Dermatomyositis (DM)

Dermatomyositis (DM) is an autoimmune condition that causes muscle weakness, inflammation, and a skin rash. It can affect people of any age. There are some forms of dermatomyositis that do not affect the muscles much – or at all. A skin rash is a key feature of the condition, and some people may have lung problems.

The type of dermatomyositis that affects children is known as juvenile dermatomyositis, and can have some differences.

Dermatomyositis is a type of myositis – a group of conditions that cause muscle inflammation and weakness. These conditions are also known as idiopathic inflammatory myopathies.

Skin rash

Dermatomyositis affects the skin, which makes it distinct from other types of myositis. A patchy red or purple rash may typically appear on the eyelids, face, neck, chest, back of the shoulders, or on the backs of the hands and fingers. Some forms of dermatomyositis can also cause ulcers. Rashes may look different on different skin tones and can be itchy, painful, and may also swell. Exposure to sunlight can make the rash worse.

Muscle weakness

People with dermatomyositis can experience muscle weakness, which usually affects the muscles in the torso, shoulders, upper arms, thighs, and buttocks. Muscle weakness usually develops slowly and may become noticeable after a few weeks or months. Those affected may find it hard to stand from a seated position or from the floor, climb stairs, or raise their arms above their head.

They may also have some difficulty swallowing (dysphagia) if the oesophageal (food pipe) muscles are affected, or breathing problems if the chest muscles are affected. The heart muscle can also be affected. This can cause abnormalities in the heartbeat or reduce the heart’s ability to pump.

Respiratory

Inflammation of the lungs can happen in some forms of dermatomyositis. People may notice a dry, irritating cough or that they become breathless while doing activities or exercises that they were previously able to do easily. If untreated, lung inflammation can progress to scarring (fibrosis). In some cases, lung inflammation progresses quickly and can become life-threatening.

Pain

Some people may experience muscle pain, especially if symptoms start quickly. This can cause aching, discomfort, or mild tenderness in the affected muscles. Joint pain and swelling may also occur.

The cause of dermatomyositis is unclear, but it’s believed to be an autoimmune condition. This means the immune system, which normally protects the body, mistakenly attacks healthy tissues.

Dermatomyositis is typically not considered to be an inherited condition, but some people may inherit genes that make them more likely to develop an autoimmune condition.

Dermatomyositis is usually diagnosed by a specialist, using a clinical examination and one or more tests. This may include blood tests, a magnetic resonance imaging (MRI) scan, an electromyography (EMG) test, CT scans of the lungs, or sometimes a skin or muscle biopsy. A blood test can look for high levels of creatine kinase (CK), which is a sign of muscle damage, and identify specific antibodies associated with dermatomyositis.

For more information, see our diagnosis page.

Access to a healthcare team

People with dermatomyositis should have access to a specialist team to assess their condition and discuss treatment. Usually, the lead professional will be a neurologist in a specialist neuromuscular clinic, or a rheumatologist. A neurologist is a doctor who specialises in conditions that affect the muscles and nervous system, and a rheumatologist is a doctor who specialises in inflammatory conditions that affect the joints and muscles. If there isn’t much muscle involvement, sometimes a dermatologist will lead the care team instead. A dermatologist is a doctor who specialises in skin conditions. If you’re not in contact with a specialist doctor, speak to your GP about getting access to one.

Medications

• Creams and ointments – If skin rash is the main issue, steroid or tacrolimus creams may be prescribed to apply to the skin.
• Steroids – Dermatomyositis is often first treated using corticosteroid tablets, such as prednisolone. Steroids reduce the activity of the immune system. Prednisolone is usually started at a high dose and can be given as tablets, injection, or by infusion. The dose is then gradually lowered based on the person’s response and improvement in symptoms. Not everyone with dermatomyositis needs steroids and if the condition is mild, disease-modifying anti-rheumatic drugs (DMARDs) alone may be enough. In the long term, steroids can cause side effects such as increased risk of infections, high blood pressure, fragile skin which bruises easily, weight gain, cataracts, and weakened bones (osteoporosis). Regular monitoring and additional medications can help manage these risks but the best way to avoid side effects is to gradually reduce the dose, aiming to eventually come off steroid treatment or to take the lowest required dose. Do not stop taking steroids suddenly, as this is dangerous and has serious health risks. It’s important to carry a Steroid Emergency Card, as it provides important information for healthcare professionals in an emergency. The card can be obtained from a GP, community pharmacy, or specialist hospital team.
• Disease-modifying anti-rheumatic drugs (DMARDs) – DMARDs, such as methotrexate, azathioprine, and mycophenolate are used for long-term management of dermatomyositis. These drugs also reduce the activity of the immune system and are generally safer than long-term steroid use. However, they can take weeks to months to start working effectively, which is why steroids may be needed at first. DMARDs require regular blood tests to monitor side effects and to make sure the treatment is working effectively.
• Biological treatments – In severe cases where symptoms don’t improve with steroids and traditional DMARDs, biological therapies, such as rituximab (through intravenous infusion) or abatacept (through subcutaneous injection or intravenous infusion), may be used. Biological treatments target more specific parts of the immune system than DMARDs. Biological treatments can only be prescribed by a specialist.
• Immunoglobulins (IVIG) – IVIG is another option for people with severe dermatomyositis. It is an infusion usually given over three to five days. The infusion contains antibodies extracted from donated blood.

Exercise and physiotherapy

Regular exercise is highly recommended for people with dermatomyositis. Exercise can help improve wellbeing, maintain muscle strength, and support a healthy heart. A physiotherapist is a healthcare professional who helps manage symptoms through movement, exercise, and manual therapy. They can assess a person’s needs and put together a suitable exercise plan. It’s important to exercise safely and allow time to fully recover before doing more exercise. For advice for adults, see exercising with a muscle wasting condition.

Sun protection

Sunlight and ultraviolet (UV) light can make the rash from dermatomyositis worse, so it’s important people with dermatomyositis protect themselves from the sun. This includes wearing hats, protective clothing, and using sun cream with a high SPF.