Fibromyalgia: Wide spread MSK pain, fatigue, depression. Females 20-50.
Polymyalgia Rheumatica: Sudden onset pain/stiffness in shoulders and hips, often with fever. No muscle weakness. Over 50 years old. Ass. with giant cell arthritis. Increased ESR.
Polymyositis: symmetrical proximal muscle weakness. Affects the shoulders, trouble getting up stairs, out of chairs. Over expression of MHC-1 leads to CD8 T cell destruction of myocytes. (+) ANA (+) Anti-Jo, Increased CK
Dermatomyositis: Polymyositis but with gattron papules, Malar rash, heliotrope rash (on eyelids), shawl and face rash. (+) ANA (+) Anti-jo, increased CK