What are inflammatory myopathies?
There are several inflammatory myopathies that affect different parts of the body. A myopathy is a condition that affects the muscles. The result is often inflammation in the muscles, with weakness, in coordination and sometimes severe pain.
Inflammatory myopathies, also known as idiopathic inflammatory myopathies, are a group of conditions that cause chronic inflammation and weakness in muscles. While there is no known cause for these conditions, doctors believe that they may be autoimmune diseases. This means that the body’s immune system attacks itself and damages muscles, tissues, joints, or even organs. It’s easier for a doctor to find the cause of muscle inflammation than to find a direct cause for inflammatory myopathies. Those causes include an infection or virus and an allergic reaction to medication. These don’t necessarily cause muscle disease, but they do contribute to muscle weakness.
Symptoms of inflammatory myopathy
Those with this muscle disease commonly experience muscle weakness in the hips, shoulders, and neck and have difficulty climbing stairs, standing up from a seated position, or reaching for objects that are just out of reach. Very rarely do people experience pain with this condition. Specific symptoms, however, depend on the type of the inflammatory myopathy with which a person is diagnosed.
Types of inflammatory myopathies
- Inclusion body myositis (IBM): Sporadic inclusion body myositis is the most common type in individuals who are 50 years or older and tends to present itself in men more than women. This disease is known to progress gradually, but individuals with this type of muscle disease can find themselves in a wheelchair within 10 to 15 years due to atrophy in the muscles. This disease can affect both proximal muscles (the muscles that are closest to the center of the body) and distal muscles (the muscles that are furthest from the center of the body). While it’s more common for individuals to experience muscle weakness on both sides of the body, it’s possible for individuals to only be affected on one side of the body. As the muscles begin to weaken, individuals with this disease will begin having difficulties walking. They may be seen tripping or falling. They may have difficulty grasping objects and buttoning shirts or pants. They may also experience difficulty swallowing or speaking. Certain proteins may clump together in the muscle that contain toxins. These clumps are similar to the ones found in neurodegenerative diseases such as Alzheimers. The presence of these clumps can only be confirmed through a muscle biopsy.
- Dermatomyositis: This type of inflammatory myopathy affects the skin in the form of a rash followed by muscular dystrophy. A red or purple rash will appear on the skin that covers the joints such as the knuckles, elbows, knees, and toes and may even appear over the eyelids. A red rash can also appear over the larger muscles such as the back, chest, shoulders, neck, and face. Hard bumps may appear under the skin or in the muscle tissue, which are formed by calcium deposits. Exposure to the sun could worsen the rashes. The affected areas may become inflamed, which can diminish muscle strength. Other symptoms include inflamed lungs, low-grade fever, difficult swallowing, weight loss, and difficulty speaking. This disease progresses slowly, but could begin in childhood as well as adulthood. This disease is known to affect women more than men.
- Polymyositis: This type of inflammatory myopathy affects the large muscles on both sides of the body like the hips, neck, shoulders, thighs, and upper arms. These muscles become progressively weaker, which is makes it hard for people to climb stairs, lift heavy objects, getting up from a seated position, and try to grab for things that are just out of reach. Some people have difficulty breathing, swallowing, and even speaking. Others may develop arthritis, a heart arrhythmia, or even congestive heart failure. This type of muscle disease typically progresses slowly, but in rare cases can progress quickly. It mainly occurs in men and women between the ages 30 and 60. The diagnosis for this condition is often related to ruling out other types of myopathy.
- Necrotizing autoimmune myopathy: Necrotizing myopathy is rare, but can be mainly affects adults. Symptoms of this disease include proximal muscle weakness, which can result in difficulty getting up from a seated position, climbing stairs, and lifting heavy objects. Other symptoms can include extreme muscle pain, fatigue, and weight loss. While most inflammatory myopathies progress slowly overtime, this disease progresses quickly. Individuals may reach the peak of this disease within days or weeks. While the disease can occur on its own, it’s more common that it occurs in tandem with cancer, viral infections, connective tissue disorders such as scleroderma, or in those taking statins (cholesterol lowering medication). Even if individuals on cholesterol lowering medication decide to stop taking said medication, the pain and muscle atrophy can worsen.
Doctors can suspect that a patient could have one of these diseases when they communicate that they are experiencing difficulties doing certain tasks that require muscle strength. This becomes more obvious when the patient presents rashes along with muscle weakness. If a doctor suspects that the patient could have an inflammatory myopathy, they’ll conduct a muscle strength test to identify any areas of muscle weakness. If their initial tests confirms that the muscles are weak, they’ll confirm the diagnosis by testing serum creatine kinase levels, conducting an electromyography, and by performing a muscle biopsy.
Creatine kinase is a substance that is released into the bloodstream when muscle fibers are deteriorating. Conducting a blood test can help doctors understand whether or not levels of this substance are high. Very high levels of creatine kinase may be indicative of dermatomyositis or polymyositis, but those with inclusion body myositis may only have slightly elevated levels. This is why doctors tend to perform more than one test when diagnosing these diseases.
The next test that a doctor will perform is an electromyography. This test shows how the nerves and muscle function are working together by measuring the electrical signals in the muscle tissue, nerves, and nerve roots. This test is conducted with a tiny needle electrode that is inserted into the muscle through the skin. The electrode is a conductor for electrical current. Once the electrode is inserted, doctors can begin measuring the amount of electricity that the muscle cells are generating when they become activated by a nerve pulse. Doctors can confirm the diagnosis of inflammatory myopathy if the muscle fibers don’t respond well to the repeated stimulation since normal functioning muscles do respond well to this test. The results of this test can often lead doctors to creating a treatment plan to help manage symptoms.
Other tests that doctors may perform include a muscle biopsy and magnetic resonance imaging (MRI). A biopsy requires doctors to remove a piece of the affected muscle to test for inflammation or muscle fiber death. If hard bumps are under patients’ skin, doctors can also biopsy those to diagnose dermatomyositis. However, this test mainly helps doctors rule out other causes like muscular dystrophy. An MRI can show doctors where there are abnormal muscles in the body, but this isn’t the best test to provide a definite diagnosis. Blood tests and the electromyography are the two tests that can really help doctors come up with a definite diagnosis.
Treatment of inflammatory myopathy
Unfortunately, there isn’t a cure for these inflammatory muscle diseases. Treatment is often based on treating the symptoms. Medication is always the main course of treatment when it comes to treating symptoms. Corticosteroids, such as prednisone, are often the first medication doctors prescribe. Side effects of corticosteroids includes weight gain, thinning of the skin, cataracts, osteoporosis (loss of bone mass), and even muscle weakness. This type of medication often returns blood muscle enzymes back to normal after about four to six weeks, which is why this is often the first course of treatment.
The second course of treatment, or even an additive to the first course of treatment, is a disease modifying antirheumatic drug (DMARD) such as methotrexate or azathioprine. These medications help to reduce inflammation and don’t come with the damaging long-term side effects that corticosteroids have. This is why most doctors will swap out the course of treatment long-term. If the disease is severe, individuals may be given an intravenous immunoglobulin (IVIg) treatment, cyclosporine, mycophenolate mofetil, tacrolimus, or rituximab. Doctors will also encourage patients to go through physical therapy and consistent exercise routines to aide muscle movement.
