositis: In SaM patients, the copy number also goes along with the expression level of multiple genes, as we identified significant elevation of CCL5, GPNMB, IFNG, IL1B, LMP2, PERK, SIGLEC1, TGFB and TNFA in SaM patients where mitochondrial copy number was pronouncedly reduced (MTND1 < B2M; n = 8, including both patients with SaM‐IBM) in comparison to those where mitochondrial copy number was only mildly reduced (MTND1 > B2M; n = 10) (Figure S7c,d).