Juvenile Dermatomyositis (JDM)

Juvenile Dermatomyositis (JDM) is an autoimmune condition which means that the immune system which normally protects the body reacts abnormally and becomes overactive in normal tissues. This immune system reaction leads to inflammation (pain/redness/swelling) which can lead to possible tissue damage. In dermatomyositis, the inflammation affects mainly the small blood vessels in muscle (myositis) and skin (dermatitis). This inflammation may cause muscle weakness or pain and skin rashes particularly on the face, eyelids, knuckles, knees and elbows.

As with most autoimmune diseases the cause of JDM is unknown and it is believed to be multifactorial. Many doctors and researchers across the world are looking at JDM in detail and are trying to find what causes it. There is likely to be a genetic (hereditary) predisposition to all autoimmune diseases and children who have JDM may have a relative who suffers from another autoimmune disease such as diabetes or arthritis.

We know some of the genes (messages that are passed on from parents to children) are more common in children with JDM than children without the disease but these do not explain the whole story. We think autoimmune diseases start due to contact with a ‘trigger’, which makes the body’s immune system overreact. Research has not yet identified one specific trigger but it is thought that triggers could include infection (viruses, bacteria) or an environmental factor (such as sunlight).

The main symptoms of JDM are muscle weakness, muscle pain, skin rashes, tiredness, irritability and fever. Some children can also have joint pains.

Find out more information about JDM symptoms.

JDM can present with a specific pattern of muscle weakness (involvement of muscles in the thighs and upper arms) and specific skin rashes: in these cases JDM is easier to diagnose. Each child is different and your doctor will decide on the best tests for each child. Sometimes JDM can look like other autoimmune disease or like a congenital muscle disease. The tests will help work out which disease your child has.

On physical examination, your doctor will check muscle strength, skin rashes and the blood vessels in the nail beds.

There is no cure for JDM yet, but there are treatment options to help manage the symptoms, control the inflammation and prevent damage from occuring. Early treatment is usually the best predictor of a better outcome of this disease.​

Find out more about the treatment options for JDM

Some children will have just one episode of JDM, which may last for a few years and then goes away (enters what is called ‘remission’). Other children will have disease that comes back after a period of remission.

Some children have a more prolonged disease that can last many years (‘chronic course’). It is important for the disease to be treated by specialists in JDM to provide the best possible result for each patient.

Information on this page has been referenced from the ©Juvenile Dermatomyositis Research Group, who are based at the GOS Institute of Child Health.