n :  inflammation of several muscles at once : specif  :  an inflammatory disease of unknown cause that affects muscles and esp. skeletal muscles, is characterized typically by weakness usu. of the proximal muscles (as of the pectoral or pelvic girdles or of the neck), skin rash, muscle and joint pain, pathological muscle changes (as fiber degeneration or infiltration by lymphocytes), pneumonia, and cardiac abnormalities (as arrhythmia or myocarditis) - see DERMATOMYOSITIS  .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2004.