Juvenile Myositis - Causes, Symptoms, and Treatment

Introduction:

Juvenile myositis (JM) is one of the conditions in a group of juvenile polymyositis (JPM) and juvenile dermatomyositis (JDM). These are rare autoimmune diseases in which the immune system of the body attacks its cells and tissues. These conditions are characterized by muscle damage caused by the inflammatory process of the blood vessels that lie under the skin and muscles. Juvenile myositis affects every child differently. It can range from mild to severe.

Myositis means inflammation of the muscles of the body that are used in the movement of the body. It usually affects children of age 2 to 15 years. In the case of juvenile dermatomyositis, the child may have difficulty swallowing and breathing, and the heart may also get affected. Juvenile polymyositis is extremely rare and can cause muscle weakness without skin rashes.

What Are the Types of Juvenile Myositis?

The most common type of juvenile myositis is juvenile dermatomyositis (JDM). However, juvenile polymyositis (JPM) is very rare. Other than these, viral myositis, a type of benign acute childhood myositis, can also affect children.

• Juvenile Dermatomyositis - This is characterized by inflammation of muscles leading to weakness and may also affect the blood vessels. This condition affects three out of one million children each year. This condition is mostly seen in children aged five to ten, and girls get affected twice as compared to boys.

• Juvenile Polymyositis - This condition is also characterized by muscle inflammation leading to weakness. However, it may affect multiple body systems, including the heart, lungs, and digestive systems. It is rare, accounts for less than five percent of incidences, and usually develops in early childhood, affecting girls more commonly.

• Benign Acute Childhood Myositis - It usually affects school-age children and is commonly seen in children recovering from flu or another respiratory infection. The incidence rate of this condition is 2.6 cases per 100,000 children.

What Is the Incidence Rate of Juvenile Myositis?

Juvenile myositis is rare, and the exact incidence rate is unknown. Approximately two to four children in a million are diagnosed yearly in the United States. It usually begins in childhood to the teen years, and the average onset of this disease is found to be in between six to seven years old children. Twenty-five percent of children are found to be of age four or less. This is most commonly seen in girls twice as compared to boys.

What Is the Pathogenesis of Juvenile Myositis?

The immune system of the body is a group of cells that protects the body from various infections. In an autoimmune disease such as juvenile myositis, the immune system gets activated but does not shut off after eliminating the harmful disease-causing foreign particles. It starts attacking the healthy tissues of the body, harming the body instead of protecting it.

This action of the immune system causes inflammation in the blood vessels under the skin and the muscles, which leads to weak muscles and skin rashes. As it progresses, it can cause inflammation in other body systems, such as the digestive tract, heart, and lungs.

What Are the Causes of Juvenile Myositis?

Various research studies believe environmental and genetic factors can contribute to juvenile myositis. This disease can be found in children with a family history of autoimmune diseases like thyroid disorder, rheumatoid arthritis (chronic inflammatory disorder affecting multiple joints in the body), and diabetes (disease-causing too much sugar in the blood). In some cases, viral or bacterial infection can also trigger an immune response that causes the body to attack itself. Other environmental factors, such as heavy exposure to the sun, may also lead to this condition.

What Are the Signs and Symptoms of Juvenile Myositis?

The symptoms of juvenile myositis vary by type, which includes the following:

1. Juvenile Dermatomyositis:

In the initial stage, Juvenile dermatomyositis may cause some or all of the following symptoms in children:

• Fatigue.

• Fever.

• Gottron’s papules or Gottron’s sign (bumps found over the knuckles, elbows, and knees).

• Characteristic reddish-purple heliotrope rash (purplish rash around the eyes).

• Loss of appetite.

• Weight loss.

• Digestive issues.

• Joint pain.

• Contractures (stiffening of the joint, causing it to shorten and stay bent).

• Trouble in daily activities like climbing stairs, standing from a sitting position and getting dressed.

• Choking while eating or drinking.

• Muscle tenderness.

• Lipodystrophy (complete or partial loss of fat tissue).

• Weak or painful muscles.

• Calcinosis (hard and painful lumps of calcium that form under the surface of the skin).

The skin rash usually appears weeks after the muscle symptoms start appearing. Therefore the child could go months without the condition being diagnosed. The skin and muscle symptoms occur due to blood vessel inflammation, which can be mild to life-threatening, and involve symptoms like joint stiffness, ulcers, contractures, and calcium deposits.

Skin Rashes - The skin rashes do not appear suddenly. The parents can notice these on the eyelids or cheeks of the child. The eyes appear puffy and can be misdiagnosed as allergies. The rash on the eyelids is red and purplish, referred to as heliotrope rash. Another rash that appears on the cheeks gives the appearance of sunburn.

Red patches of dry skin may appear on knuckles, elbows, and knees that take the form of red or scaly patches of skin called Gottron’s papules, which can be misdiagnosed as eczema. The fingernails and the nail beds may also get pinkish.

