Polymyositis is a condition where there is chronic inflammation of the muscles. The inflammation is found to be mostly in the endomysium, the smallest and deepest component of the muscle connective tissue. It is a condition where there is defective cellular immunity which is believed to be associated with other systemic autoimmune conditions. Polymyositis is believed to have occurred due to diverse causes or in association with connective tissue disorders, viral infections, or malignancies. Studies have shown that it is a T-cell mediated cytotoxic process causing it to be directed against muscle antigens.
While the factors that trigger the T-cell mediated process are still unclear, viruses such as the human immunodeficiency virus (HIV) and coxsackie virus have been implicated. In the United States, polymyositis is estimated to be more common among the black population. Internationally, the incidence of polymyositis is lower among the Japanese. This condition is also more common among women compared to men. It usually affects those above the age of 20 with peak incidence among those 45 to 60 years old. Polymyositis usually has a good prognosis as it responds well to treatment. However, it has been observed that approximately 30 percent of patients experience residual weakness.
Symptom #1: Muscle Weakness
Muscle weakness is also known as myasthenia. It occurs when there is decreased or lack of muscle strength. There can be many causes of myasthenia where it could be categorized into true or perceived weakness. In true weakness, the causes include skeletal muscle diseases such as inflammatory myopathy, muscular dystrophy, and myasthenia gravis. It can also be due to electrolyte imbalances like low potassium levels.
Weakness can be short or long-term depending on the underlying cause and treatment the patient is able to receive. In polymyositis, the muscle weakness is often in the proximal muscles which is often bilateral causing the inability to get up from a sitting position or to raise their arms above their head.