What Is Polyarticular Juvenile Idiopathic Arthritis?

Polyarticular juvenile idiopathic arthritis (PJIA) is an autoimmune disease that affects children and teens before the age of 16 and is a type of juvenile idiopathic arthritis (JIA). This chronic disease can cause pain and inflammation in the joints. It involves more than four joints within the first six months of the disease. JIA affects about 294,000 children in the United States, and about 25% of these cases are PJIA.

There are seven types of JIA. They are called idiopathic because no one is really sure what the specific cause of these conditions is. Genes, bacteria, and viruses have all been associated with the development of JIA.

What Is Juvenile Idiopathic Arthritis?

JIA is a group of conditions characterized by joint pain and inflammation that begin before age 16. It is the most common chronic rheumatic disease affecting children. Some of these conditions, like PJIA, are autoimmune disorders, where the immune system malfunctions and the body attacks healthy tissues.

These diseases can affect many joints at once and sometimes even the eyes. It can cause other symptoms such as fevers and a rash.

While the exact cause of these conditions is largely unknown, infections, together with stress and trauma, have been considered a possible etiological factor. Genetics and gut microbiota have also been linked to JIA.

Types

There are seven types of JIA:

• Systemic JIA: This form of JIA affects the entire body. Children with systemic JIA can have high daily fevers that peak in the evening and disappear during the day for at least two weeks, which are a hallmark feature of the disease. They will look and feel sick while the fever lasts, and a rash or enlargement of the lymph nodes, liver, or spleen may appear.
• Oligoarthritis: Four or fewer joints are affected in the first six months of this disease. Pain, stiffness, and swelling mostly affect the ankles or the knees. This type of JIA might be classified as persistent if four or fewer joints are affected after six months or extended if more than four joints are affected after six months. Children with oligoarthritis are more likely to have uveitis.
• Rheumatoid factor-negative polyarticular JIA: This form of JIA affects five or more joints within the first six months of disease. Small joints in the hands and the weight-bearing joints of the lower extremities are the primary targets. Children with this type of JIA test negative for rheumatoid factor (a protein produced by the immune system) in the blood.
• Rheumatoid factor-positive polyarticular JIA: It also affects five or more joints within the first six months of disease. This kind of JIA closely resembles rheumatoid arthritis in adults. Children with this kind of arthritis test positive for rheumatoid factor, and typically have worse joint damage than children with other forms of the disease.
• Psoriatic JIA: Children will also have a psoriasis rash in addition to arthritis. This is a scaly, red rash with white flakes in areas over the joints, the scalp, and behind the ears. Fingernails and toenails may look abnormal too, and eye problems may occur.
• Enthesitis-related JIA: The hips, knees, and feet are most commonly affected in this condition. It causes joint inflammation and inflammation of the areas where tendons and bones meet (entheses). Inflammation in parts of the body other than joints may also occur.
• Undifferentiated arthritis: This is the term given to any form of JIA that doesn't fit the criteria of any of the other forms of JIA.

Different types of JIA are more prevalent in different geographic locations and ethnic groups.

Types of Polyarticular Juvenile Idiopathic Arthritis

PJIA is a form of JIA that affects four joints in the first six months of the disease. It's more common in girls than in boys. It can begin anytime before the age of 16, but rarely happens before the first year of life.

Polyarticular JIA has been thought to represent approximately 15 to 25% of JIA as indicated in North American and European studies. It is more commonly the form of chronic childhood arthritis in Africa, Czech Republic, Kuwait, and India.

There are two forms of PJIA, and they are classified based on the presence or absence of rheumatoid factor.

Rheumatoid Factor-Positive PJIA

In this rarer type of PJIA, blood tests are positive for RF. These proteins mistakenly attack healthy joints, glands, or other normal types of cells. Younger children with the condition rarely have RF. It typically appears in older children between 10 and 13 years old.

Older girls most often have this form of the disease, and it is usually more severe than other types of JIA.

Rheumatoid Factor-Negative PJIA 

In these children, there is no RF in the blood. This is the more common form of PJIA. The condition will still affect more than five joints. There are two peak periods of onset for this type of PJIA:

• Between 1 and 3 years old
• Between 9 and 14 years old

Symptoms of Polyarticular Juvenile Idiopathic Arthritis

The condition progresses quickly over the first six months after symptoms first appear. While this type of JIA can affect many joints, it doesn't affect the entire body.

