Overview

Juvenile dermatomyositis (JDM) is a rare, complex, and potentially life-threatening disease that often starts in childhood and is characterised by muscle weakness and distinctive skin rashes. It is an autoimmune condition where the immune system, designed to protect the body, becomes overactive in normal tissues, resulting in inflammation marked by pain, redness, and swelling.¹ This immune response primarily targets small blood vessels in muscles (myositis) and skin (dermatitis).

The exact origin of JDM remains unclear, but it is thought to be linked to blood vessel issues in muscles and other organs, especially in genetically susceptible children, potentially triggered by environmental factors.² Treatment primarily addresses muscle inflammation and aims to prevent complications like contractures (muscle stiffness) and calcinosis (calcium deposits).

As the predominant idiopathic inflammatory myopathy in childhood, constituting 80% or more of cases, JDM takes precedence among various inflammatory muscle conditions in children.³ Early intervention is crucial for better outcomes, as delayed treatment may lead to a more challenging disease course and diminished quality of life. Hence, understanding JDM is vital not only for healthcare providers and researchers but also for parents and the general public. This article seeks to elucidate the fundamental aspects of this condition, offering clarity and insight to enhance awareness.

Causes of juvenile dermatomyositis

The exact cause of juvenile dermatomyositis (JDM) remains elusive, but it is believed to result from a complex interplay of genetic susceptibility and environmental triggers.¹

• Genetic Predisposition: JDM exhibits a familial tendency in certain cases, suggesting a potential genetic predisposition. Specific gene variants are more prevalent in children with JDM
• Abnormal Immune Response: The immune system misidentifies normal muscle and skin proteins as foreign, initiating an autoimmune attack. This process leads to persistent inflammation and tissue damage
• Environmental Factors: Various environmental elements are implicated in JDM development. Infectious agents such as specific viruses and bacteria, along with triggers like sun exposure, medications, and vaccines, are believed to contribute to the initiation of JDM

Signs and symptoms of juvenile dermatomyositis

The main signs and symptoms of JDM include:⁴

• Skin rash: A distinctive reddish or purplish rash often appears early on the eyelids, cheeks, and knuckles. The rash may precede muscle weakness. Other skin changes include thickening and scaliness. The capillaries around the nails may become enlarged and visible
• Muscle weakness and fatigue: Pronounced muscle weakness in areas such as the neck, shoulders, abdomen, hips, and upper legs. Progressive weakness of the skeletal muscles and difficulty moving the arms, legs, neck, or face are common early symptoms. Weakness is generally symmetrical, affecting both sides of the body. It gets worse over weeks to months. Everyday tasks like climbing stairs or rising from a chair become challenging. Persistent tiredness and difficulty participating in physical activities are common
• Gastrointestinal involvement: Difficulty in swallowing can happen due to muscle inflammation affecting the oesophagus. This increases the risk of choking or aspiration pneumonia. There can be ulcerations in the stomach, leading to poor absorption of nutrients and oral medications
• Calcinosis: Development of firm, pebble-like calcium deposits beneath the skin, typically in areas prone to pressure. These deposits can induce pain and interfere with muscle movement. In more severe cases, these calcium deposits may break through the skin, creating openings that pose a risk of infection
• Joint pain: Some children have mild joint inflammation or pain

Other possible signs and symptoms include fevers, irritability, abdominal pain, diarrhoea, and weight loss. Symptoms and their severity can vary greatly between individual children with JDM.⁴

Management and treatment for juvenile dermatomyositis

Treatment for JDM aims to manage symptoms and improve the quality of life for affected children. Although there's no cure, with appropriate care, many children achieve remission and lead active lives with minimal complications. The primary treatment goals include enhancing muscle strength, relieving pain and skin rashes, managing complications, and preventing disease progression.⁵ The treatment approach typically involves a combination of interventions:

• Corticosteroids: High-dose oral corticosteroids, such as prednisolone, are commonly used initially to control inflammation and enhance muscle strength. Once the disease is stabilised, the dosage is gradually reduced to the lowest effective level¹
• Disease-modifying antirheumatic drugs (DMARDs): Medications like methotrexate are often prescribed alongside steroids to facilitate lower steroid doses. Other DMARDs, including azathioprine, mycophenolate mofetil, and cyclosporine, may also be utilised
• Intravenous immunoglobulin (IVIG): IVIG helps regulate the immune system and might be employed short-term during disease flares or in severe cases that don't respond well to corticosteroids or DMARDs
• Physical and occupational therapy: These therapies involve exercises to maintain or restore musculoskeletal function, including stretching and strengthening exercises
• Topical skin treatments: Moisturisers, topical steroids, and topical tacrolimus are used to manage skin rashes and calcinosis lesions
• Sunscreen: Due to heightened sensitivity to UV damage, sun protection is crucial

In cases where standard treatments prove ineffective, other immunosuppressants or biologic medications may be considered under close medical supervision. Comprehensive care involving various specialities, including rheumatology, dermatology, rehabilitation medicine, and ophthalmology, ensures a holistic approach to managing JDM.⁵

