Idiopathic inflammatory myopathy: Get informed

IMM is characterised by inflammation of muscle cells. It causes various symptoms affecting the muscles.


Idiopathic inflammatory myopathy


IMM is a group of rare autoimmune diseases characterised by inflammation of muscle cells. It mostly affects the muscles.

IMM includes such diseases as dermatomyositis, polymyositis, overlapping myositis, inclusion body myositis, cancer-associated myositis and necrotizing autoimmune myopathy.


Myositis is characterised by a great variability of symptoms, which vary depending on the form of the disease, but can also differ from patient to patient, even if they are affected with the same form.

Myositis causes muscle weakness, muscle pain and increased fatigue during physical effort.

Other symptoms may appear as well. For example, dermatomyositis also affects the skin, in addition to muscles.

Causes and risk factors

IMM develops as a result of the immune system malfunction, which leads to inflammation, provoking the symptoms. IMM is said to be idiopathic because no specific cause of this disorder has been identified.

According to recent studies, genetic predisposition, together with some environmental factors, could be a possible cause of the disease.


IMM affects about 6 to 7 people per 100,000.

They can occur at any age. Inclusion body myositis (IBD) most often develops after the age of 50. Dermatomyositis can affect children under 10.

The diagnosis can be made following a clinical examination (the doctor questions the patient about the development of the symptoms and does a physical examination to look for signs of the disease) and muscle examination called electromyogram (EMG) carried out using electrodes (needles or patch) . These examinations are followed by muscle biopsy, which allows the study of muscle cells under a microscope.


The aim of IMM treatments is to modulate the activity of the immune system in order to reduce inflammation. Different types of medications can be used: corticosteroids, immunosuppressants, immunoglobulins (a type of antibodies) or even targeted therapies. Blood plasma exchange can also be considered.

It is worth mentioning that inclusion body myositis is little or not at all sensitive to the usual treatments for IMMs. However, its development is very slow, and can take up to several years.

Physical therapy is also a way to treat IMMs. It helps to regain muscle strength.

Living with the disease

Most patients with IMM get better with treatment, and even go into remission. Some people may face a relapse, but the majority recover their muscle function completely.

It may be helpful to be accompanied by an occupational therapist (a health professional who helps the patient to adapt his or her environment so as to be able to perform day-to-day tasks without difficulties) and to set up some necessary equipment at home, in order to be able to function independently: medical bed, home healthcare services to help with the toilet, for example, etc.

Some modifications can be made to the patient’s car, depending on the extent of muscle damage, so that he or she could continue driving. However, a medical examination is necessary to assess if the patient is fit to drive.

Due to the significant impact of the disease on the patient’s daily life, psychological care can be of use: therapy can help the patient accept the illness, and learn to live with it.

Published 3 Dec 2021

avatar Alizé Vives

Author: Alizé Vives, Pharmacist, Data Scientist

Alizé holds a PharmD and a master's degree in strategy and international business from ESSEC Business School in France. She has several years of experience working with patients and members, conducting surveys for... >> Learn more

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