Symptoms of PJIA across the two subtypes can include:

• Pain and inflammation
• Involvement of symmetric joints (both knees, for example)
• Stiffness
• Warmth over the joints
• Limping
• Mild fever
• Weight loss
• Anemia
• Hepatosplenomegaly
• Mild growth slowing
• Lymphadenopathy

In some cases of RF-positive PJIA, children could have a higher risk of uveitis, and their arthritis could affect them asymmetrically.

Joint pain and inflammation in PJIA typically appear differently based on the age when the condition starts. In younger children, pain begins in joints like knees, wrists, and ankles. In older children and teens, joint pain begins in smaller joints, like the small joints of hands, feet, fingers, wrists, elbows, hips, knees, ankles.

Causes

It is not clear what causes PJIA. Since most autoimmune diseases are triggered by either a genetic abnormality or an immune response to a virus or bacteria, scientists hypothesize that these factors may be linked to the development of PJIA as well. In many cases, families may notice the symptoms of JIA beginning after a child was sick with a cold or some type of infection. The infection and the immune response that followed may trigger an abnormal reaction that causes the body to attack its own tissues.

The genetic basis is not completely understood, but scientists have found that the HLA-A2 is linked to early-onset RF-negative disease, while HLA-DR4 is frequently associated with RF-positive disease. Protective associations have also been identified for both RF-negative and RF-positive PJIA, including DRB1 and DQA1.

Research has also hypothesized that certain environmental factors may contribute to the development of JIA in genetically susceptible individuals, such as breastfeeding and exposure to environmental tobacco smoke.

Diagnosis

PJIA is diagnosed by a thorough physical exam and review of symptoms. There are no specific laboratory tests that will point directly to PJIA as a diagnosis, even though an RF blood test can distinguish between the two types of PJIA. A doctor will run several tests to rule out other conditions.

Abnormal readings of these blood tests could raise suspicions for PJIA or other forms of JIA:

• Complete blood count
• Erythrocyte sedimentation rate
• C-reactive protein
• Complement test
• Hemoglobin
• Hematocrit
• Immunoglobulin
• Antinuclear antibody and other antibody tests
• RF
• Test to check for the HLA-B27 gene

These tests can help identify genetic abnormalities, antibodies, inflammation, and immune dysfunction your child may have. Imaging like X-ray or CT scans might identify signs of joint damage.

Treatment

The treatment of PJIA is focused on reducing pain and inflammation and slowing joint damage. PJIA is a chronic disease and cannot be cured. The majority of children who are treated achieve remission—at least six months with no disease activity—within two to five years.

Medications

Your child's doctor will focus on prescribing medications to calm the inflammation and prevent disease progression.

Medications used to treat PJIA include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) 
• Disease-modifying antirheumatic drugs (DMARD) like methotrexate
• Oral glucocorticoids
• Biologics like TNF or kinase inhibitors that suppress the immune system
• Intravenous immunoglobulin
• Other immunosuppressive medications like cyclosporine and azathioprine

All of the medications used to treat PJIA carry serious side effects. They can create systemic problems, including liver damage. For this reason, treatment progresses through levels of medications as needed to find relief, and some medications may only be used for limited periods of time.

Typically, children will be given glucocorticoid injections first, followed by disease-modifying anti-rheumatic drugs and then biologic agents. Early, aggressive treatment strategies usually lead to the best outcomes and help children affected by this disorder reach remission quicker.

Since many of the medications used to treat PJIA have such high potential toxicity and carry the risk of systemic organ damage, many physicians prefer to prescribe biologic agents, which work to decrease the activity of immune cells and lower inflammation.

Physical Therapy

Physical therapy is an important part of the treatment process for PJIA. As the disease progresses, physical therapy can be used to help relieve pain. Alongside medications, it can also be used to restore mobility and function. Physical and occupational therapy can both be beneficial, especially for children with weakness or contractures.

