What is dermatomyositis?

Dermatomyositis is a rare but treatable autoimmune condition. It causes inflammation in the skin, muscles and blood vessels. This often leads to a rash and muscle weakness. It can also affect your lungs.

Dermatomyositis can affect any age group, but it is more likely to occur in middle-aged adults. Juvenile dermatomyositis (JDM) usually affects children between 4 and 10 years old, but it can happen at any age. Dermatomyositis in adults and JDM share the same key features. The complications and features of this disease vary a lot between these 2 groups.

Dermatomyositis is more common in females. It is not passed down from parent to child and cannot spread from person to person.

What are the symptoms of dermatomyositis?

The main symptoms of dermatomyositis include skin rashes and muscle weakness. These symptoms develop gradually. Each person can experience them differently.

Skin rashes

Dermatomyositis often causes skin rashes. They show up usually before or along with the muscle weakness.

Common rashes caused by dermatomyositis or JDM include:

• redness on your face, or rash and swelling on the eyelids
• flat, red areas on your upper back, shoulders or neck
• discoloured bumpy, or scaly patches on your elbows, knees, ankles and knuckles
• reddish-brown skin colouring on your thighs and buttocks
• red or dark skin around your fingernails or cracks in the skin of the fingers
• scaly, itchy, dry patches on your scalp

These rashes get worse with sunlight and may feel dry or rough.

Muscle weakness

Muscle weakness usually begins in your hips, thighs, upper arms and shoulders. It worsens over time. It can make daily activities difficult.

Muscle pain and tenderness are also common.

Other symptoms

Other symptoms may include:

• joint pain and swelling
• calcinosis — hard lumps full of calcium that build up under the skin, in muscles or tendons
• fever
• tiredness

What causes dermatomyositis?

Doctors don't know the exact cause of dermatomyositis. It happens when the immune system, which normally protects the body, attacks blood vessels in the muscles and skin.

Some experts think that cancer, viruses or certain medicines may trigger it. While dermatomyositis isn't passed down from parent to child, genetic factors may increase your chance of being affected.

When should I see my doctor?

You should see your doctor if you notice symptoms of dermatomyositis. Early diagnosis helps manage the condition and prevent complications.

If you're diagnosed with dermatomyositis and have trouble breathing, seek emergency help immediately. Regular doctor visits are also important to check and adjust your treatment.

How is dermatomyositis diagnosed?

To diagnose dermatomyositis, your doctor will ask about your medical history and do a physical exam. They may refer you to a rheumatologist (a specialist for joints and muscles). Several tests may help confirm the diagnosis, including:

• a physical check-up
• blood tests to check for muscle damage
• MRI scans to look at your muscles
• electromyography (EMG). which measures your muscle's response to nerve stimulation
• a biopsy, where doctors take a small tissue sample for testing
• nerve conduction tests to check how fast nerves send signals

Your doctor will decide which tests you need based on your or your child's symptoms.

How is dermatomyositis treated?

Treatment for dermatomyositis will include medicines that help control inflammation and ease your symptoms. Treatment plans vary for each person. The goal is to reduce muscle weakness and prevent complications.

Common treatments with medicines include:

• steroids — corticosteroids like prednisolone to reduce inflammation
• immunosuppressants — medicines that affect the immune system and reduce inflammation
• intravenous immunoglobulin therapy (IVIg) — an infusion of antibodies

Other treatments may include:

• physiotherapy — to strengthen muscles
• speech therapy — for swallowing difficulties to avoid choking
• surgery — may be necessary for wounds or sores

Living with dermatomyositis

Living well with dermatomyositis means managing symptoms while maintaining a healthy lifestyle. Early detection and constant care are important to minimise complications.

Here are some tips that may help you:

• Have regular check-ups — your doctor will check for issues like muscle strength, breathing and heart function. You may also need cancer screenings, especially in the first 5 years after diagnosis.
• Supplements — ask your doctor if supplements like calcium and vitamin D can help prevent brittle bones in your situation. Steroids can increase your risk of osteoporosis.
• Exercise and physiotherapy — these can help you maintain your flexibility and strength.
• Mobility aids — some people may need a cane or a wheelchair during flare-ups. An occupational therapist or physiotherapist can help you arrange these.
• Maintain a balanced diet — especially when you are taking steroids as they can lead to weight gain.
• Sun protection — use sunscreen and protective clothing to prevent skin rashes from worsening.

Children with dermatomyositis

Treatment of dermatomyositis will usually improve symptoms in children. It may get better by the time your child is an adult.

Other tips for children include:

• Regular check-ups — your child may need frequent blood tests and doctor visits.
• Activities and exercise — exercises will help your child join in regular activities like playing, sport and school. Continue physiotherapy at home to help with progress.
• School involvement — inform your child's schools about their condition, so they can adjust activities.

What are the complications of dermatomyositis?

Dermatomyositis can lead to various complications that affect different parts of your body. Over time, muscles can weaken (atrophy) and shorten (contracture).

Other complications may include:

• Calcinosis — hard, painful lumps of calcium under the skin that may cause sores.
• Lung disease — scarring in the lungs can make breathing difficult, this can be life-threatening.
• Muscle weakness — this may affect your ability to swallow, speak, or hold your head up.
• Difficulty swallowing — this may lead to malnutrition and an infection in your lungs.
• Heart issues — such as inflammation of the heart muscle and risk of heart attacks.
• Higher cancer risk — such as lung, breast, prostate, or ovarian cancer.

Can dermatomyositis be prevented?

You can't prevent dermatomyositis, as its exact cause is not well understood. Early diagnosis and treatment can help manage symptoms and complications.

Resources and support

• The Sydney Children's Hospitals Network has information on dermatomyositis for parents and carers.
• Visit the Australian Physiotherapy Association to find a physiotherapist.
• Visit Speech Pathology Australia to find a speech therapist.
• NDIS provides information for people living with disabilities.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

Looking for information for Aboriginal and/or Torres Strait Islander people?

• North West Hospital and Health Service offers the First Nations Healthy Skin Program.
• Find an Aboriginal Community Controlled Health Organisation (ACCHO) or Affiliate near you.