Persistent maternally derived peripheral microchimerism is associated withthe juvenile idiopathic inflammatory myopathies

Objective. Fetal cells have been demonstrated in the active lesions of adul t women with systemic sclerosis. Because the juvenile idiopathic inflammato ry myopathies (JIIM) share clinical and histopathological features with sys temic sclerosis and graft-vs-host disease, we explored the possibility that maternal cells persist and play a role in the pathogenesis of JIIM. Methods. DNA samples extracted from peripheral blood of 28 JIIM patients (1 4 females. 14 males) and 23 healthy controls were assessed for microchimeri sm by the HLA Cw polymerase chain reaction method. HLA Cw alleles from eigh t mothers and three healthy siblings of JIIM patients were also examined. Results. A microchimeric allele was identified in 19 of 26 JIIM patients wh ose data were able to be interpreted, compared with two of 21 healthy contr ols (P<0.001). Subjects with microchimerism ranged in age from 4 to 28 yr. In eight cases in which maternal peripheral blood was available. the additi onal Cw allele present in the patients was confirmed to be identical to a m aternal allele. Three healthy siblings of JIIM patients did not have eviden ce of a microchimeric Cw allele. Conclusion. Maternal cells can persist in the peripheral blood of their chi ldren up to three decades after birth, and are found in a higher proportion in JIIM patients compared with controls. These findings, with other data, suggest that maternal cells may be involved in the immunopathogenesis of JI IM.