Unexplained inflammation in muscles is known as "myositis", a condition that affects about 15 in 100,000 people. The muscles affected usually include those around the shoulders and hips, but other parts of the body can be affected. Unlike other muscle diseases, such as muscular dystrophy, the inflammation in myositis is potentially treatable, although the drugs used can be toxic and don't always work. As myositis is uncommon, doctors are often not familiar with recognizing the disease. Delays in diagnosis may lead to irreversible muscle damage, so even after treatment has started, sufferers often remain weak and disabled, leading to significant illness burden on families, carers and society.