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What Causes Myositis

What Causes Myositis

What Causes Myositis And Can It Be Prevented?

Exactly what causes myositis is unknown, but research suggests that it is caused by a combination of factors. These include genetic predisposition, environmental triggers such as infection or exposure to certain medications or chemicals, and other autoimmune diseases. A person’s risk for developing myositis can also increase if they have an existing condition that weakens the immune system. Some research suggests that myositis may be caused by a virus or bacteria, but it is still not certain what role these pathogens play in causing myositis.

It is important to note that there is no single cause of myositis and researchers continue to investigate possible causes. Knowing the cause of a person’s myositis can help in determining the best treatment options for managing their condition. Additionally, further research into understanding the causes of myositis may eventually lead to better treatment and even prevention of this debilitating disease.

Autoimmune Conditions That Cause Myositis

Myositis is an inflammatory condition that affects the muscles. It can be caused by a variety of autoimmune diseases, including polymyositis, dermatomyositis, and inclusion body myositis.

Polymyositis is an autoimmune disorder in which the body’s immune system attacks its own muscles, causing inflammation and weakness. It can affect muscle groups all over the body, including those in the arms, legs, and face. Symptoms of polymyositis may include muscle weakness, muscle pain or tenderness, difficulty swallowing, and fatigue.

Dermatomyositis is another autoimmune disorder that can cause myositis. It is characterized by a skin rash as well as inflammation of the muscles. The most common symptom of dermatomyositis is a purplish-red, scaly rash on the face, chest, and back. Other symptoms may include muscle weakness, difficulty climbing stairs, and swallowing difficulties.

Inclusion body myositis (IBM) is an autoimmune disorder that causes progressive muscle weakness, primarily in the hands and feet. It can also cause difficulty swallowing and muscle pain. IBM is more common in people over the age of 50.

Myositis can also be caused by other autoimmune diseases, such as lupus, rheumatoid arthritis, and scleroderma. These diseases cause inflammation all over the body, including in the muscles. They may also cause fatigue, joint pain and swelling, skin rashes, and other symptoms.1

What Causes Myositis

Common Autoimmune Conditions

There are over 23 million people in the US who are affected by autoimmune diseases. Known autoimmune conditions include Rheumatoid Arthritis, Lupus, and Multiple Sclerosis.

Rheumatoid Arthritis is a condition that causes chronic inflammation in the joints and other areas of the body, resulting in pain, fatigue, and stiffness.

Read more about Rheumatoid Arthritis.

The condition called Systemic Lupus Erythematosus is an autoimmune disease that can cause inflammation in any part of the body. It is also capable of harming organs like the heart, lungs, skin, and kidneys.

Read more about Lupus.

The neurological disorder known as Multiple Sclerosis gradually affects the brain and spinal cord. Its symptoms may include vision problems, muscle weakness, sensations changes, and fatigue.

Read more about Multiple Sclerosis.

What Causes Myositis – Infections

Infections are one of the most common causes of myositis. Bacterial, viral, and fungal infections can cause inflammation in the muscles, leading to damage and pain. Viral infections such as influenza, human parvovirus B19, HIV/AIDS, Epstein Barr virus (EBV), cytomegalovirus (CMV), and enteroviruses, can cause inflammation and lead to myositis. Bacterial infections such as staphylococcus aureus and group A streptococcus may also be the culprits. In rare cases, fungal infections have been linked to myositis.2

Parasitic infections are another cause of myositis. These infections can be caused by a variety of different parasites, such as roundworms, tapeworms, and hookworms. Some types of parasites, such as those found in contaminated food or water, can cause infection when they enter the body through the skin or digestive system.3

What Causes Myositis – Drugs

Certain drugs are known to cause myositis. Many drugs, both prescription and over-the-counter (OTC), can cause an inflammatory response in the muscles. This can manifest as myositis or other related conditions such as dermatomyositis, polymyositis, and inclusion body myositis.

Common medications associated with myositis include hydroxychloroquine (Plaquenil), statins, simvastatin (Zocor), atorvastatin (Lipitor), lovastatin (Mevacor), and fluoroquinolones. Other drugs such as antiretrovirals, anticonvulsants, benzodiazepines, and some antibiotics can also trigger myositis.4 5 6

What Causes Myositis – Muscle Injury

Muscle injury is one of the most common causes of myositis. This can be due to a traumatic event such as an accident or overexertion, or it can develop gradually over time through poor posture and ergonomics, repetitive motions, and other activities that increase strain on the muscles. If left untreated, muscle injury can cause inflammation in the affected muscles, leading to myositis. Treatment for muscle injury-related myositis typically involves rest, physical therapy, and medications to reduce inflammation and pain. If the injury is severe enough, surgery may be necessary to repair the affected muscles.7

What Causes Myositis - Muscle Injury

Myositis And Interstitial Lung Disease

Myositis and interstitial lung disease (ILD) are two different medical conditions that are often linked together. ILD is a broad term that describes any type of inflammation or scarring of the lungs. Both of these conditions can lead to a variety of respiratory symptoms, and may even cause breathing difficulties.