Diagnosis

JDM is diagnosed based on presenting symptoms, physical examination findings, and test results. There is no single definitive test for JDM. Key aspects of the diagnosis process may include:⁶

• Medical history and physical examination to assess symptoms and look for characteristic rashes and muscle weakness patterns
• Blood tests detect elevated muscle enzymes like creatine kinase, aldolase, lactate dehydrogenase, and aspartate transaminase. These indicate muscle inflammation
• Additional blood tests include anti-nuclear antibody (ANA), anti-Jo-1, and other autoantibodies.
• Electromyography to assess muscle electrical activity
• Muscle biopsy of an affected area, which reveals muscle fibre damage and inflammation under the microscope
• MRI scans to evaluate muscle inflammation and damage
• Skin biopsy to examine skin changes microscopically

Since JDM symptoms can resemble other conditions, physicians must rule out similar disorders like polymyositis, muscular dystrophy, and psoriasis.⁷ Prompt, accurate diagnosis allows early treatment to preserve muscle function and prevent complications.

Complications

Without proper treatment, juvenile dermatomyositis can lead to several potentially serious complications:⁸

• Muscle atrophy and contractures: Due to persistent inflammation, the muscles may waste away and tighten, leading to restricted mobility of affected areas
• Dysphagia and aspiration: Difficulty swallowing increases the risk of food/liquid entering the lungs, causing aspiration pneumonia
• Interstitial lung disease: Scarring of lung tissue impairs breathing function
• Osteoporosis: Chronic inflammation and steroid treatment may weaken bones
• Growth impairment: JDM and steroid use can affect growth and puberty
• Skin ulceration and necrosis: Severe skin inflammation can cause painful sores and tissue death
• Lipodystrophy: Loss of fat layers under the skin causes an emaciated appearance
• Cardiac issues: The heart muscle or conduction can be affected, rarely

With early, aggressive treatment, most of these complications can be avoided or minimised. However, even well-managed JDM may leave some residual muscle weakness, contractures, and calcinosis.

Prognosis

The course of the disease is unpredictable, and outcomes vary among individuals. Some cases may have a single episode (monocyclic), others might involve multiple cycles (polycyclic), and some cases may persist over the long term (chronic). The prognosis is best when JDM is diagnosed and treated early before extensive muscle damage occurs. Aggressive multidisciplinary treatment tailored to the individual child also improves outlook. Nonetheless, in developing nations, there remains a high rate of mortality. 

The primary causes of death typically include profound muscle weakness, additional severe infections, inflammation of the gastrointestinal blood vessels with a potential for bowel perforation, heart failure, and respiratory distress.⁷

However, the prognosis for children with juvenile dermatomyositis has improved significantly in recent decades, thanks to earlier diagnosis and better treatments. Before the 1990s, up to one-third of children with JDM died due to complications of the disease itself or adverse effects of treatment. With current medical care, the 10-year survival rate exceeds 95%. Most children achieve remission, where symptoms are minimal or absent when on treatment.⁷ Around 20-40% may experience one or more disease flares, requiring temporary intensification of therapy. While remission is possible, some residual muscle weakness often remains. Ongoing follow-up care is essential even after remission.

FAQs

How can I prevent juvenile dermatomyositis?

There are no known ways to prevent JDM since the cause is not fully understood. Focus on getting an early evaluation for any suggestive symptoms in children, like muscle weakness, skin changes, or delayed motor skills development. Prompt treatment can improve outcomes.

How common is juvenile dermatomyositis?

JDM is very rare, affecting about 3 to 4 children out of every million per year. It can occur at any age but most commonly appears between the ages of 5 and 15 years. Young people assigned female at birth (AFAB) are affected more often than young people assigned male at birth (AMAB).⁴

Who is at risk of juvenile dermatomyositis?

While JDM is rare overall, specific factors can elevate the risk, including a family history of autoimmune conditions, exposure to potential viral triggers, and possessing certain human leukocyte antigen (HLA) gene types associated with increased susceptibility. If there are specific concerns or a family history, consulting with a healthcare professional can provide personalized insights and guidance.

When should I see a doctor?

If you observe persistent signs like muscle weakness, skin rashes, or ongoing fatigue in your child, it's wise to promptly seek guidance from a healthcare professional. Timely identification and action play a vital role in addressing JDM. If there's a family history of autoimmune conditions or other potential risk elements, consulting a doctor for a comprehensive assessment is advisable.

Summary

Juvenile dermatomyositis (JDM) is a rare autoimmune disease causing muscle inflammation and weakness, along with distinctive skin rashes in children and youth. Though the exact cause is unknown, it likely involves genetics and environmental triggers. Early diagnosis and treatment with medications, therapy, and sun protection can help control symptoms long-term. Ongoing research is underway to understand JDM better and improve care. With comprehensive treatment, most children with JDM can live active, fulfilling lives.