A Rare Cause of Muscle Weakness

Having trouble getting up out of a chair? Going up and down stairs? Getting in and out of a car? If so, you may be experiencing the effects of muscle weakness. Muscle weakness is a fairly common problem as we get older and in those who are physically deconditioned (i.e., “couch potatoes”). Another term for anything that’s wrong with the muscles is myopathy (myo = muscle and pathy = pathologic or diseased).

But muscle weakness or myopathy could also be caused by a wide range of medical problems such as infections, endocrine diseases, muscular dystrophies, cancer, and neurologic conditions. Other causes of muscle weakness include drug toxicity, rheumatologic diseases (e.g., fibromyalgia, sarcoidosis), and vitamin deficiency.

In this report, a rare cause of muscle weakness is discussed: inflammatory muscle disease. Doesn’t ring any bells for you? That’s because it only affects one in five million adults in the United States. But for those individuals, early diagnosis and treatment is important for the best outcomes.

Who is affected? Inflammatory muscle disease is actually age- or gender-linked depending on what type of muscle disease is involved. There are three basic types of inflammatory muscle disease: 1) polymyositis, 2) dermatomyositis, and 3) inclusion body myositis.

Polymyositis only affects adults, whereas dermatomyositis is seen in children and adults. Inclusion body myositis is rare in anyone younger than 50 and occurs most often in men over the age of 60.

People who develop any of these three inflammatory muscle diseases develop symptoms slowly over months to years. Muscle weakness affecting the shoulders and hips is first. That’s when patients with this disease start to notice difficulty sitting up and down from the toilet, putting something up on a high shelf, or brushing the hair.

No one really knows what brings this inflammatory muscle disease on. That’s why they are referred to as idiopathic (unknown cause). And because there are so many other potential causes of muscle weakness, it can take quite a while to figure out what’s going on. Dermatomyositis is the only one that has a characteristic facial rash to help point the right direction in searching for a diagnosis. It’s also the only one to be associated with a history of cancer.

Just how does the physician make the final diagnosis? It requires a number of different steps starting with a thorough history (personal and family history) and timeline for symptoms. Lab tests help sort out infections from inherited muscle diseases and from endocrine disorders such as Addison disease, Cushing syndrome, and thyroid problems.

There are some specific lab tests just for muscle diseases. For example, measuring blood levels of an enzyme called creatine kinase (CK) may be helpful. CK is elevated in all three types of inflammatory myopathies. An increase in CK doesn’t always point to inflammatory muscle disease(s).

High levels of CK can occur as a result of trauma, medications, and even exercise. There are even times when the CK levels are normal but the person really does have an inflammatory muscle disease.

Whenever the lab values come back normal, it’s back to the diagnostic drawing board so-to-speak. The physician will recheck for other subtle signs and symptoms such as difficulty swallowing or speaking, heart or lung problems, and skin rash. Some additional lab studies may be ordered. And imaging studies (MRIs), X-rays (chest and abdomen) electromyography (EMGs), and muscle biopsy may be ordered.

By themselves, none of the tests and measures can diagnose inflammatory muscle diseases. The physician must really rely on all the diagnostic clues and information provided by each one. All put together, it is possible to rule out other causes of the muscle weakness until the only reasonable possibility is inflammatory myopathy.

At that point, treatment is the next step. Most often, the patient is referred to a specialist who sees more than an occasional case now and then. Medical therapy begins with antiinflammatory drugs (e.g., corticosteroids) to reduce inflammation. If one drug doesn’t work, it may be necessary to combine several drugs together to get the intended result.

Exercise (aerobic or cardio and strength training) is a key feature of treatment. Exercise will not make the disease worse and has been shown to make things much better. Exercise will help keep the weakness from getting worse rapidly. It’s still likely that strength will continue to decline but it will happen at a much slower pace.

Physical activity and exercise are also important in keeping the joints moving and preventing muscle and joint contractures (soft tissues get stuck on one position and can’t stretch or move). Patients must be educated to understand that exercise has its own anti-inflammatory effects and should be a part of each day.

For anyone who would like a detailed review of inflammatory muscle diseases, this article provides some helpful tables, photos, and descriptions of each one. Patient evaluation, diagnosis, and treatment are discussed in detail as well.