Research has shown that people with myositis are at an elevated risk for developing ILD or other lung diseases. This is because myositis can cause inflammation in other areas of the body, including the lungs. Additionally, certain medications used to treat myositis can also increase the risk of developing ILD.8

What Causes Myositis – Genetics

Myositis can be caused by certain inherited genetic mutations as well as environmental factors. It has been found that people with certain family histories are more likely to develop the condition, suggesting a genetic component. Studies have also shown an increased risk of myositis in individuals who have particular HLA-DRB1 gene variants.9

What Causes Myositis – Environmental Factors

Some environmental factors that are responsible for causing myositis include exposure to certain toxins, such as those found in industrial waste, occupational or residential pesticides, and solvents.

What Causes Myositis – Organophosphorus Pesticides

Organophosphorus Pesticides (OPs) are widely used in agriculture and are known cause myositis. Long-term exposure to OPs can lead to muscle weakness, fatigue, and cramps. OPs cause muscle damage and inflammation when ingested or inhaled. Exposure to these products results in an inflammatory response in the body, which leads to muscle weakness and stiffness.10

Additionally, certain pesticides may contain heavy metals that can act as neurotoxins, further contributing to muscular problems such as myositis. People who work in agricultural fields or with products that contain pesticides may be especially at risk of developing this condition. To reduce the risk, people should avoid unnecessary contact with these products and wear protective clothing when necessary.

What Causes Myositis – Air Pollution

Air pollution is composed of a variety of particles, such as ozone, nitrogen dioxide, and particulate matter. These substances can irritate the airways and cause inflammation throughout the body. This can lead to an increased risk for autoimmune diseases, like myositis. Research has shown that people living in urban areas with higher levels of air pollution are more likely to develop myositis than those living in rural areas.11

What Causes Myositis – Prenatal Exposure To Tobacco Smoke

Research suggests that children born to mothers who smoked during pregnancy have an increased risk of developing myositis. It is believed that prenatal exposure to tobacco can cause the body’s immune system to be weakened, resulting in a higher likelihood of developing an autoimmune disorder like myositis.12

What Causes Myositis - Prenatal Exposure To Tobacco Smoke

What Causes Myositis – Vitamin D Deficiency

Vitamin D deficiency is one of several potential causes of myositis. Vitamin D helps to maintain strong muscles as it helps the body absorb calcium, and when the levels are too low, muscle weakness can develop. People who have a vitamin D deficiency due to diet or lack of sun exposure may be more prone to developing myositis.

Low levels of vitamin D have been linked to several types of autoimmune illnesses including myositis. Vitamin D can reduce inflammation in the body which has a direct impact on muscle tissue. Without enough vitamin D, it can be difficult for the body to repair damaged muscle fibers, leading to the development of myositis.13 

In addition to dietary changes and taking supplements, increasing sun exposure is the best way to increase Vitamin D levels in the body.

Read more about how crucial vitamin D is for those suffering from autoimmune conditions.

What Causes Myositis And Can It Be Prevented?

Exactly what causes myositis includes genetic factors, prenatal factors, and environmental factors. As with any other autoimmune condition, improving lifestyle choices as well as ensuring optimal vitamin D intake reduces the risk of developing these conditions.

Read more about what causes autoimmune conditions.


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3 El-Beshbishi SN, Ahmed NN, Mostafa SH, El-Ganainy GA. Parasitic infections and myositis. Parasitol Res. 2012 Jan;110(1):1-18. doi: 10.1007/s00436-011-2609-8. Epub 2011 Sep 1. PMID: 21881948.

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8 Hallowell RW, Paik JJ. Myositis-associated interstitial lung disease: a comprehensive approach to diagnosis and management. Clin Exp Rheumatol. 2022 Feb;40(2):373-383. doi: 10.55563/clinexprheumatol/brvl1v. Epub 2021 Mar 25. PMID: 33769263; PMCID: PMC8855729.

9 Lamb JA. The Genetics of Autoimmune Myositis. Front Immunol. 2022 May 26;13:886290. doi: 10.3389/fimmu.2022.886290. PMID: 35693792; PMCID: PMC9178267.

10 Karalliedde L, Baker D, Marrs TC. Organophosphate-induced intermediate syndrome: aetiology and relationships with myopathy. Toxicol Rev. 2006;25(1):1-14. doi: 10.2165/00139709-200625010-00001. PMID: 16856766.

11 Zhao N, Smargiassi A, Chen H, Widdifield J, Bernatsky S. Systemic autoimmune rheumatic diseases and multiple industrial air pollutant emissions: A large general population Canadian cohort analysis. Environ Int. 2023 Apr;174:107920. doi: 10.1016/j.envint.2023.107920. Epub 2023 Apr 8. PMID: 37068387.

12 Orione MA, Silva CA, Sallum AM, Campos LM, Omori CH, Braga AL, Farhat SC. Risk factors for juvenile dermatomyositis: exposure to tobacco and air pollutants during pregnancy. Arthritis Care Res (Hoboken). 2014 Oct;66(10):1571-5. doi: 10.1002/acr.22358. PMID: 24757124.

13 Glueck CJ, Abuchaibe C, Wang P. Symptomatic myositis-myalgia in hypercholesterolemic statin-treated patients with concurrent vitamin D deficiency leading to statin intolerance may reflect a reversible interaction between vitamin D deficiency and statins on skeletal muscle. Med Hypotheses. 2011 Oct;77(4):658-61. doi: 10.1016/j.mehy.2011.07.007. Epub 2011 Jul 29. PMID: 21802861.

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