Myositis with complications
Some people with myositis may experience overlapping conditions or complications.
What are complications?
Most autoimmune diseases are complex conditions meaning those with myositis may find that they experience symptoms of other medical issues alongside their condition. We refer to these as complications.
These complications can vary from breathing and swallowing issues, to calcium deposits, to other autoimmune diseases.
This page contains some of the most common complications, but it is not an exhaustive list. We recommend using the NHS website to find more details about each specific condition mentioned.
Myositis antisynthetase syndrome
Myositis antisynthetase syndrome is essentially the presence of specific autoantibodies in the body known as antisynthetase antibodies. It is a complication of polymyositis and dermatomyositis, but more recently we have tended to refer to it as a particular type of myositis itself rather than a complication.
Overlapping autoimmune diseases
Different autoimmune conditions frequently show similar symptoms which is why they can be hard to diagnose. Sometimes this may be a result of overlapping autoimmune diseases.
People with polymyositis and dermatomyositis are most likely to develop additional autoimmune diseases. Common conditions that overlap with myositis include rheumatoid arthritis, lupus, scleroderma and Sjögren’s syndrome.
These conditions are usually diagnosed by identifying particular autoantibodies.
In a healthy person, antibodies are cells that form part of the body’s immune system. They help to keep the body well by recognising and attacking foreign proteins such as bacteria and viruses.
Autoantibodies, on the other hand, mistakenly attack healthy proteins in the body thinking they are foreign. When autoantibodies are present in the body, the immune system essentially turns its protective function against the body’s tissues.
Testing for different types of autoantibodies can help identify different autoimmune conditions.
Treatment for overlapping conditions involves similar treatment for polymyositis and dermatomyositis on the whole: steroids and immunosuppressants.
Calcium deposits (calcinosis)
Children with juvenile dermatomyositis may develop painful calcium deposits in damaged muscles. These can reduce a child’s mobility and if left untreated can result in the joints becoming permanently bent (known as flexion contracture).
Calcinosis can occur in adults with dermatomyositis, but it is much rarer.
Breathing and swallowing difficulties (dysphagia)
Some people with severe myositis (particularly inclusion body myositis and juvenile dermatomyositis) may experience breathing and swallowing difficulties (dysphagia). This is caused by a weakening of the muscles which control these functions.
There are many different causes of dysphagia, and treatment is guided by the cause.
Interstitial lung disease
Except in inclusion body myositis (IBM), interstitial lung disease (ILD) is the most common and serious complication of the inflammatory muscle diseases.
ILD refers to a group of diseases that affect the tissue and spaces (interstitial) around the air sacs (alveoli) in the lungs.
When these spaces are obstructed by inflammation, the body struggles to exchange the oxygen that is breathed in to the blood stream, and the carbon dioxide that is breathe out.
Symptoms include shortness of breath and a cough. There is a strong association between ILD and myositis antisynthetase syndrome. It is treated with immunosuppressants.
As the heart is a muscle, it too can be subject to the inflammation cause by myositis. The cardiovascular issues people with myositis may experience include cardiomyopathy, arrhythmias, congestive heart failure and atherosclerosis.
All those with myositis should be checked regularly for heart disease, especially if they demonstrate risk factors such as smoking, family history of heart disease, diabetes, high cholesterol and high blood pressure.
Most cases of myositis are treated by suppressing the immune system to prevent the body attacking further healthy structures (such as the muscles).
However, doing so can weaken the immune system’s protection against infection. Those with myositis should do what they can to help prevent infections. This includes exercising good hand washing practices, avoiding others who are sick, avoiding tick and mosquito bites and avoiding food that may carry bacteria.
If symptoms of infection occur, medical care should be sought. Particular infections to look out for include urinary tract infections, respiratory infections, gastrointestinal infection and skin infections.
On rare occasions, myositis can be associated with cancer. Out of the different myositis conditions it affects those with dermatomyositis more often – yet it is still rare. Those with a rapid onset of the disease and poor response to treatment are at higher risk.
The association with cancer is not seen in children and is more common over the age of 40 years.