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There are several subtypes of juvenile arthritis, one of which is called polyarticular juvenile idiopathic arthritis. This article outlines the causes, symptoms, diagnosis and treatment of polyarticular juvenile idiopathic arthritis.

Juvenile idiopathic arthritis refers to a condition in which children or adolescents develop inflammation and swelling of joints. There are six different forms or subtypes of juvenile idiopathic arthritis, one of which is known as polyarticular juvenile idiopathic arthritis. Approximately 30% of children that develop juvenile idiopathic arthritis have this subtype.

Fortunately, juvenile idiopathic arthritis is not a long-term condition and will eventually improve. In fact, one of the big differences between adult and juvenile arthritis is that if you get the disease as an adult, you will likely have the disease all your life but if you get it as a child, you will outgrow it by the time you are an adult. Hence, most children with the disease recover completely and don’t display symptoms in adulthood.

Patients with polyarticular juvenile idiopathic arthritis demonstrate involvement of five or more joints within the first six months after they have been diagnosed. While it can occur in any joint throughout the body, this subtype usually develops in the small joints of the body, but can also occur in the larger joints. The typical pattern of the disease is that it affects multiple joints at the same time. However, some people will only experience inflammation in one or two joints at the beginning and then progress to involve more joints later on. Polyarticular juvenile idiopathic arthritis can develop at any age during childhood or adolescence, and it has been shown to be more frequently diagnosed in girls compared to boys. Patients with polyarticular juvenile idiopathic arthritis can be either positive or negative for rheumatoid factor, an antibody frequently found in arthritic patients.

Cause of polyarticular juvenile idiopathic arthritis

The cause of polyarticular juvenile idiopathic arthritis is currently unknown. However, it is known that this subtype of arthritis is an autoimmune disease, which refers to a group of diseases that develop due to an impairment in the immune system. While in healthy individuals, the immune system functions to fight against infection and foreign pathogens, in the case of autoimmune disease, the immune system attacks the body’s own healthy tissue instead.

However, while it is known that arthritis is an autoimmune disease, it is not known exactly why it develops. Scientists theorize that the reason why autoimmune arthritis develops is that people that are predisposed to autoimmune disease get exposed to certain environmental triggers, such as smoking or a specific type of food. Unfortunately, triggers for this subtype of disease are not currently known.

Symptoms of polyarticular juvenile idiopathic arthritis

Symptoms tend to come on during periods of time when they intensify, known as flare-ups. Symptoms then subside during a time period known as remission. These are the symptoms associated with the development of polyarticular juvenile idiopathic arthritis:

  • Inflammation, redness, swelling, pain and warmth in joints
  • Stiffness of joints
  • Reduced ability to open the mouth to chew food if the joint of the jaw is involved. This can also lead to abnormal growth of the jaw.
  • Joints in both sides of the body are involved
  • Low-grade chronic fever
  • Rheumatoid nodules, which refers to bumps under the skin
  • Anemia (low red blood cells)
  • Fatigue or weakness
  • Loss of appetite and weight
  • Fell ill or unwell
  • Inflammation of the heart, lungs, eyes and nervous system
  • Limping
  • Trouble with movement of hands, such as handwriting

Diagnosis of polyarticular juvenile idiopathic arthritis

If your child presents with any of the symptoms outlined above, then your family doctor or your child’s pediatrician will likely refer your child to a specialist known as a rheumatologist. Unfortunately, juvenile idiopathic arthritis can be a difficult condition to diagnose and can be confused for other diseases with similar symptoms.

The doctor will make a diagnosis based on several pieces of evidence including asking about symptoms, the family and child’s medical history, physical examination and tests. In the physical examination, the doctor will look for signs of joint swelling, other signs of inflammation and eye complications. The doctor will also likely order different types of tests including:

  • Blood tests to look for markers of inflammation in the blood and to evaluate the presence of anemia
  • Genetic tests, as some genes predispose patients to developing arthritis
  • Imaging tests to determine the severity of joint damage and exclude other diseases.

Treatment of polyarticular juvenile idiopathic arthritis

Children with polyarticular juvenile idiopathic arthritis can suffer from severe joint damage, and thus, strong medication is recommended as soon as the disease is diagnosed. Unfortunately, there is no cure for this disease. However, treatments can be administered to help reduce inflammation, ease pain, make joints stronger, prevent permanent joint damage and complication, stop progression of the disease and improve range of movement. Hence, doctors will often prescribe medication and advise you to use medication alongside performing exercise.

These are the following medicines that the doctor will prescribe:

  • Non-steroidal anti-inflammatory drugs (NSAIDS). These drugs help reduce inflammation and ease pain. NSAIDs are available over-the-counter and include well-known drugs such as ibuprofen and naproxen. It is important to note that NSAIDs can also have severe side effects so it is best to monitor your children when they are taking NSAIDs.
  • Disease-modifying antirheumatic drugs (DMARDs). These help reduce stiffness, pain and swelling of joints. DMARDs take a longer time, between 3 and 6 months, to work and therefore, will likely be prescribed alongside NSAIDs.
  • Xatmep, a type of DMARD. This is a newly approved drug for treatment of polyarticular juvenile idiopathic arthritis that is an oral solution of methotrextate. Xatmep is an aggressive drug that helps decrease joint damage and maintain joint function. Xatmep may be prescribed if your child in non-responsive to NSAIDs.
  • Biologic therapy. These types of drugs are designed to suppress the immune system. Therefore, while they can be effective for arthritis, it also increases your chances of getting an infection. Hence, most biologic therapy is not approved for use in children. 

  • Rosenberg, Alan M., and G. O. Kiem. "Polyarticular juvenile idiopathic arthritis." Textbook of pediatric rheumatology. Elsevier, Philadelphia, 2016. 217-228.
  • Schanberg, Laura E., et al. "Daily pain and symptoms in children with polyarticular arthritis." Arthritis & Rheumatism 48.5 (2003): 1390-1397.
  • Schanberg, Laura E., et al. "Pain, stiffness, and fatigue in juvenile polyarticular arthritis: contemporaneous stressful events and mood as predictors." Arthritis & Rheumatism 52.4 (2005): 1196-1204.
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