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Myositis: an autoimmune condition

Myositis encompasses a group of rare autoimmune conditions. An autoimmune condition is one where our body’s defence system starts to mistakenly attack its own cells. Why this happens is not clearly understood. In Myositis the body’s immune system attacks muscle cells, resulting in inflammation and weakness.

Symptoms

The symptoms, including which muscles are affected, depends on the type of myositis present, but generally all forms will present with muscle weakness, poor endurance and fatigue.

The main types of Myositis are:

1. Dermatomyositis (DM) is characterised by muscle weakness around the neck, shoulders, trunk, and hips (proximal muscles). This may present as difficulty climbing stairs, getting up from a chair, reaching overhead, walking difficulties and even falls.

The key characteristic of DM is presence of a rash on the body, around the eyes, hands or feet. This is due to inflammation around small blood vessels in the muscles and skin.

Swallowing and breathing difficulties may also be present.

The gastrointestinal tract and lungs can be affected in some cases.

2. Polymyositis (PM) has similar symptoms to dermatomyositis but without the rash type symptoms. Both have also shown to have increased cancer risks.

 

3. Inclusion Body Myositis (IBM) has a very distinct pattern of muscle weakness. Hand and wrist flexor weakness presents as decreased grip strength, trouble writing and picking things up. Quadricep (thigh) muscle weakness makes it difficult to get up from a chair or climb stairs. Tibialis anterior (at the front of the shin) weakness causes the foot to drop and can produce tripping and falls. IBM is more common in men and usually presents in middle to later age.

4. Necrotising Myositis (NM) (or Necrotising Autoimmune Myopathy) can have symptoms of sudden and extreme muscle weakness. The characteristics of this sub group are similar to PM, which it was previously classified under. However, findings on muscle biopsy differ (higher levels of muscle cell death) and different autoantibodies are present in blood tests, so its classification has changed. It has been associated with the use of statin medication, although this is rare.

 

5. Juvenile Myositis (JM) is found in children under the age of 18, the most common form being Juvenile Dermatomyositis (JDM) – with skin rash symptoms often over eyelids or joints. Fatigue, irritability and complaints of stomach aches often accompany muscle weakness of the proximal muscles and legs. A hoarse sounding voice or swallowing difficulties may be present. Juvenile Polymyositis (JPM) will not have a rash present.

Diagnosis

A diagnosis of Myositis is made by a Specialist Rheumatologist or Neurologist and will include a thorough examination, blood tests (to look at muscle enzymes and antibodies) muscle biopsy and/or scans of muscles.  Nerve conduction tests may also be done.

Treatment

There is currently no cure for Myositis. It is managed with medication (such as steroids and immunosuppressive drugs), exercise and supportive therapies. Research is currently underway in Australia and overseas to better understand the condition.

Exercise

Recent studies in patients with PM and DM have shown that exercise is safe and does not increase the inflammation or CK (creatinine kinase, a muscle enzyme) in muscle tissue. It can improve muscle function, aerobic capacity and quality of life.

Exercise prescription will depend on your current physical capacity, aimed at maintaining the muscles affected by myositis and those to aid in daily living and general mobility. It is a good idea to consult with a Physiotherapist who can assess your current level of functioning and can formulate an exercise plan to suit your individual needs. You will need to start slowly and build up, monitoring fatigue levels as you go.

Reaching a diagnosis of Myositis often takes many years. Raising public awareness and health provider knowledge about Myositis and its symptoms can play a part in reducing this time. So thank you for reading!

If you would like more information on Myositis visit Myositis Australia:

https://myositis.org.au

~Sarah Jarvie

Sarah was lucky enough to attend The Third National Conference of the Myositis Association of Australia in May this year.

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