Myositis: Diagnosis and Treatment
Robert Fink MD, Guest Reviews
Myositis is a general term used to describe inflammation of the muscles. A vast majority of cases are considered to be a consequence of an autoimmune disease, rather than an infection. That is why the term myositis is primarily used to describe rare disease wherein the immune system chronically inflames body’s healthy muscle tissue. Myositis is a tricky and poorly-understood condition that requires a precise and specific diagnosis to recommend a suitable treatment.
Causes of myositis
- Myositis can be caused by any condition which induces inflammation in the muscles. We can divide causes of this condition into several categories such as:
- Drugs – many medications and drugs have a potential to cause temporary muscle damage. That said, muscle inflammation usually goes unnoticed which is why the problem is often referred to as myopathy rather than myositis. Drugs that contribute to onset of this disorder include cocaine, statins, colchicine, alpha-interferon, alcohol, Plaquenil (hydroxychloroquine)
- Infections – here, the most common infections that lead to this condition are viral infections. In rare cases, the condition can also be caused by bacteria, fungi, or other organisms
- Inflammatory conditions – ones cause inflammation throughout the body and also affect muscles. The majority of these conditions are autoimmune i.e. the body attacks its tissues, but it’s unclear what triggers the body into “attacking itself.” Conditions that cause milder forms of myositis include lupus, rheumatoid arthritis, and scleroderma
- Injury – strenuous activities and vigorous exercises cause muscle pain, weakness, and swelling lasting from a few hours to a few days after the activity. Inflammation contributes to these symptoms, thus posing as a mild form of myositis
- Rhabdomyolysis – develops when muscles break down
In most cases, a patient reports the following symptoms:
• Difficulty breathing
• Difficulty swallowing
• Muscle pain
• Muscle weakness
• Thickening of the skin on hands
• Trouble climbing stairs, standing from a seated position, reaching up
Patients with myositis caused by a virus demonstrate symptoms of viral infections like a cough, runny nose, fever, sore throat, nausea, and diarrhea.
Since muscle pain can also be caused by many other conditions and diseases, it is necessary to advise patients to report any symptom they notice in a bid to rule out other diseases and order tests that could aid diagnosis of myositis.
- Myositis caused by inflammatory conditions can be categorized to the following forms:
- Dermatomyositis (DM) – damages both muscle fibers and skin. A patient develops muscle weakness, pain, and fatigue together with patchy skin and rashes on eyelids, cheeks, bridge of the nose, back or upper chest, elbows, knuckles, and knees. According to the Myositis Association, the condition is more prevalent among female rather than in male patients. For reasons that are still poorly understood, DM is usually found in African American women. This myositis type is the easiest to diagnose due to characteristic skin changes.
- Inclusion body myositis (IBM) – primarily occurs in patients over 50 who may experience dysphagia, weak wrists and/or fingers and atrophy of the forearms and/or thigh muscles. The condition affects men more often than women. Unfortunately, there are still no effective treatments for IBM. Only a small number of IBM cases are hereditary, a vast majority of them are sporadic meaning there’s no genetic link.
- Juvenile myositis (JM) – according to the Myositis Association, it affects 3000 to 5000 children and teens in the US. Children mostly get juvenile DM, cases of juvenile PM or IBM are rare. The very first sign of this condition is a skin rash.
- Polymyositis (PM) – weakens and inflames muscles in many parts of the organism, especially proximal muscles (closest to the trunk). Patients with this type of myositis exhibit dysphagia (difficulty swallowing) as well as fatigue and pain in muscles. PM affects patients over 20 years of age and is more prevalent among women.
In order to allow patient to recover and manage the pain, prompt and accurate diagnosis is mandatory. That can be a complicated task considering there are some conditions that are either related to myositis or have the similar name. For example:
- Myositis ossificans circumscripta – a benign, bony tumor caused by formation of bone in soft tissue after injury or trauma
- Myositis ossificans progressiva, also known as fibrodysplasia ossificans progressiva – rare, inherited disorder characterized by progressive fibrosis and ossification of tendons, muscles, fasciae, aponeuroses, and ligaments of multiple sites. The condition is disabling and ultimately fatal
- Panniculitis ossificans – similar to myositis ossificans but occurring in subcutaneous tissues
- Fibro-osseous pseudotumor of the digits – occurs in fingers and toes
Based on muscle weakness and other symptoms linked to myositis, you will already suspect about the possible diagnosis, but to be 100% certain and to rule out other conditions, some tests are necessary. They are:
- Blood tests – checking for abnormal antibodies that may identify an autoimmune condition. If blood tests also demonstrate high levels of muscle enzymes e.g. creatine kinase, it could indicate muscle inflammation
- MRI – identifies areas of myositis and changes in the muscles
- EMG – analyzing the response of muscles to electrical nerve signals. This test identifies muscles that are damaged or weakened due to the condition
- Biopsy of the muscle – the most accurate test for diagnosis of myositis. After identifying weak muscle, it is necessary to make a small incision and remove a sample of muscle tissue for testing. The same can be done with skin.
Treatment of Myositis depends on the type of the disease. In the paper composed by researchers at the National Institutes of Arthritis and Musculoskeletal and Skin Diseases and published in the Therapeutic Advances in Musculoskeletal Disease, the mainstay of therapy for inflammatory and autoimmune types of myositis is immunosuppression, physical therapy, and avoidance of complications. It is also necessary to introduce non medication modalities to maintain strength and overall function in patients. A major obstacle to the patient care is the fact that the FDA doesn’t approve a majority of medication treatment regimens. Another major consideration doctors and consultants should bear in mind is adequate monitoring for adverse effects because liver-associated enzymes are induced by inflamed muscles. It is crucial to watch a patient carefully in a bid to recognize potential liver toxicity propelled by active muscle disease.
- Following treatments are recommended for inflammatory types of myositis:
Drugs that suppress the immune system such as methotrexate, prednisone, azathioprine (Imuran). High-dose corticosteroids are dubbed effective, starting with prednisone at 1mg/kg per day with eventual taper after a few months to the lowest dose to maintain a remission. In patients with severe form of the disease, methylprednisolone at 1g per day is given intravenously for 3-5 days at the onset
- Physical therapy or customized exercise programs to prevent muscles from permanent shortening
When it comes to myositis caused by infection, in most cases no treatment is necessary. In rare instances caused by bacteria, antibiotics prove to be effective solution. A disease that is caused by drugs or medications is relieved when a patient discontinues usage of the agent that caused the condition. Cases, when myositis is caused by rhabdomyolysis, are rare, but when it happens a patient has to receive intravenous fluids in large quantities.
Myositis is a poorly understood and understudied condition affecting muscles. This can happen due to a variety of reasons. Proper and accurate diagnosis depends on tests performed as muscle weakness or pain can be caused by multiple conditions. It’s also essential to encourage the patient to report all symptoms experienced even if they regard them as unimportant.
Robert Fink, MD is a board certified Chicago orthopedic surgeon and one of only three surgeons in Chicago performing minimally invasive spine surgery. Dr Fink graduated from Loyola University Chicago’s Stritch School of Medicine and has been providing orthopedic surgery procedures for over 30 years.