Medicines for Myositis

What it is

Myositis is a general term for inflammation of the muscles. It most often refers to a group of uncommon conditions (the inflammatory myopathies) in which the body’s immune system mistakenly attacks the muscles, causing inflammation, muscle weakness, and sometimes other symptoms. The main types include polymyositis (affecting muscles), dermatomyositis (which affects muscles and also causes a characteristic skin rash), and inclusion body myositis (which tends to affect older adults), among others; a form also occurs in children (juvenile dermatomyositis). The hallmark of myositis is muscle weakness, which typically develops over weeks to months and often affects the muscles closer to the centre of the body (such as the shoulders, upper arms, hips, thighs, and neck) — leading to difficulty with activities such as climbing stairs, getting up from a chair, lifting the arms (for example to wash hair), or, in some cases, swallowing. There may also be muscle aching or tenderness (though pain is not always prominent), tiredness, and, in dermatomyositis, a distinctive skin rash (such as a rash on the face, eyelids, knuckles, or elsewhere). Some types can be associated with other problems, such as effects on the lungs or, in some cases, links with other conditions. Myositis is uncommon, and because muscle weakness and tiredness can have many causes, it is diagnosed through assessment and tests (such as blood tests, muscle tests, imaging, and sometimes a muscle biopsy). The important and encouraging point is that most types of myositis are treatable: because the inflammation is driven by the immune system, treatment usually involves medicines that reduce the inflammation and calm the immune system (such as steroids and other immune-modulating medicines), which can control the disease and improve the muscle weakness, along with physiotherapy and support. (Inclusion body myositis responds less well to these medicines and is managed differently, with a focus on maintaining function.) The key messages are that myositis is inflammation of the muscles (usually immune-driven) causing muscle weakness, that it is uncommon and diagnosed with tests, and that most types are treatable with medicines that calm the immune system, along with physiotherapy.

How it is treated

Myositis is diagnosed and treated by specialists (such as rheumatologists or neurologists), and most types are treated with medicines that reduce the inflammation and calm the immune system, along with physiotherapy and support. Because muscle weakness and tiredness have many causes, reaching a diagnosis involves assessment and tests, which may include blood tests (such as markers of muscle inflammation), tests of the muscles and nerves, imaging (such as MRI), and often a muscle biopsy (taking a small sample of muscle), along with checking for the skin features of dermatomyositis and for any associated problems (such as effects on the lungs, or other conditions). Once diagnosed, treatment of the immune-driven types of myositis focuses on reducing the inflammation and controlling the immune system’s attack on the muscles: this usually starts with steroids (corticosteroids) to bring the inflammation under control, often alongside other medicines that calm the immune system (disease-modifying/immunosuppressant medicines), which help control the disease and allow the steroid dose to be reduced over time; for more resistant or severe disease, other treatments, including certain targeted or biologic therapies, may be used. Treatment is tailored to the type of myositis and the individual, and aims to improve the muscle strength, control the disease, and manage any associated problems. Alongside medicines, physiotherapy and exercise are important to maintain and improve muscle strength and function (guided appropriately), and support with daily activities, swallowing (if affected), and general wellbeing is provided as needed. Monitoring the disease and the treatment, and managing side effects, are part of ongoing care. Inclusion body myositis is an exception in that it responds less well to immune-calming medicines, so its management focuses more on maintaining function, physiotherapy, and support. Because myositis can be associated with other conditions or complications, these are checked for and managed. With treatment, many people with the treatable types of myositis improve, though the condition and its treatment need ongoing management, and outcomes vary with the type. The reassuring messages are that myositis, although uncommon and sometimes causing significant weakness, is (for most types) treatable — with medicines that calm the immune system controlling the inflammation and improving muscle strength, alongside physiotherapy and support — and that specialist care guides treatment; so muscle weakness that is developing or unexplained should be assessed.