Getting the Diagnosis

Most families begin at their primary care physician, who will take a medical history and observe your child’s symptoms. Children present with many different symptoms, but often, the first symptom is a skin rash. This can go misdiagnosed, so take notes and make careful observations about the rash. When did it first occur, does it change based on exposure to different things (sun, food, activities, weather), where is it located, did it present after an infection or illness, etc. The next symptom that may accompany the rash (or may present later) is muscle weakness. Along with these notes, photo documentation can be integral in the diagnosis process. Taking photos along the way of the rash to show or send to doctors can be a key in helping receive a proper diagnosis. A physical examination will allow a doctor to observe the difficulty a child has with certain movements. They may ask a child to get themselves off the floor or out of a chair, demonstrate walking up steps, or squeezing something in their hands. The medical history and physical examination may help your doctor come to a diagnosis, but often more information is needed.

The next steps might include: blood tests, diagnostic tests, and muscle and/or skin biopsies. These next steps might also include referrals to rheumatologists (who specialize in chronic inflammatory conditions that involve muscles) or dermatologists (who specialize in looking at the skin). Cure JM has a list of doctors in our clinical care network that are specialists at diagnosing and treating JM https://www.curejm.org/clinical-care-network/ or reach out to us at info@curejm.org for a doctor in your area.

Blood tests or labs are tests in which a sample of blood is taken from an individual, usually via a needle. There are several different things doctors will be looking at in a blood test. They will likely look for autoantibodies and the levels of different muscle enzymes. Various types of JM exist, and those different types can be identified by the different autoantibodies found in the blood. These are often referred to as Myositis Specific Autoantibodies or MSAs. An autoantibody is a protein in the blood that, instead of helping a person’s body repair or get better, it mistakenly attacks the body. A muscle enzyme level shows the doctor how much inflammation or damage exists in certain muscles. Some muscle enzymes you may see tests for include: Aldolase, Creatine Kinase (CK), and Lactate Dehydrogenase (LDH).

When looking at labs, keep in mind that over time, labs can normalize, and a child with juvenile myositis may present with normal labs and/ or no autoantibodies may be found.  This is one reason why it can be helpful to be evaluated by a pediatric rheumatologist who specializes in diagnosing and treating juvenile myositis.  

Following blood tests, a diagnostic test may be given. In the case of JM, this may come in the form of Magnetic Resonance Imaging (MRI), Electromyogram (EMG), and/or Nerve conduction velocity (NCV). In most cases, children are given an MRI. Depending on the age of the child, they may be put under sedation for this 30–90-minute procedure in which digital images are taken of the muscles using a powerful magnetic field and radio waves. This process will allow doctors to see the inflammation in muscles.

Lastly, a muscle or skin biopsy may be performed. In most cases, a muscle biopsy is preferred over a skin biopsy as it is one of the best ways to diagnose myositis. For this test, a portion of the muscle is removed with a needle or scalpel. Following the removal of the muscle tissue, doctors can look at it under a microscope to determine the disease activity of the cells present.

For more information on symptoms and about juvenile myositis visit our “What Is Juvenile Myositis” page by clicking here.