Females are affected more than men. Usually, it starts after around 18 years. Patients present with muscular weakness in the legs, spreading to upper limbs and then eventually to entire body. There is a sense of tiredness or fatigue, due to muscle involvement. Patients also complain of painful body movement due to inflammation of muscles. Increasing difficulty in getting up, running, climbing staircase, and eventually day to day activities, forms a major symptom of this disease. Polymyositis is a progressive condition, where more and more groups of muscles tend to get involved, leading to restricted mobility and increasing painfulness. It does not have a tendency to go into natural remission, as recorded in the cases at Life force. Symptoms are listed as follows:

Difficulty speaking
Difficulty swallowing
Fatigue
Weight loss
Low grade fever
Painful swelling in the small joints
Muscle soreness
Shortness of breath
Muscles feel tender to the touch
Muscle weakness, especially the hips and shoulders
Difficulty climbing stairs, lifting above the shoulders, and getting up from chairs