Definition of Myocarditis - pediatric:

Pediatric myocarditis is inflammation and weakness of the heart muscle in an infant or young child.

Causes, incidence, and risk factors:

Myocarditis is an uncommon disorder. In children it is usually caused by viral infections that reach the heart, such as the influenza (flu) virus, Coxsackie virus, and adenovirus. However, it may also occur during or after other viral or bacterial infections such as polio, rubella, Lyme disease, and others.

When you have an infection, your body's immune system produces special cells that release certain chemicals to fight off disease. If the infection affects your heart, the disease-fighting cells enter the heart. However, the chemicals they produce can damage the heart muscle, causing it to become thick and swollen. This leads to symptoms of heart failure. In addition, the virus or bacteria damage the heart muscle.

Other causes of pediatric myocarditis may include:

• Allergic reactions to certain medications
• Being around certain chemicals
• Certain diseases (autoimmune disorders) that cause inflammation throughout the body
• Certain drugs
• Infections due to fungus or parasites
• Radiation

Pediatric myocarditis tends to be more severe in newborns and young infants than in children over age 2.