A rare but treatable collection of conditions, Prof Hector Chinoy discusses myositis

polymyositis, myositis, dermatomyositis, inclusion body myositis, Hector Chinoy, arthritis digest

Myositis is a rare autoimmune disease that involves an abnormal immune reaction against the body’s own organs, most commonly muscle, skin and lungs, which leads to inflammation.

The main symptoms are muscle weakness, pain, fatigue, rashes and shortness of breath. This usually gets slowly worse over time.

Who gets it?

Mostly adults but children can be affected too. The two main types of myositis are:

Polymyositis that affects many areas of muscle in the body but is not seen elsewhere in the body;

Dermatomyositis that affects muscle and skin.

However, there are even less common types of myositis such as inclusion body myositis, which causes progressive muscle weakness around the knees and hands. Necrotizing myopathy causes muscle cells to rapidly die and in very rare cases is triggered by taking statins.


There is no single test that can prove for certain you have myositis, but there are tests that can be helpful in making a diagnosis. A specialist will therefore arrange blood tests, electrical muscle tests, magnetic resonance imaging, muscle scans and muscle biopsies.

Specific antibodies produced by the patient’s immune system help with diagnosis. Scans and biopsies can show the extent of muscle inflammation and if there has been any damage to the muscles. The progression of the disease may differ depending on the type of myositis a person has.


Myositis is usually treated with steroids in tablet or injection form to begin with. The aim is to reduce inflammation and muscle pain along with the feeling of being unwell. But some people experience disease that is particularly aggressive or resistant to treatment and organ damage can occur. Side effects from steroids are common and may be serious.

New treatment options are becoming available, however, including biologic drugs that are more effective than steroids and have less severe side effects. Unfortunately, not all patients are eligible for biologics and some do not respond to them.

We need better ways to help predict who will best respond to available treatments. The Manchester Myositis Research Group is doing research into understanding what causes myositis and how treatments reduce symptoms. New treatments are in the pipeline. Watch this space!

Further information

Mary, age 73 from Cheshire, has immune-mediated necrotizing myopathy. Read her true story here.

Myositis UK, visit www.myositis.org.uk or tel 023 8044 9708.

About the author: Hector Chinoy is a Professor of Rheumatology and Neuromuscular Disease at The University of Manchester

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