Muscle Weakness and Pain - The most commonly affected muscles by juvenile dermatomyositis are around the neck, shoulders, belly, hips, and upper legs. These muscles, with time, get weak and start aching, and the patient may have difficulty making common movements like climbing stairs.

In severe cases, the muscles responsible for swallowing and breathing may also get affected, leading to choking while eating, or the patient may always feel short of breath, leading to a hoarse voice.

Joint Pain and Stiffness - The child may complain of red, stiff, sore, and painful joints. However, this can be managed with medication and prevented from causing severe joint damage.

Contractures - It is a condition in which shortening and hardening of the joints, muscles, tendons, or other issues, can occur, leading to deformity, and can be seen in the initial stage of JDM.

Ulcers - Skin or gastrointestinal ulcers may develop in JDM. These are caused by the tissue breakdown surrounding the blood vessels when there is insufficient circulation to the tissue.

Calcium Deposits - In some children, calcium deposits called calcium nodules can occur below their skin and in the muscles. These deposits can vary in size and feel like small, firm pebbles under the skin. Sometimes, these nodules may break through the skin, start draining and cause muscle movement problems.

Digestive Issues - The digestive tract muscles become inflamed, and the food might not be able to move through the digestive tract. The digestive issues faced by the children include the following:

• Swallowing difficulties.

• Pain while swallowing.

• Coughing or choking while eating.

• Stomach pain or discomfort.

• Heartburn.

• Indigestion.

• Chronic diarrhea or constipation.

• Slow stomach emptying (gastroparesis).

• Silent aspiration (where the voice sounds gurgled or wet after swallowing).

• Change in voice, such as hoarseness, pitch changes, or gurgled voice.

• Nasal regurgitation.

2. Juvenile Polymyositis -

This is characterized by chronic muscle inflammation, tenderness, and weakness in the muscles attached to the bones by tendons that help in the movement of the body. This is a very rare form of juvenile myositis and affects both sides of the body, and can make common movements difficult. The severe symptoms of JPM are:

• Fever.

• Shortness of breath.

• Voice changes.

• Problems swallowing.

• Weight loss.

• Calcium deposits in the muscles.

• Joint pain and stiffness.

• Chronic fatigue.

• Heart arrhythmias (abnormal heart rhythms).

3. Benign Acute Childhood Myositis -

This is also known as viral myositis, a sudden onset condition that causes lower extremity pain. The symptoms involve:

• Muscle pain.

• Low extremity pain.

• Refusal to walk due to pain.

• Tiptoe gait (walking on the toes).

What Is the Diagnosis of Juvenile Myositis?

The diagnosis of juvenile myositis can be made by conducting a physical examination and taking a complete medical history of the patient. In medical history, the doctor will ask about the general health of the child, including the family history. During the physical examination, the doctor will examine the skin of the child and test their muscle strength. Along with that, some additional tests may also be performed to confirm the diagnosis, including the following:

• Blood Tests - The blood tests will help identify the certain muscle enzymes present due to inflamed muscle tissues and the antibodies leading to muscle inflammation and weakness.

• Imaging Tests - Magnetic resonance imaging (MRI) can help detect inflammation levels and locate the area of inflammation. Electromyogram (EMG) may also be used to look for nerve or muscle damage.

• Muscle and Skin Biopsy - Biopsy is an absolute method to detect myositis disease. When the affected skin or muscle tissue is examined under a microscope, the inflammatory cells can be seen surrounding and damaging the blood vessels within the muscles or skin.

What Is the Treatment of Juvenile Myositis?

Currently, there is no cure for juvenile myositis, but the symptoms related to it can be managed by taking medications. The goal of the treatment involves:

• To reduce muscle inflammation and damage.

• Maintain and improve muscle strength.

• Manage pain and other symptoms.

Medications:

• Corticosteroids - These are the first line of treatment for myositis and work by restricting the autoimmune response of the body. This helps in restoring muscle strength and reducing pain and inflammation. Steroids can be given orally, via injection, or intravenously. The dosage and duration depend upon the severity of the symptoms.

• Immunosuppressants - These drugs can be given alone or in combination with other drugs that help suppress the immune system of the body, including Methotrexate, Azathioprine, and Cyclosporine.

• Intravenous Immune Globulin (IVIG) - This helps slow down the autoimmune response and can block the harmful antibodies responsible for inflammation that attacks the muscle and skin.

Physical Therapy - This is essential in children with juvenile myositis as it helps maintain and increase muscle strength.

Conclusion:

Juvenile myositis is a rare condition that can be managed by proper medication. The severity of the disease may vary among children. There is no method to check how the child will respond to the treatment and how effective it will be in controlling the symptoms. The most important thing is to take all the medications and physical therapy. Without complications, such children can lead an active and happy life.