Definition and Overview

Myositis is a rare muscle disease. It is marked by chronic muscle inflammation and weakness. It can be acute (symptoms develop suddenly but resolve on their own after some time) or chronic (symptoms are longer-lasting). It can result in muscle loss and death of muscle tissue. Thus, it can be debilitating.

The disease can cause a number of complications. Some of which can be fatal. Patients with swallowing problems (when the chest and lung muscles are affected) are at risk of inhaling food and fluids into their lungs. This can increase their risk of dying.

There is no known cure for it. But its symptoms can be improved with medical and physical therapy.

Causes of Condition

Most cases occur when the immune system attacks the muscles and connective tissue. This causes the muscles to swell and symptoms to appear. Other cases are due to exposure to toxic substances as well as infectious disorders, such as HIV or AIDS.

Key Symptoms

Patients have weak and swollen muscles. This can make everyday movements difficult. This can occur suddenly or slowly over weeks or months. Sometimes, it can even take years.

The different types of the disease cause different signs. These are as follows:

  • Polymyositis - Affects both sides of the body. It affects muscles around the thighs, back, and hips. It can also affect the neck and shoulders. Its signs develop slowly over weeks or months. The risk of the disease increases with age. It is common in 35-44 and 55-64 age groups. It can make climbing stairs and rising from a sitting position difficult. When left treated, it can lead to swallowing problems and even heart failure. It can affect both men and women. But women are two times more prone to it.

  • Dermatomyositis - Marked by muscle weakness accompanied by a purple or red rash. The rash appears on skin that covers muscles used to straighten or extend the joints. These include the toes, knees, elbows, and knuckles. This type can affect both children and adults. It is more common in women than men. Aside from muscle weakness and skin rash, its other symptoms are sensitivity to light and low-grade fever. It can also cause calcium deposits to form under the skin or in the muscle.

  • Post-infectious reactive myositis (PIRM) - Occurs following some types of viral infections. When compared to the first two types, this one is milder. It is not a cause for concern. It can get better on its own after some time.

  • Inclusion body myositis (IBM) - Often affects older men aged 50 and above. It can weaken the muscles of the wrists and fingers. It also affects the main thigh muscles as well as muscles below the knee. It is marked by muscle wasting that worsens over the course of years. Its signs are falling and tripping more often and swallowing problems. It also makes gripping objects more difficult.

Who to See and Types of Treatments Available

Diagnosing the disease starts with a physical examination and blood tests. The goals are to measure muscle strength and check the levels of antibodies and enzymes in the blood. Other tests used are magnetic resonance imaging (MRI) and electromyography (EMG). MRI is a modern scanning tool that can show the severity and extent of the condition. EMG, on the other hand, assesses how electrical signals travel from nerve endings to the muscles. Muscle biopsy can be used to confirm a diagnosis. It involves using a sample of muscle tissue to look for signs of inflammation and muscle damage.

The disease is treated with drugs that stop the immune system from attacking the muscles and connective tissue. Steroids can also be used. These mimic the effects of certain hormones that are naturally produced by the body. When taken in high dosages, these drugs are able to suppress inflammation.

Patients also have to undergo physical therapy to preserve their muscle strength and maintain range of motion. A gentle exercise programme is appropriate if there is intense muscle pain and weakness. The level of exercise can be increased as the condition improves. Medical therapy can be combined with immunoglobulin or biologic therapy. This becomes necessary in patients with life-threatening symptoms, such as severe swallowing problems.

Most patients respond fairly well to therapy. However, other factors can affect their prognosis. The outlook tends to be poor when they have underlying medical conditions. The same is the case for those with severe muscle weakness that causes swallowing problems.

Unlike other forms of the disease, IBM is generally not responsive to all therapies. Available treatments do little to keep it from worsening.


  • National Institute of Neurological Disorders and Stroke.

  • Belman AL, Preston T, Milazzo M. Human immunodeficiency virus and acquired immunodeficiency syndrome. In: Goetz, Pappert, eds. Textbook of Clinical Neurology. 1999:898-900.

  • Patel SR, Olenginski TP, Perruquet JL, Harrington TM. Pyomyositis: clinical features and predisposing conditions. J Rheumatol. 1997 Sep. 24(9):1734-8

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