Changes in Gene Expression Profile in the Muscles of Patients with Dermatomyositis and Inclusion Body Mysoitis After Therapy with Intravenous Immunoglobulin: A Microarray Analysis Correlating Gene Expression with Clinical Outcomes

Dermatomyositis (DM) is an inflammatory muscle disease affecting muscle and skin. It is characterized by early deposition of complement on the intramuscular capillaries leading to capillary destruction, muscle ischemia, perifascicular atrophy, inflammation consisting of B cells, CD4+cells, and to a lesser degree CD8+ cells, intense up-regulation of cytokines and adhesion molecules, and endomysial fibrosis. In contrast, sporadic inclusion body myositis (sIBM) is a chronic inflammatory muscle disorder with intense endomysial inflammation consisting of CD8+ T cells that invade major histocompatibility complex (MHC) class-I expressing muscle fibers along with vacuolar degeneration of muscle fibers and amyloid deposits1,2.