Polymyositis and Dermatomyositis

What are polymyositis and dermatomyositis?

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Polymyositis and dermatomyositis are connective tissue disorders. These are types of myositis, which is the name for a group of conditions that cause weak, aching, and painful muscles. These diseases affect the body’s tendons, ligaments, and the collagen-based tissue that covers muscle ends. Polymyositis and dermatomyositis are chronic conditions that do not have cures. While not exceedingly dangerous on their own, these conditions can lead to complications, including cardiovascular problems, lung problems, and organ inflammation.

Polymyositis and dermatomyositis are rare, but they can be very difficult to live with. Excessive pain and weakness can make daily tasks difficult, and symptoms will typically get worse over time. If you think you may have any type of myositis, schedule a visit with your doctor. They can provide insight and a diagnosis, as well as any treatments or therapies you may need.

What is the difference between polymyositis and dermatomyositis?

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While grouped collectively under the term “myositis,” polymyositis and dermatomyositis are different conditions. Polymyositis is characterized by muscle weakness and inflammation. This weakness generally develops over time, making it difficult to perform daily tasks – climbing stairs, turning over in bed, and brushing hair, among others. In polymyositis, the muscle weakness is generally symmetrical, meaning that if you experience pain in your left arm, you are likely to experience a similar pain in your right arm. The muscle weakness is most often experienced in the body’s proximal muscles, including the upper arms, shoulders, neck, thighs, and hips.

By contrast, dermatomyositis involves the same muscle inflammation and weakness, but it is often accompanied by a skin rash. This rash comes before or accompanies the muscle weakness. In some cases, muscle weakness may not be a major symptom of the disease. Like with polymyositis, the affected muscles are typically symmetrical and proximal, including the thighs, upper arms, shoulders, hips, and neck.

Polymyositis and dermatomyositis often occur concurrently. If your doctor diagnoses one, they will run tests for the other.

What are the causes of dermatomyositis and polymyositis?

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There is no known cause of polymyositis and dermatomyositis. Many researchers think the conditions are the result of an immune reaction in the body against its own tissues. In some cases, viruses can play a role, and a tumor may contribute to an outsized immune system reaction. Other inflammatory conditions, like lupus, scleroderma, and rheumatoid arthritis, can cause mild forms of myositis. In fact, most of the symptoms overlap, so if you have lupus or scleroderma, your doctor will likely test for dermatomyositis and polymyositis.

In many cases, myositis is an underlying condition for other diseases, including pulmonary disorders and cardiac involvement, like arrhythmia, pericarditis, and congestive heart failure.

What are common polymyositis and dermatomyositis symptoms?

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Though separate conditions, dermatomyositis and polymyositis symptoms overlap significantly. It is important to remember that symptoms typically present gradually, but they can also appear suddenly, such as after an infection. These symptoms are also associated with lupus and scleroderma, which means that only tests and a physician can provide a definitive diagnosis.

  • Difficulty swallowing. This can happen when the muscles in the throat and esophagus are affected.
  • Shortness of breath. Gradual damage and weakness in the chest wall can impact the muscles that move the diaphragm while breathing.
  • Muscle weakness. In most cases, this is not noticeable until the disease is advanced, or when around half of the muscle fibers have been destroyed. Weakness can be severe, limiting a person’s ability to raise the arms above their shoulders. If the neck muscles are affected, a person may not be able to lift their head from a pillow. The weakness is often symmetrical and affects the proximal muscles, like the shoulders, thighs, hips, chest, and neck.
  • Fatigue
  • Arthritis
  • Low-grade fever
  • Tripping or falling

If dermatomyositis accompanies polymyositis, a person may also experience the following symptoms.

  • Bumps on the knuckles, elbows, and knees (known as Gottron’s papules)
  • Dry, rough, and/or scaly skin
  • Scalp itchiness or hair loss, sometimes resembling psoriasis
  • Weight loss
  • Flaking and weak cuticles, as well as blood vessels on nail folds

Additionally, both polymyositis and dermatomyositis occur more often in women than men, as well as in people ages five to 15 and 40 to 60.

