Juvenile Myositis (JM) is found in children under the age of 18 and affects 3,000 to 5,000 children in the United States. The most frequent form of JM is juvenile dermatomyositis (JDM), in which children experience marked muscle weakness and skin rash. The other form of myositis that can occur in children—juvenile polymyositis—is extremely rare.
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. Children with juvenile polymyositis do not experience skin symptoms.
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 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 develop calcinosis, hardened lumps or sheets of calcium under the skin. Contractures can also occur in which the muscle becomes shortened, causing the joint to stay bent. Exercising the muscles and joint range of motion can prevent contractures.
Signs and symptoms:
- 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
- Characteristic rashes of JDM—Gottron’s papules (rashes or lesions over the knuckles, elbows, and knees) and heliotrope rash (purplish rash around the eyes)
- 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