In summary, we found that the 5 key genes, C1orf106, COG8, EVPL, GIMAP6, and IFI6, were associated with the CD4+ T-cell infiltration in lesional skin tissues of DM, and the prediction model constructed based on the 5 key genes may better also predict the level of CD4+ T-cell infiltration in damaged muscle tissues of DM. The gene discussed is COG8; the disease is dermatomyositis.