Definition

Juvenile Dermatomyositis
What is juvenile dermatomyositis?
Juvenile dermatomyositis is one of the conditions in a group of conditions called the dermatomyositis/polymyositis complex. The conditions in this complex are characterized by muscle damage due to an inflammatory process of the blood vessels that lie under the skin and muscles. Skin changes around the eyelids and over the knuckles and finger joints are also seen. Juvenile dermatomyositis is the condition most often seen in children.
Juvenile dermatomyositis is rare, affecting 3,000 to 5,000 US children under the age of 18.

What causes juvenile dermatomyositis?
The cause of juvenile dermatomyositis has not yet been determined. However, factors which are thought to be associated with dermatomyositis include dysfunction of the immune system, resulting in infections.

What are the symptoms of juvenile dermatomyositis?
The symptoms of juvenile dermatomyositis often appear gradually. At times, there may be a more acute, or intense, onset of symptoms. The following are the most common symptoms of juvenile dermatomyositis. However, each child may experience symptoms differently.

Symptoms may include:
fever
rash around the eyelids and/or knuckles and finger joints;
a rash may also occur on the elbows, knees, and ankles
muscle weakness
fatigue
malaise
muscle pain and tenderness
irritability
weight loss (due to difficulty swallowing)
joint pain and inflammation
calcium deposits under the skin (calcinosis)
mouth ulcers

Symptoms of juvenile dermatomyositis may resemble other medical conditions or problems. Always consult your child's physician for a diagnosis.

Phases of juvenile dermatomyositis:
The course of juvenile dermatomyositis is often divided into four phases, based on symptoms and findings on examination. The four phases are briefly described below:
Prodromal periodThis phase can last for weeks or months. The symptoms seen during this period are nonspecific (general symptoms which can indicate many different conditions).
Progressive muscle weakness and rashIn this phase, muscle weakness increases for days and weeks and then stabilizes. Once the stabilization occurs, it may last from one to two years before recovery.

Persistent muscle weakness, muscle inflammation, and rashDuring this phase, symptoms include persistent muscle weakness, active inflammation of the muscles, and rash lasting up to two years.

Recovery
Recovery may occur without any apparent consequences, or may occur after two or more years with residual muscle weakness, atrophy (wasting), or contractures (a condition in which muscles in a particular location may become permanently paralyzed as a result of lack of use).

How is juvenile dermatomyositis diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for juvenile dermatomyositis may include:
laboratory tests - to assess the presence of antibodies, muscle enzymes, and indicators of inflammation in the blood.
electromyography (EMG) - an electrical test to determine nerve or muscle damage.
muscle biopsy - removal of a small piece of muscle for microscopic examination.
x-rays - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

Treatment for juvenile dermatomyositis:
Juvenile dermatomyositis cannot be cured. However, with supportive therapy and a multidisciplinary team approach to treatment, remission of the disease may be achievable in time. Treatment may include:
medications such as glucocorticosteroids and methotrexate (to treat the inflammatory process) and hydroxychloroquine (to help treat the skin disease of dermatomyositis)
physical and occupational therapy (to improve muscle function and strength)
liberal use of sunscreens (to prevent further irritation or damage to the skin)
nutritional support (to ensure an adequate diet).