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Dermatomyositis

Pathogenesis

Julie Paik, MD, MHS 
Reviewed on February 14, 2025
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Mechanisms and Contributing Factors

The pathogenesis of Dermatomyositis (DM) is multifactorial, and influenced by genetic, environmental, and immunological factors. Inflammatory mediators may play a role in DM pathogenesis. Type I interferons, which regulate both innate and adaptive immune responses, play a key role in DM pathogenesis. DM is thought to be caused by a humoral mediated attack against the muscle capillaries and the endothelium of arterioles (Figure 1-1). Activation of complement mediators is followed by formation and deposition of the membrane attack complex on vascular walls, leading to inflammation, endothelial cell death and ischemic muscle fiber damage. Increased release of proinflammatory cytokines and chemokines upregulate the expression of adhesion molecules on the endothelial cell membrane, facilitating the migration of activated CD4+ T cells, B cells, and macrophages to the endomysial tissue. Hypoxic injury to the muscle fibers results in atrophy of muscle fibers,…

Mechanisms and Contributing Factors

The pathogenesis of Dermatomyositis (DM) is multifactorial, and influenced by genetic, environmental, and immunological factors. Inflammatory mediators may play a role in DM pathogenesis. Type I interferons, which regulate both innate and adaptive immune responses, play a key role in DM pathogenesis. DM is thought to be caused by a humoral mediated attack against the muscle capillaries and the endothelium of arterioles (Figure 1-1). Activation of complement mediators is followed by formation and deposition of the membrane attack complex on vascular walls, leading to inflammation, endothelial cell death and ischemic muscle fiber damage. Increased release of proinflammatory cytokines and chemokines upregulate the expression of adhesion molecules on the endothelial cell membrane, facilitating the migration of activated CD4+ T cells, B cells, and macrophages to the endomysial tissue. Hypoxic injury to the muscle fibers results in atrophy of muscle fibers, particularly those at the periphery furthest from the vascular supply. Over time, the capillary density reduces, and muscle fibers experience necrosis and degeneration.

Enlarge  Figure1-1: Pathogenesis of dermatomyositis. Source: Reprinted with permission: Chandra T, Aggarwal R. A Narrative Review of Acthar Gel for the Treatment of Myositis. Rheumatol Ther. 2023 Jun;10(3):523-537. doi: 10.1007/s40744-023-00545-1. Epub 2023 Mar 26. PMID: 36966453; PMCID: PMC10140234.
Figure1-1: Pathogenesis of dermatomyositis. Source: Reprinted with permission: Chandra T, Aggarwal R. A Narrative Review of Acthar Gel for the Treatment of Myositis. Rheumatol Ther. 2023 Jun;10(3):523-537. doi: 10.1007/s40744-023-00545-1. Epub 2023 Mar 26. PMID: 36966453; PMCID: PMC10140234.

Adults and children with DM show similar distributions of CD4 and CD8-positive cells in muscle, though children have more CD4 in perimysium while adults had more CD20 and CD68-positive cells.

References

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