What is Myositis?

May 12, 2020

Myositis is a type of inflammatory myopathies that are most commonly thought to impact the muscles (which they do) but they can also affect the heart, lungs, GI tract, and be associated with the development of cancer.  Myositis is considered autoimmune in nature; in it the body begins attacking its own muscles, connective tissue, skin, blood vessels and other organs.  It is estimated that between 50-75,000 people in the U.S. have one of the forms of myositis.  This makes it among the rare diseases.  As such, there are no dedicated treatments or therapies that have been developed specifically for any of the inflammatory myopathies. 

Broadly there are three main types of myositis: dermatomyositis, polymyositis, and sporadic inclusion body myositis.  Typically, the easiest to diagnose because of its hallmark, purplish, skin rash, is dermatomyositis. The rash that accompanies dermatomyositis most often forms on the face, upper back, chest, elbows, knees, and knuckles.  It is more typical for muscle weakness to come later in the progression of dermatomyositis.  After the disease process starts to take hold, vasculitis, or swelling of the blood vessels, begins to cause the muscles closest to the core of the body to become weakened.  It is most common for the muscle weakness to be symmetrical and progressive.  As with polymyositis, the kinds of drugs used to treat dermatomyositis are typically immunosuppressive and anti-inflammatory drugs.  Often, high dose prednisone is used to try and halt the disease’s rapid progression, while drugs like Azathioprine, Mycophenolate, and Methotrexate might be used for long-term treatment.

Sporadic inclusion body myositis (sIBM) is the most common of the inflammatory myopathies and generally impacts individuals after the age of 50; because of its slow progression experts aren’t actually sure that’s when the disease typically starts, but it is most commonly diagnosed after that age.  Unlike the other forms of myositis that may be relapsing/remitting in nature, sIBM is progressive – the body is continuing to atrophy once the illness has been acquired.  This form is distinct a couple of other ways too.  Unlike other forms of myositis, the weakness in sIBM is not necessarily symmetrical its presentation.  Also, rather than wasting that begins with the proximal, or core muscles, sIBM often begins with distal muscles like the feet, hands, ankles and lower legs.  Having difficulty with falls, balance, or drop-foot, are common complaints at the onset of sIBM.  The symptoms of sIBM and rate of progression varies significantly from person to person and can speed up or slow down over time with little rhyme or reason.  Because of its many faces and difficulty to diagnose, patients with sIBM often go undiagnosed for many years, their diseases are also often misdiagnosed as the effects of aging, as MS, or as polymyositis.

Polymyositis, like other myotises, is often referred to as a “muscle wasting” disease.  Inflammatory cells work into the fibers of smooth (skeletal) muscle tissue and burst the muscles, dissolving them right off the bone.  It can be slow or rapid in its progression and can be more difficult to identify because it does not have any external markers (like dermatomyositis’ rash) to make it evident.  It is most common for polymyositis to begin, like dermatomyositis, with the core or proximal muscles being symmetrically impacted.  For me, my complaints began with things like, “I’m having trouble rising from a seated position.”  I started needing assistance getting off the couch or toilet.  Then progressed to I can’t lift my arms above my head to wash my hair, and eventually the inability to roll over in bed without assistance and having difficulty swallowing.  Unfortunately, once muscle fibers are destroyed, they cannot be recreated.  Therefore, the rehabilitation after the onset or relapse of the condition (both poly and dermatomyositis are relapsing/remitting conditions) are arduous and contingent upon beefing up what muscle remains.  Like dermatomyositis, the drugs used to treat polymyositis are typically immunosuppressive and akin to the drugs given to RA patients.

Rheumatologists specialize in the treatment of rheumatologic or autoimmune diseases.  Therefore, it is typical for those of us with a myositis to have a rheumatologist (if we are lucky) to monitor our condition and treatment.  However, I live in a city with a population of approximately 175,000 people and see a very competent rheumatologist and I am his ONLY myositis patient.  In addition to seeing a rheumatologist, because of the way these diseases impact multiple systems, it might also be necessary to have a neurologist, dermatologist, and/or cardiologist, consult about aspects of the pathology.

While these diseases are said to not have any genetic link, the only other person I have known with polymyositis is my mother.  So… That leads me to believe that they don’t have enough evidence to understand what the genetic links of these diseases may be.  What is also true is that those of us who have one autoimmune condition are at great risk for having multiple autoimmune conditions.  Fun.  May is Myositis Awareness Month.  Thanks for hanging in here and educating yourself about this rare disease.  If you are seeking resources for yourself or a loved one about these muscle-related conditions, you can get more information, find connections, and learn from experts at Myosits.org and UnderstandingMyosits.org.


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