Juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is an autoimmune condition that affects multiple systems in the body, although it mainly causes muscle weakness and a skin rash that starts in childhood.

Juvenile dermatomyositis is a type of myositis – a group of conditions that cause muscle inflammation and progressive weakness. These conditions are also known as idiopathic inflammatory myopathies. Juvenile dermatomyositis is different to adult dermatomyositis – information about adult dermatomyositis can be found on our dermatomyositis page.

JDM is the most common form of juvenile idiopathic inflammatory myositis (JIIM) although there are other subtypes, including juvenile-onset immune-mediated necrotising myopathy, overlap myositis, juvenile polymyositis and juvenile anti-synthetase syndrome.

Skin rash

A skin rash is a common symptom of JDM. A patchy red or purple rash may typically appear on the eyelids, face, neck, back of the shoulders, front of the chest, or on the backs of the hands and fingers. Some forms of JDM can cause ulcers. Rashes may be faint or look different on different skin tones. The affected areas can be itchy, painful, and may also swell. In severe cases, the fat underneath the skin can also be affected and become thinner or harder (lipodystrophy). Exposure to sunlight can make the rash worse.

Muscle weakness

People with JDM can experience muscle weakness, usually affecting the muscles closest to the centre of the body (proximal muscles) such as those in the torso, shoulders, upper arms, thighs, and buttocks. Muscle weakness develops gradually and may only be 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. Walking and running can also become challenging and more tiring than usual.

People with JDM may have difficulty swallowing (dysphagia) or develop changes in their voice if the oesophageal muscles are affected. Breathing problems can also occur if the chest muscles are affected.

Calcium deposits

Some people can develop small, hard calcium deposit lumps under their skin or in their muscles. This is called calcinosis. If the muscles become inflamed and calcium builds up, the muscles can shorten and become tight. This may stop some joints from fully straightening (contractures).

Respiratory

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

Gastrointestinal

Apart from swallowing difficulties (dysphagia) which can occur when the oesophageal muscles are affected by JDM, other parts of the gut can also be involved. People with JDM may have changes in the way the intestines move or swelling of the intestines. This can result in stomach pain, vomiting, diarrhoea, or problems with absorbing nutrients from food.

Pain

Some people may experience muscle pain. This can cause aching, discomfort, or mild tenderness of the affected muscles. Joint pain and swelling may also occur.

Fatigue

People with JDM can experience fatigue as exercise and movement becomes increasingly difficult. They may need to rest more often and may struggle to keep up with others their age. They may also become more irritable.

Growth and development

The effects of inflammation and muscle weakness in JDM can cause delays to growth and development in children. When JDM is active, children may not grow as much as expected, or they may reach puberty later than expected.

The cause of JDM 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.

JDM 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.

JDM 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, or sometimes a muscle biopsy where a small sample of muscle is taken and examined under a microscope. In some cases, CT scans of the chest may also be needed.

Blood tests look for elevated levels of creatine kinase (CK), a marker released by damaged muscle, and to identify specific antibodies associated with myositis. JDM can present with a characteristic pattern of muscle weakness and specific skin rashes which can make it easier to diagnose.

For more information, see our diagnosis page.

Access to a healthcare team

It’s important to have access to a specialist team who can assess symptoms 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. Ask your GP if you do not have contact with a specialist doctor.

Medications

JDM is managed in a similar way to adult dermatomyositis, however dosages are based on body weight. Typically, the sooner treatment begins following onset, the better the outcome.

• Creams and ointments – If skin rash is the main issue, steroid or tacrolimus creams may be prescribed to apply to the skin.
• Steroids – JDM 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 their improvement in symptoms. Not all people with JDM require steroids and if the condition is mild, disease-modifying anti-rheumatic drugs alone may be enough. In the long term, steroids can cause side effects such as an increased risk of infections, fragile skin which bruises easily, weight gain, diabetes and weakening of the 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 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 the long-term management of JDM. These medications 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 for 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 infliximab and rituximab, may be used. They are delivered through intravenous infusion (IV). Biological treatments can only be prescribed by a specialist.
• Immunoglobulins (IVIG) – IVIG is another option for people with severe JDM. It’s an infusion usually given over three to five days. The infusion contains antibodies extracted from donated blood.

Exercise and physiotherapy

Physiotherapy is beneficial for people with JDM and can help maintain muscle strength, prevent tightening of muscles and joints (contractures), and support a healthy heart. A physiotherapist is a healthcare professional who helps manage symptoms through movement, exercise, and manual therapy. They can put together a suitable exercise routine to follow. Children will need support from caregivers to guide them through exercises and provide encouragement. For advice for adults, see exercising with a muscle wasting condition.

Occupational therapy

In some cases, occupational therapists can help with aids or equipment that assist for certain actions or activities, particularly when muscle weakness or contractures are present.