Patients usually have a history of recent illness (fever, URI symptoms, etc)
Significant myalgias as starting to improve from constitutional symptoms
Most commonly lower legs
Can have pain and tenderness in other muscle groups (thighs, arms)
Usually look well, but will sometimes walk with wide gait and on their toes
When lying in bed, will often keep toes pointed with pain in calves upon dorsiflexion
Most commonly lower legs
Can have pain and tenderness in other muscle groups (thighs, arms)
When lying in bed, will often keep toes pointed with pain in calves upon dorsiflexion
Myositis 
Infection:
Mucositis
Viral infection 
Leukopenia
Bacterial infection
Eosinophilia
Spirochete infection 