IFIH1 and dermatomyositis: The expression levels of SIP and dhS1P were higher in MDA5+DM group than in other groups, and the expression levels of dhSph (the precursor of dhS1P) were increased in DM-ILD, suggesting a potential relationship between MDA5+ and ILD, and the important role of sphingosine metabolism in anti-MDA5+ and ILD.