Juvenile Myositis

Juvenile Myositis

Overview

Juvenile Myositis (JM) is found in children under the age of 18 and affects two to four children per million. The most frequent form of juvenile myositis is juvenile dermatomyositis (JDM), in which children experience marked muscle weakness and skin rash. Juvenile polymyositis can also occur in children, but it is extremely rare. There is no known cause or cure for juvenile myositis. However, there are treatments that can successfully manage the symptoms.

Symptoms

The following are common signs and symptoms for juvenile dermatomyositis and polymyositis:

Reddish-purple rash over the eyelids or joints

General tiredness

Moodiness or irritability

Complaints of tummy aches

Trouble climbing stairs or onto a bus, standing from a seated position, or getting dressed

Difficulty reaching up, like to shampoo or comb hair

Trouble lifting the head

Swelling or redness in the skin around the fingernails

Gradual muscle weakness, most often those closest to the body such as neck, stomach, upper arms, and legs

Hardened lumps or sheets of calcium (calcinosis) under the skin

Trouble swallowing (dysphagia)

Hoarse-sounding voice

Skin Rash

As is the case for dermatomyositis, the first sign of JDM is usually a skin rash. The rash may be red and patchy, like dry skin; a red or purplish color on the eyelids or cheeks that may look more like allergies; or both. Gottron’s papules, rashes, or lesions over the knuckles, elbows, and knees, and heliotrope rash, a purplish rash around the eyes, are common.

Children with juvenile polymyositis do not experience skin symptoms.

Muscle Weakness

JDM patients can have weak muscles at the same time they see the skin rash, or the weakening muscles may occur after the rash over days, weeks, or months. The weaker muscles are usually those closer to the body, in the neck, shoulders, back, and torso. The child may have trouble climbing or standing from a seated position.

The skin rash and weak muscles are caused by inflammation or swelling in the blood vessels under the skin and in the muscles.

Other Symptoms

Other signs may include falling, weaker voice (dysphonia), or problems swallowing (dysphagia). About half of the children with JDM have pain in their muscles. Some children may also develop calcinosis, in which hardened lumps or sheets of calcium develop under the skin. Contractures can also occur, where the muscle becomes shortened and causes the joint to stay bent. Exercising the muscles and joint range of motion can prevent contractures.

If your child is experiencing any of these juvenile myositis symptoms, we encourage you to talk to your doctor to begin the diagnosis process. Since juvenile myositis is a rare disease, not all physicians are familiar with the signs and symptoms. If you are struggling to find an accurate diagnosis, visiting a specialist can help.

Causes

Researchers believe a convergence of environmental and genetic factors causes juvenile myositis. Children who develop this disease may have a family history of other autoimmune diseases, including thyroid disorder, type I diabetes, rheumatoid arthritis, lupus, or Crohn’s disease.

Juvenile myositis is a heterogeneous disease, presenting differently in each child and can be triggered by an array of genetic or external environmental factors.

If a child is genetically predisposed to JM, experts suspect that a virus or bacteria might trigger a runaway immune response that causes the body to attack itself. Other environmental factors, such as a heavy dose of sun exposure, may also play a role.

Diagnosis

A doctor will perform a complete physical exam, specifically looking for rashes and muscle weakness. If JM is suspected, blood tests are the next step in making a diagnosis. Muscle enzymes, including creatine kinase (CK), aldolase, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), are measured.

If these lab tests are elevated, enzymes leak from inflamed or damaged muscles into the bloodstream. Antinuclear antibodies (ANA) are also measured to see if the child’s body produces antibodies against its own cells. Several myositis-specific autoantibodies have also been identified, which can be tested. Other blood tests are sometimes available to check immune activation and/or blood vessel damage. The next step in diagnosing JM is usually an MRI that detects muscle inflammation and damage.

A muscle biopsy may be performed to finalize the diagnosis if the MRI shows evidence of diseased muscles. When the characteristic rashes are absent, a muscle biopsy must be performed to exclude other causes of muscle weakness. A small amount of muscle is removed for examination under a microscope to determine if and how much the disease affects the muscles and blood vessels.

Treatment

Although medications can help alleviate the symptoms of JM, the disease has no known cure. The primary medications used to treat the symptoms of JM are corticosteroids, immunosuppressants, and chemotherapy. These medications can cause severe side effects, making JM challenging to treat. Many researchers believe that early and aggressive treatment is usually the best predictor of a better outcome for this disease.

High-dose oral Prednisone or other corticosteroids, often coupled with intravenous corticosteroids and Methotrexate, are usually the first line of treatment for JM. Since the side effects of corticosteroids can be severe, Methotrexate, a chemotherapy drug administered at much lower doses than used for cancer patients, is usually introduced early to allow for tapering of the corticosteroids.

Second-line treatments are often considered as alternative treatments to allow patients to wean off of the steroids and methotrexate, or as an additional therapy if the first-line treatments are not sufficiently controlling the disease.

Common second line treatments include Intravenous Immunoglobulin (IVIG), Hydroxychloroquine (Plaquenil), Rituximab (Rituxan), Mycophenolic Acid or MMF (brand name CellCept or Myforic).  Others may include Cyclosporine, Tacrolimus (Prograf), or Azathioprine (Imuran).  

Some additional options that you may want to discuss with your doctor include Abatacept (Orencia), Tofacitinib (Xeljanz), TNF inhibitors, Tocilizumab (Actemra), Anakinra (Kineret), and Sifalimumab.  

In addition, if you are dealing with calcinosis (a complication of JM), you might discuss with your doctor possible treatments for calcinosis including sodium thiosulfate (an IV treatment for calcinosis being studied at the NIH) and bisphosphonates (which has had some effects at reducing calcium deposits).  

We know that JM is different for each patient, so always discuss your options with your doctor.  

In addition, you may discuss with your doctor the importance of exercise, nutrition, quality sleep, protection from UV sunlight (sunblock and sunscreens), and vitamin D and calcium supplements.

Type of Doctor Department : A pediatric rheumatologist