Abstract
Discriminating an autoimmune myositis from other disorders and subtyping of patient groups within this heterogeneous group of conditions remain diagnostic challenges. In our study we explored the potential of cytokine and chemokine typing in patient sera as an addition to the expanding set of blood-accessible diagnostic biomarkers available today. We selected sets of ten patients within well-characterized disease groups representing healthy controls, and patients with hereditary muscular dystrophies, immune-mediated necrotizing myopathy (IMNM) and sporadic inclusion body myositis (IBM). Prescreening using proteome arrays singled out three biomarker candidates, being the cytokine CD40L, and chemokines CXCL10 and CCL5. Enzyme-linked immunosorbent assays showed all three markers to be elevated in muscle disease irrespective of patient subgroup. CXCL10 levels on the other hand were higher in autoimmune myositis only, and levels were significantly higher in IBM compared to IMNM. The strong CXCL10 expression observed in the auto-aggressive inflammatory cells within IBM muscle tissues possibly represents a major source of circulating CXCL10. We conclude that CXCL10 levels could represent a convenient marker for autoimmune myositis indicative of patient subgroups.