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The term myositis means inflammation of the muscles. The inflammation is usually progressive and can cause pain, swelling, rashes, and muscle hardening. Mainly skeletal muscles around the shoulders, hip, and thighs are affected, which causes weakness and fatigue. Still, in severe cases, it also involves internal organs such as the heart and lungs.  


Multiple reasons can cause myositis. The most common cause is when the body’s immune system starts attacking the muscles and causes inflammation which is the body’s autoimmune response. It can also be caused by common cold and flu viruses which invade muscles and cause direct injury to the muscles. Muscle myopathy can also be caused by adverse reactions or drug toxicity. These drugs may be statins, colchicine, cocaine, and alcohol. Extreme exercise or training for too long can also cause muscle injury leading to myositis.


After a few similar symptoms, myositis can take a few different forms.


If, before any muscle weakness, you experience an unusual skin rash, it may be the condition of dermatomyositis. The skin rash looks dark and patchy. It occurs mostly on the upper body, including the eyelids, face, knuckles, elbows, upper back, and chest. It can also affect the knees. In some conditions, there may also be the presence of small hardened bumps under the skin called calcinosis. Once the muscle weakness starts, it involves muscles close to your trunk, which are muscles of the shoulder, hips, thighs, neck, and upper arms. This condition affects more women than men. If the patient suffers no muscle pain with the rash, they are said to have amyopathic dermatomyositis.


In patients with polymyositis, it starts with weakness in the muscles near the trunk, spreads in the distal muscles, and worsens. Polymyositis can also involve breathing and the alimentary tract muscles, so the patients may suffer difficulty breathing and swallowing. People with polymyositis often eventually have trouble walking, running, and difficulty getting up after a fall. It affects people with age over 20 years and affects more women than men. With increasing age, the risk of getting polymyositis increases.

Juvenile myositis

It occurs in children aged between 5-15 years. It starts with a characteristic skin rash that is red-purplish and dry, along with muscle weakness caused by inflammation in the blood vessels, i.e., vasculitis. Many children with juvenile myositis also have pain in their muscles. Another common symptom is contractures that bend a joint due to the shortening of a muscle.

Inclusion body myositis:

This type is usually found in people over 50 years of age. It occurs genetically and is the only type that occurs more in men than women. It starts with muscle weakness around the distal parts of the arms and upper part of the legs. In this type, along with the inflammation, there is a buildup of small protein particles in the muscles, which can only be seen in the late stage of the condition with a microscope.

Toxic myositis

In this type, toxicity is caused by some medications due to inflammation in the muscles. Toxic myositis also has the same symptoms as other types, which can stop once we stop taking the medications causing it.

Risk Factors And Epidemiology

In most types of myositis, women are at higher risk of getting it than men. Increasing age is also another risk factor for myositis. In the United States, about 1600 to 3200 cases of myositis are enrolled yearly, and 50,000 to 75,000 people live with it.

Signs And Symptoms

The common sign of myositis is muscle weakness, with each type having more characteristic symptoms.

In dermatomyositis, the common symptoms are;

     Purple-red rashes.

     Gottron’s papules (bumps around the knuckles with raised dry breakout).

     Weakness in the neck, hip, back, and shoulder muscles.

     Trouble getting up from a fall.


Polymyositis can show symptoms that are;

     A severe weakness in the muscles near the trunk.

     Difficulty getting up from a fall.

     Dysphagia (difficulty swallowing).

Symptoms that are characteristic of juvenile myositis are;

     Purplish-red rashes.

     Difficulty reaching up with arms.

     General tiredness.

     Tummy aches.

     Rough, husky voice.

Inclusion body myositis is usually presented with the below-mentioned signs;

     Repeated falls.

     Trouble climbing stairs.

     Difficulty walking.

     Difficulty flexing fingers and writing.


Diagnosing myositis is often tricky, and it is misdiagnosed because it is rare, presents with symptoms like muscle weakness and fatigue, and occurs alongside other autoimmune diseases. A variety of methods make the diagnosis of myositis. Starting with a usual history with a practical physical examination followed by muscle biopsy, blood tests for muscle enzymes, magnetic resonance imaging, electromyography, and nerve conduction velocity tests.

Differential Diagnosis

Myositis, in general, is misdiagnosed with many other myopathies, including congenital myopathies, muscular dystrophies, metabolic myopathies, motor neuron diseases, diseases with raised creatine kinase, myasthenia gravis, and a variety of other metabolic disorders and drug-induced myopathies.


Basic treatment for myositis includes physical therapy, stretching, exercises, anti-inflammatory medications, and corticosteroids. Myositis involves autoimmune reactions and is treated with immunosuppressants that suppress the body’s immune system to stop attacking its muscles and organs.


The medications given are corticosteroids, such as prednisone. The immunosuppressants include azathioprine and methotrexate. 


The prognosis for myositis depends upon the type and severity of the body involved. For example, patients whose swallowing or breathing is involved may end up inhaling food or fluid into their lungs, and interstitial lung disease may develop, leading to death. However, patients with polymyositis and dermatomyositis are at higher risk than patients with inclusion body myositis. Normally, patients with myositis are still alive more than five years after their diagnosis.  


People with autoimmune diseases like myositis are advised to follow an anti-inflammatory diet plan, which includes avoiding fast, processed, and packaged foods, taking more fruits and vegetables, and increasing the intake of foods rich in omega-3 fatty acids such as salmon and flax seeds. Dietary supplements should also be taken to maintain the body's calcium, folic acid, and vitamin D levels.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 25, 2023.



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