Myositis is the name for a group of rare conditions that can cause muscles to become weak, tired and painful.
The word myositis simply means inflammation in muscles. If something is inflamed, it may be swollen.
Myositis can affect people of any age, including children.
The main muscles to be affected are around the shoulders, hips and thighs.
Having myositis can also lead to other parts of the body being affected, such as the skin, lungs or heart.
Sometimes myositis can affect the muscles that carry out tasks such as breathing and swallowing.
There are several types of myositis. The two most common types are polymyositis and dermatomyositis.
‘Poly’ means many. Polymyositis means that many muscles are affected by inflammation. This type doesn’t often affect other parts of the body much.
Dermatomyositis causes similar symptoms in muscles, but there is also a skin rash. ‘Derma’ means skin.
Polymyositis, dermatomyositis, as well as other types of myositis, are autoimmune conditions.
The immune system is the body’s natural self-defence system. When healthy, it protects us from infection, injury and illness.
However, in people who have autoimmune conditions, the immune system gets confused and mistakenly attacks the body’s own healthy tissues.
One feature of a healthy immune system is inflammation. For example, when we have a cut, the body sends fluid to the affected area so that white blood cells can fight off any infection.
If someone has an autoimmune condition the body can create inflammation when there is no infection to fight. The unnecessary inflammation can then cause problems.