Dermatomyositis: definition, symptoms, diagnosis and treatment

By Cristiano Antonino On Apr 11, 2023

Of unknown origin, dermatomyositis is a chronic inflammation of the connective tissues that can affect adults (predominantly female) but also children

Muscle tissue undergoes progressive atrophy, becoming weak and painful, and skin rashes appear on the skin.

In more advanced stages, the disease can affect the internal organs causing serious consequences in the heart, lungs and oesophagus (heart failure, breathing problems, difficulty swallowing).

There is no definitive cure for dermatomyositis, but the disease can be treated with therapies aimed at controlling the symptoms and slowing down its progression.

What is dermatomyositis?

Dermatomyositis is a connective tissue disease of autoimmune origin involving chronic inflammation of the connective tissue.

It is included in the broader group of polymyositis, a heterogeneous group of chronic inflammatory diseases with an autoimmune pathogenesis that affect muscle and skin tissue.

The connective tissues of sufferers of dermatomyositis are inflamed, the patient develops skin rashes and painful muscle symptoms.

The term ‘Dermatomyositis’, in fact, originates from the combination of skin (‘dermato’), muscles (‘my’) and the suffix indicating inflammation (-ite).

In addition to the skeletal muscles (voluntary muscles with intersections on the bones, deputed to movement), the disease can also affect the striated muscles of the heart and the smooth muscles of the respiratory, circulatory and digestive systems.

These are more serious manifestations, which can be life-threatening.

A rare disease, dermatomyositis usually begins around the age of 40-50 (it is more common among women, as with most autoimmune diseases).

However, it can also affect children and adolescents, with onset around 5-15 years of age.

To date, the causes of dermatomyositis are unknown

According to several scholars, viral or bacterial infections play a decisive role.

But several experts consider this condition to be a symptom of other autoimmune diseases such as:

Sjögren’s syndrome, a disease that causes dry eyes, mouth and mucous membranes;
rheumatoid arthritis, a chronic inflammatory disease that mainly affects the joints but can also affect the kidneys and lungs;
systemic lupus erythematosus, a connective tissue disease with erythematous manifestations on the mucous membranes and skin;
autoimmune vasculitis, caused by the immune system’s attack on blood vessels.

Its prevalence is unknown. According to the most authoritative studies, it affects 1-12 out of every 1,000,000 people each year.

Symptoms

Early detection of dermatomyositis is not easy.

The first symptom one feels, muscle weakness, is in fact common to many other diseases, being rather non-specific.

The most common symptoms are:

Muscle weakness, especially in the proximal muscles (neck, shoulders, hips and thighs). Initially, the patient realises that something is wrong because he/she has difficulty performing simple movements: crossing his/her legs, combing his/her hair, climbing stairs, standing up. In the course of weeks and months, the weakness spreads and can reach the muscles of the neck, and those involved in chewing, breathing, phonation and swallowing;
myalgia, pain in the contracting muscles;
muscle soreness;
muscle atrophy: the mass or tone of muscles is reduced, and the person has difficulty in performing even very simple actions;
skin manifestations: found in 25% of cases, they take the form of a heliotrope rash. The upper eyelids take on a purplish tinge (often associated with oedema) and purplish or erythematous papules or plaques may appear above the bony protrusions (especially on the hands, knees, elbows and malleoli). Skin manifestations, photosensitive and sometimes scaling, may also affect the face and neck and resemble the rash of systemic lupus erythematosus or seborrhoeic dermatitis;
vasculitic manifestations: especially in children, inflammation of small blood vessels may be present and nodules, erythema and periungual lesions may appear;
cutaneous calcinosis: also more frequent in children, it consists of the formation of hard subcutaneous nodules at the fascias lining the muscles of the limbs. If the indurations tear, calcareous material may leak from the skin;
Raynaud’s phenomenon, reported in 35% of patients: hands and feet (but also nose and ears) become cold, numb and change colour after being exposed to cold.

More serious symptoms of dermatomyositis are:

respiratory problems: if the pathology attacks the intercostal muscles, which are responsible for breathing control, the patient experiences difficulty breathing;
cardiac problems: in the event of inflammation of the myocardium, arrhythmias may occur and heart failure may develop
difficulty swallowing: when the smooth musculature of the digestive system undergoes changes, the patient suffers from dysphagia and – consequently – from problems resulting from malnutrition. This predisposes to the development of ab ingestis pneumonia, an inflammation of the lungs caused by foreign substances (usually food residues) entering the bronchopulmonary tree.

Dermatomyositis is particularly complicated to manage when it occurs in association with other diseases.

Very often, the patient also suffers from Raynaud’s syndrome or pulmonary interstitiopathy (alteration of the tissue lining the pulmonary alveoli, which can lead to pulmonary fibrosis).

Diagnosis

Being characterised by the association of skin eruptions and muscular problems, dermatomyositis is not a difficult condition to diagnose.

The diagnosis is essentially based on an objective examination, with the patient presenting his or her symptoms and the doctor testing the family and clinical history.

The specialist then analyses the skin eruptions, palpates the muscles to check their consistency, which is softer to the touch than the physiological situation.

He will then prescribe tests to confirm the diagnosis or provide a clearer picture of the situation.

First of all, the patient should have blood tests to measure the levels of creatine kinase, aldolase, auto-antibodies and tumour antigens, which will be higher than normal.

The area affected by the skin rash will then be biopsied, as well as muscle cells taken from the painful areas.

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If necessary, further tests may be useful: electromyography to assess muscular electrical activity, magnetic resonance imaging to view the muscle mass, and chest X-rays to investigate the health of the lungs.

Treatment

There is no specific cure for dermatomyositis: all currently available treatments only serve to alleviate the symptoms and slow down the progress of the disease.

If diagnosed early, drug therapy can have satisfactory effects and improve the patient’s quality of life.

The most commonly used drugs are corticosteroids, due to their anti-inflammatory capacity, and immunosuppressants, which reduce the immune response.

If the patient does not show improvement, immunoglobulins can be administered intravenously.

These therapies are not without side effects: immunosuppressants increase the risk of infection, while corticosteroids expose patients to diseases such as diabetes and hypertension.

Very often, patients with dermatomyositis may need physiotherapy to maintain muscle tone, therapy with a speech therapist if they suffer from swallowing disorders, and the intervention of a dietician so that they can learn to take in all the nutrients they need to cope with the condition.

Surgery is reserved for cases with calcinosis, to remove calcium deposits emerging from the skin.

Those diagnosed with dermatomyositis must protect the skin, affected by the skin rash, from the sun.

They must also work on muscle tone by doing adequate physical activity, rest when they feel excessively tired, and not be afraid to talk about their condition (possibly seeking the help of a specialist).

Currently, the prognosis of those suffering from dermatomyositis is much improved.

With early intervention, the survival rate ten years after diagnosis is 57%.

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