• Physical therapy primarily includes stretching and range of motion exercises.
• Occupational therapy puts an emphasis on helping children learn to perform the activities they need to do every day, like bathing and writing in school.

Exercise 

Regular exercise can help with:

• Flexibility
• Pain control
• Weight management
• Bone health
• Building muscles to support joints
• Improving mood and energy
• Better sleep
• Increasing confidence

Even with these benefits, though, you must be sure that exercise is safe for your child. You may want to consult with your child's doctor or physical therapist before beginning an exercise program. Children with problems balancing or extreme weakness and joint damage may need to modify some exercises for safety.

Some of the best exercises for children with JIA include:

• Water exercise
• Bicycling
• Yoga
• Tai chi

Foods to Fight PJIA

Nutrition is also a big part of managing PJIA. Nutrients like folic acid, calcium, and vitamin D can help support bone and joint health. There is also evidence that anti-inflammatory diets—eating or avoiding certain foods that contribute to inflammation—can help control diseases like JIA.

Some foods to include in your child's diet are:

• Clean proteins
• Fiber-rich foods
• Plant-based diets
• Herbs and spices with anti-inflammatory properties like turmeric and cinnamon
• Foods rich in omega-3
• Calcium-containing foods or supplements
• Foods rich in vitamin D
• Folic acid supplements when taking medications like methotrexate

Your child should avoid foods like:

• Food and drinks high in sugar
• White starches
• Saturated and trans fats
• Artificial foods
• Charred foods, like foods that are blackened on the grill

Complications

A number of complications can arise from juvenile arthritis if it is not well-managed. Effectively treating inflammation and slowing disease progression can help reduce your child's chances of developing long-term joint and bone damage.

Complications that can arise from uncontrolled PJIA include:

• Bony erosions: The wrist and hip joints are particularly at risk for bony erosions.
• Joint destruction: In severe cases, joints can become so damaged that they can no longer be used.
• Osteopenia and osteoporosis: Medications used to treat PJIA, like glucocorticoids, can reduce bone density or the concentration of the nutrients that make bones strong.
• Chewing problems: In some cases, your child may have involvement of the temporomandibular joint (TMJ). This can reduce the mobility of your child's jaw, making chewing or talking more difficult.
• Movement problems: As PJIA progresses and joint movement becomes limited, children can develop complications simply from the lack of mobility, including contractures, overall weakness, and trouble walking.
• Vision problems: Uveitis, an inflammation of the eye, is sometimes seen in children with PJIA and systemic JIA. It usually has no symptoms, but can impair vision. Children with PJIA should have their vision checked regularly. Those with RF-negative PJIA are more at risk of developing this condition than those who are RF-positive.
• Organ damage: Organ damage rarely occurs with PJIA as it does with systemic JIA or rheumatoid arthritis. However, damage may come as a result of medications used to treat PJIA.
• Macrophage activation syndrome: This complication causes fatigue, fevers, and enlarged liver, spleen, and lymph nodes due to excess proliferation of immune cells. It is a major complication of JIA that can sometimes be fatal.

Coping

Children with PJIA are very likely to experience stress or depression due to their condition. A strong support system that includes family, therapists, counselors, and peer groups can help.

Other ways to help your child cope with PJIA include:

• Encourage your child to get enough sleep
• Encourage exercise and physical therapy, and find ways to make it fun
• Work with your child's school to make sure your child has help as needed
• Work with other caregivers to help your child take part as much possible in school, social, and physical activities
• Get special help for your child under Section 504 of the Rehabilitation Act of 1973 if they qualify
• Help your child find a support group to connect with other children who also have JIA

The Arthritis Foundation has a program that pairs children with PJIA with young adults who share their experience called iPeer2Peer. It offers a number of resources for children of all age groups with PJIA.

A Word From Verywell

Dealing with a chronic disease can be difficult for children and caregivers alike. PJIA, because of the number of joints involved, can lead to mobility problems and change the way a child can interact with their peers. While PJIA cannot be cured, there are a number of treatments that can help children with this disease and allow them to continue living a normal life. It may seem like a daunting challenge for you and your child, but know that with early treatment, a good medication regimen, physical therapy, and a strong support system, your child can have fewer symptoms and experience less impact of the disease.