– Autoimmune disease that invades muscles and surrounding tissues by itself due to abnormalities in the immune system
-Polymyositis and dermatomyositis are typical… Decreased muscle mass and muscle atrophy
-Invasion of internal organs may cause interstitial lung disease, heart failure, and dysphagia
– A ‘rare disease’, which occurs in 2 to 8 cases per 1 million people annually… 1.5 times more women
– Diagnosed by muscle biopsy… 20-30% of dermatomyositis is accompanied by cancer, examination is required
-Early diagnosis and treatment are important… Beware of side effects when using steroids for a long time
When our body considers its own normal tissues and cells as an attack target and causes an abnormal immune response, it is called an ‘autoimmune disease’. Representative examples include rheumatoid arthritis, systemic lupus erythematosus, Sjogren’s syndrome, systemic sclerosis, polymyositis, and dermatomyositis.
Inflammatory myositis is a muscle disease in which inflammation occurs when muscles and surrounding tissues are attacked by an autoimmune mechanism. These include polymyositis and dermatomyositis. Also, rare inclusion body myositis and immune-mediated necrotizing myositis are inflammatory myositis. When inflammatory myositis occurs, muscle tissue is destroyed, resulting in loss of strength and muscle pain. In addition, over time, muscle mass decreases, resulting in muscle atrophy.
Kim Moon-young, professor of rheumatology at Catholic University of Korea Incheon St. Mary’s Hospital, said, “Inflammatory myositis is an autoimmune disease that occurs when the body’s immune system is abnormal and attacks its own muscles. Treatment results have improved significantly due to the introduction of the drug, and the prognosis is good if detected and treated early.
◇ Symptoms vary depending on the affected area… Muscle atrophy and weakness, mainly
Symptoms vary depending on the area being attacked. In polymyositis, muscle strength gradually weakens over a period of weeks to months. Muscle weakness is more pronounced in the larger muscles on the side closer to the trunk. Movements such as sitting and standing, going up and down stairs, and lifting heavy objects become difficult, and muscle pain is often accompanied. In severe cases, it invades the muscles in the esophagus, making it difficult to swallow food, and breathing difficulties may occur as the heart muscle is invaded or the muscles related to breathing weaken.
Dermatomyositis, like polymyositis, is accompanied by muscle weakness and characteristic skin lesions on the face, trunk, and hands. Because of the light purple rash on the upper eyelid of the eye, it may look like makeup, and you can see a characteristic skin rash on the back of the hand joint.
Inclusion body myositis is characterized by progressive inflammation and degenerative changes in the extremity muscles, resulting in muscle atrophy and muscle weakness, and poor treatment.
Professor Kim Moon-young said, “In addition to the muscles, it may invade internal organs, but if shortness of breath due to interstitial lung disease or myocarditis occurs due to interstitial lung disease, heart failure or arrhythmia may occur. , gastroesophageal reflux disease, diarrhea or constipation, etc. may occur.”
◇Diagnosis by muscle biopsy… Because there are many accompanying cancers, examination is necessary
As with most autoimmune diseases, the exact cause is still unknown. However, it is believed to be caused by a combination of several genetic and environmental factors. Viruses and some drugs are mentioned as triggers, but it is not a genetic disease.
Polymyositis and dermatomyositis are known to occur in about 2 to 8 cases per 1 million people per year. The male to female ratio is 1:1.5, and it occurs more frequently in women. In children, it mainly occurs in the form of dermatomyositis, whereas in adults, both polymyositis and dermatomyositis can occur.
Once inflammatory myositis is suspected, measurements of several muscle enzymes in the blood can determine the extent of muscle destruction. However, among these enzymes, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are also increased during liver damage, so there are cases in which hepatitis is incorrectly diagnosed. A diagnosis should be made by a specialist taking into account the clinical symptoms.
In addition, muscle invasion is confirmed through imaging tests such as autoantibodies in the blood or MRI (magnetic resonance imaging), and neuroelectromyography is performed to distinguish it from other diseases such as neuropathy.
Professor Kim Moon-young said, “The most accurate diagnostic method for inflammatory myositis is muscle biopsy, and it is important to read it by an experienced pathologist.” In particular, inflammatory myositis can be accompanied by cancer. As they are found together, they must be tested,” he emphasized.
◇Early diagnosis and treatment are important… Beware of side effects when using steroids for a long time
Steroids are mainly used for treatment and, if necessary, additional immunosuppressants are used. 70-80% of patients show complete or partial remission. However, it may take about 2 months or more to recover the muscle strength felt by the patient. After that, it is necessary to maintain the steroid for at least several months, and the amount is reduced over time. However, long-term use of steroids may cause side effects such as osteoporosis, gastric ulcer, weight gain, and worsening of diabetes.
Unfortunately, there is no way to prevent it. However, functional recovery can be expected through early diagnosis and treatment. If treatment is delayed, the prognosis is known to be poor. It is so important to detect and treat it as soon as possible.
Professor Kim Moon-young said, “Immune suppressants are used in combination to reduce side effects when steroids are used for a long period of time, but side effects of each drug must also be closely monitored. Cooperation with various departments that can cope with complications is essential,” he emphasized.