CD68 + macrophage infiltrations in muscle tissue of juvenile dermatomyositis associated with the course of the disease, not with the severity.

OBJECTIVE

To explore the relationship between the immunohistochemical characteristics of muscle tissue and clinical phenotype, and investigate the influencing factors of inflammatory cell infiltrations in muscle tissue in Juvenile dermatomyositis (JDM) patients.

METHODS

Nineteen JDM patients and five control patients were included in the present study. Immunohistochemical staining was performed on the muscle biopsies.

RESULTS

The macrophages and lymphocytes significantly increased in muscle tissue of JDM patients compared with the control group. The positive area proportions of macrophage infiltrations and T lymphocyte infiltrations in muscle tissue of JDM were linearly correlated (CD68 and CD3 r = 0.592, p < 0.001; CD68 and CD4 r = 0.690, p < 0.001; CD68 and CD8 r = 0.579, p < 0.001; CD163 and CD3 r = 0.649, p < 0.001; CD163 and CD4 r = 0.651, p < 0.001; CD163 and CD8 r = 0.763, p < 0.001). In JDM patients with a disease course < 1 year, the duration of disease is linearly correlated with the degree of CD68 + macrophage infiltrations in muscle tissue, and the longer the disease duration, the more CD68 + macrophage infiltrations in the muscle tissue (r = 0.283, p = 0.028). The positive area proportions of CD68 + macrophages and T lymphocytes (CD3 + , CD4 + , and CD8 +) infiltrating the muscle tissue of anti-PM/Scl75-positive JDM patients were significantly higher than those of anti-PM/Scl75-negative patients. The degree of T lymphocyte (CD3 + , CD4 + , and CD8 +) infiltrations in the muscle tissue of anti-NXP2-positive JDM patients was significantly lower than those of anti-NXP2-negative patients.

CONCLUSION

The CD68 + macrophages infiltrations of muscle tissues in JDM associated with the course of JDM, not related to disease severity. Key Points • The inflammatory cell infiltrations of muscle tissues associated with the course of JDM, not severity. • Macrophage infiltrations in muscle tissue of JDM are linearly correlated with T lymphocyte infiltrations. • The duration of disease is linearly correlated with CD68 + macrophage infiltrations in muscle tissue.