Inflammatory Myositis - What is it for

Also known as muscle inflammation, inflammatory myositis is a rare condition that can affect people all ages.

There are two main clusters of patients; children between the ages of 5 to 15 years and adults between the ages of 30 to 65 years. Generally, women are twice more likely to develop myositis than men.

This condition causes the muscle to be weak and can also result in muscle ache and swelling. There are many types of inflammatory myositis but the major types include:

Dermatomyositis

In addition to muscle weakness, there may be a rash on the skin, especially around the eye-lids and the fingers. Cancer is found in approximately 10%-20% of cases. Sometimes, the muscle problem develops first. In other cases, the cancer is detected before the myositis.

Polymyositis

The condition may affect the muscles alone without a rash. Cancer is not commonly associated with polymyositis, unlike in dermatomyositis.

Inclusion body myositis

The condition causes severe muscle weakness and wasting throughout the body over a long period of time.

Drug-induced myositis

The condition is triggered by the body's response to a type of cholesterol lowering drug called statins. The symptoms of muscle pain and weakness can manifest over a short period of time, but patients can also improve rapidly once the medication is stopped.

Inflammatory Myositis - Symptoms

The major symptoms common to all forms of inflammatory myositis are muscle weakness and muscle pain. Other symptoms vary, depending on the specific cause of the disease.

In dermatomyositis and polymyositis, weakness usually affects muscles near the centre of the body like the neck, shoulders and hips. Patients can experience difficulty with simple tasks like combing their hair, dressing, getting into a car, and standing up from a sitting position or climbing stairs. About one third or half of such patients also have problems swallowing and often choke when drinking fluids. Some patients with dermatomyositis and polymyositis also have lung involvement which results in cough and breathlessness.

General symptoms like lethargy, fatigue, weight loss and poor appetite are also very common.

When to seek help

If any of the following persists, please get in touch with our team as soon as possible:

Muscle pain and weakness that is progressive and does not go away with rest
A red or purplish rash on your face or around your eyes
Muscle pain and weakness that begins after you start taking a new medication like a cholesterol-lowering drug
If you have been diagnosed with myositis and develop a fever, cough or other forms of infection like skin infection, abscess or pain on passing urine

All infections in patients with myositis need to be treated urgently and aggressively with antibiotics and often in hospitals.

Inflammatory Myositis - How to prevent?

Inflammatory Myositis - Causes and Risk Factors

Inflammatory Myositis - Diagnosis

Due to the many different forms of myositis and similarities to other muscular and nerve diseases, it may take a few visits to the doctor before the condition can be diagnosed.

After a careful physical examination, the doctor will order other tests to confirm the diagnosis. Such tests may include:

Routine tests like a full blood count, erythrocyte sedimentation rate (ESR), and c-reactive protein (CRP) test

Blood tests for muscle enzymes and auto-antibodies. Muscle enzyme levels (usually raised initially) are useful for monitoring progress and response to treatment

Electromyogram (EMG): This is a test that measures the electrical activity of muscles. In patients with myositis the EMG would be abnormal

Muscle biopsy: The doctor takes a sample of the affected muscle to be checked under the microscope. The procedure is done under local anaesthesia

X-ray of the chest: To investigate for lung cancer and lung involvement associated with myositis

Magnetic Resonance Imaging (MRI): This painless scan can identify abnormal muscles and can be used to locate the best site for a biopsy and to monitor the progress of the disorder

A chest and abdominal CT scan: This test is useful to investigate for hidden cancers

Gastroscopy and colonoscopy: These tests are useful to investigate for underlying cancers in the gastrointestinal tract

Inflammatory Myositis - Treatments

While there are no known cures for myositis at the moment, treatment strategies aim to alleviate symptoms and manage the progression of the condition through the following methods:

Medications

For dermatomyositis and polymyositis, doctors usually start with high dose corticosteroids (eg. prednisolone) for about 4 – 6 weeks. When the condition improves the dosage is then slowly reduced. Other immunosuppressive treatments may be added (eg. methotrexate).

Intravenous immunoglobulin (IVIG) (an injection of antibodies) may occasionally be effective in cases that fail the above first-line treatments. If IVIG is effective, it needs to be continued on a long term basis, although in lower doses to maintain the effect.

Another form of treatment in patients who do not respond well to conventional drugs is plasmapharesis or plasma exchange. This is a type of blood cleansing in which the damaging antibodies are removed from the blood. Often the effect is temporary.

In patients with drug-induced myositis, the medication causing the myositis will need to be stopped and replaced with an alternative. At the moment there is no effective treatment for inclusion body myositis.

Exercise

Physical therapy and specially designed exercise programmes are very important for recovery of muscle strength.

Dermatomyositis associated with cancer

Treatment of the underlying cancer should take priority either by surgery, chemotherapy or radiotherapy.

Most people with dermatomyositis and polymyositis eventually regain their strength with proper treatment. But there are risks of complications such as infections at the lungs arising from swallowing and breathing difficulties.

Inclusion myositis usually progresses very slowly and does not affect a person’s lifespan unless complications like infections set in. In most cases of drug-induced myositis, the symptoms subside when the offending drug is stopped.

What you can do

If you are suffering from myositis, here's what you can do to cope:

Know your illness. Discuss with your doctor and nurse and seek more information from reliable sources
Have adequate rest and sleep. Eat a nutritious diet and pace your daily activities. Do not overdo things or tire yourself. Stretch often and do gentle exercises at home
Keep a positive attitude and do not isolate yourself
Wear sunscreens when you go out into the sun, especially if you have a rash

Inflammatory Myositis

Inflammatory Myositis | Singapore General Hospital