While these symptoms may not seem urgent to most people, they can indicate something more serious. If you experience any of these signs, make an appointment with your doctor or a rheumatologist to get a diagnosis.

How are polymyositis and dermatomyositis diagnosed?

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A polymyositis and/or dermatomyositis diagnosis will often involve a physical exam. During this, the doctor will assess muscle weakness and look for the characteristic dermatomyositis rash. If the doctor has reason to believe you have a type of myositis, they will conduct one or more test to confirm the diagnosis.

  • Blood tests – High levels of muscle enzymes, like creatine kinase, can indicate muscle inflammation. Additionally, blood tests can check for abnormal antibodies, which may help to identify an autoimmune condition.
  • Muscle biopsy – This is the most accurate test for diagnosis myositis. If the doctor can identify a weak muscle, they will make a small incision and remove the sample for testing. This biopsy often leads to a final diagnosis.
  • Magnetic resonance image (MRI) scan – An MRI can create images of muscles. This can help a doctor identify areas affected by myositis, as well as whether muscles change over time.
  • Electromyography (EMG) – This test involves inserting electrodes into muscle using a needle. The doctor can use this to test muscle response, helping to identify muscles that have been weakened or damaged by myositis.

If a doctor suspects dermatomyositis, they will also check for any cancerous tumors and provide additional cancer screenings.

It is important to remember that polymyositis and dermatomyositis are rare conditions, which makes them difficult to diagnose. Myositis can present differently in each person, and diagnoses may be delayed if characteristic symptoms are not present.

How are polymyositis and dermatomyositis treated?

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Dermatomyositis and polymyositis treatment focuses on reducing inflammation and other symptoms. There is no known cure for these conditions, but when following a treatment, a person can significantly restore muscle performance and improve their quality of life.

The only approved therapy for polymyositis is corticosteroids, like prednisone or prednisolone. This medication will reduce inflammation and help suppress an overactive immune system. Sometimes, this treatment is administered intravenously. However, corticosteroids are not recommended for long-term use, as they have many side effects. This can include weight gain, the redistribution of body fat, elevated blood sugar levels, and a thinning of a person’s skin.

Most doctors will recommend additional drugs to suppress the immune system. These immunosuppressive drugs may often reduce or eliminate the need for steroids, but they come with their own risks. Cytotoxic drugs, which were originally developed for cancer treatment, can be used to treat some cases of polymyositis.

There are also a range of therapies that can improve dermatomyositis and polymyositis symptoms.

  • Immunoglobulin therapy – This intravenous therapy involves immunoglobulin, which comes from antibodies extracted from donated plasma.
  • Rituximab – This type of drug, provided intravenously, is a form of antibody therapy.
  • Acthar gel – This is a corticotropin delivered by injection. Acthar gel causes the release of cortisol from a patient’s adrenal glands, mimicking the effects of corticosteroids without the side effects. Acthar can also reduce immune overactivity.

Those with dermatomyositis are also advised to avoid the sun and use high-SPF sunscreen, UV protected apparel, large-brim hats, and sunglasses.

What is the outlook for patients with polymyositis and/or dermatomyositis?

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Living with dermatomyositis and/or polymyositis can be challenging. In most cases, it will require some lifestyle changes and the acceptance of a “new normal” until you find a therapy or treatment that works for you. While muscle weakness is a primary symptom of both conditions, exercise can be vital to living with myositis. Whether it’s physical therapy, some type of physical rehabilitation, or low-impact exercise, these steps can help strengthen muscles. Just check with your doctor to see which option will work best for you.

Nutrition and diet are also essential for living with polymyositis and/or dermatomyositis. A well-balanced diet high in protein can be very beneficial. If you’re not sure where to begin, as your doctor for a referral to a dietician.

While living with these inflammatory conditions can be difficult, constant management can significantly improve your quality of life. If you think you may have dermatomyositis or polymyositis, talk to your doctor. Only a physician can provide a diagnosis, but once you have an answer, you can begin making the changes necessary to improve your life and health.