What is Juvenile Idiopathic Arthritis?
Juvenile idiopathic arthritis, or JIA, is a variety of arthritis (joint inflammation) that affects children under 16 and lasts for six weeks or more. Over time, the terms used to describe this sort of long-lasting arthritis in children have changed. It used to be called juvenile chronic arthritis and juvenile rheumatoid arthritis, but since 1995, we’ve been using the term JIA.
In 2001, a major conference on rheumatology (the study of arthritis and other similar diseases) identified seven types of JIA. These are: a) oligoarthritis, or arthritis affecting four or fewer joints; b) rheumatoid factor positive polyarthritis, arthritis in five or more joints and a positive blood test for a substance called rheumatoid factor; c) rheumatoid factor negative polyarthritis, similar but without a positive blood test; d) systemic arthritis, affecting entire body systems rather than just joints; e) psoriatic arthritis, associated with the skin condition psoriasis; f) enthesitis-related arthritis, when the sites where tendons and ligaments attach to the bone are inflamed; g) undifferentiated arthritis, a category for when it’s not clear which type a child has.
Even though all of these types involve long-lasting arthritis, they have distinct characteristics, genetic factors, underlying causes, lab test results, disease progression, and outcomes. Each type also involves different symptoms outside of the joints and may also cause problems in other parts of the body, depending on the specific type.
Recently, a group called the Pediatric Rheumatology International Trial Organization has put forward a new set of classifications for JIA, which they are currently testing for validity.
What Causes Juvenile Idiopathic Arthritis?
The exact cause of chronic arthritis, as seen in Juvenile Idiopathic Arthritis (JIA), is still a mystery. It is speculated that it could be due to abnormal reactions of the body’s defense system, triggered by environmental factors in someone who is genetically prone to the disease. Some life experiences, like exposure to antibiotics or being born through a C-section, could potentially increase the risk. On the other hand, breastfeeding and having siblings around the house may provide some protection.
While some studies hint at a potential role played by certain microorganisms, such as Parvovirus B19, Epstein-Barr virus, certain gut bacteria, Chlamydophila pneumoniae, and streptococcal infections, the evidence isn’t clear-cut.
Interestingly, your genes seem to play a significant role. This is suggested by studies that show similar disease patterns in identical twins, who share the same genes. They found that specific genetic markers, known as Human Leukocyte Antigen (HLA) alleles, and some non-HLA genes might be linked to specific types of JIA and eye inflammation (uveitis).
Certain genetic markers were associated with different forms of JIA. For instance, HLA-A2, HLA-DRB1:11, and HLA-DRB1:08 were linked to oligoarticular JIA and Rheumatoid Factor (RF) negative polyarticular JIA, while HLADRB1:01 and HLADRB1:04 were linked with RF-positive polyarthritis. Some markers were noted in systemic JIA and psoriatic JIA as well. Furthermore, certain markers seemed to predispose people to developing JIA earlier.
Overall, it seems like a combination of environmental factors and genetics could play a role in causing chronic arthritis in Juvenile Idiopathic Arthritis.
Risk Factors and Frequency for Juvenile Idiopathic Arthritis
Juvenile Idiopathic Arthritis (JIA) is the most widespread disease affecting joints in children in the Western world. The occurrence of this illness changes across different studies and locations, ranging from 1.6 to 23 new cases per 100,000 children. In the US and Canada, the frequency of JIA is recorded to be between 0.041 to 0.061 per 1,000 children. With siblings, the chances of getting this condition can escalate from 15 to 30 times, similar to the pattern seen with type 1 diabetes.
- There are different categories of JIA, with each having a unique distribution percentage.
- Oligoarthritis is found in 50% to 60% of cases.
- RF-negative polyarthritis is seen in 11% to 28% of cases.
- RF-positive polyarthritis affects 2% to 7% of patients.
- Systemic arthritis is prevalent in 10% to 20% of cases.
- Psoriatic arthritis impacts 2% to 15% of patients.
- Enthesitis-related arthritis ranges from 1% to 7% of cases.
- The prevalence of these subtypes can vary based on geographical locations. For instance, RF-negative polyarthritis is more common in North America, while oligoarthritis occurs more frequently in southern Europe. Southeast Asia sees higher instances of systemic arthritis and enthesitis-related arthritis, but uveitis is most widespread in northern and southern Europe.
- The majority of JIA subtypes are more common in females. However, enthesitis-related arthritis usually affects males, while systemic JIA happens equally among males and females.
Signs and Symptoms of Juvenile Idiopathic Arthritis
Juvenile idiopathic arthritis (JIA) is a rather unpredictable disease. Some individuals may experience a disease that eventually gets better on its own, while others may have a persistent disease that poses a high risk of joint damage.
JIA generally presents with signs of an inflammatory joint disease such as swelling within the joint (synovitis), fluid build-up in the joint (joint effusion), swelling of soft tissue, bone thinning (osteopenia), bone swelling (bone edema), and joint surface damage (erosions). Age-specific elements like disturbances in growth at the end of long bones (epiphyseal growth disturbances), early fusing of the growth plate (premature physeal fusion), and inequality in limb length can also occur.
To diagnose and appropriately classify JIA, a comprehensive history is necessary. This includes the age when the symptoms began, the joints affected, how long the arthritis has been present, any related symptoms or diseases, and physical and musculoskeletal examinations.
Typically, JIA is considered when a child younger than 16 years has had arthritis for at least six weeks and other causes of long-term arthritis have been ruled out.
Testing for Juvenile Idiopathic Arthritis
While there’s no direct test for diagnosing and determining the extent of Juvenile Idiopathic Arthritis (JIA), there are many valuable steps.
For example, your doctor may begin by conducting a range of laboratory tests such as a Complete Blood Count (CBC), Erythrocyte Sedimentation Rate (ESR), and C-reactive protein (CRP) test. These tests can give doctors insights into your overall health and importantly reveal the presence of inflammation in the body. Antinuclear antibody (ANA), Rheumatoid factor (RF), anti-CCP, and HLA-B27 are specialized tests that might help your doctor better understand your JIA. RF or anti-CCP results are typically limited in their diagnostic usefulness but may suggest a more severe progression of the disease. Further tests may be necessary if there are concerns about complications like macrophage activation syndrome (MAS), which is a severe and potentially life-threatening complication of JIA.
Imaging is another helpful means of narrowing down your diagnosis and evaluating any damage in your joints. X-rays are often the starting point for imagining the affected joints. However, in early stages of JIA, changes may not be visible on x-ray. Indirect signs to look for in x-ray images include increased density in soft tissue, dislocation of fat folds, and soft tissue swelling. Other features like bone erosion, damaged joints and bone deformity might be visible in later stages of the disease.
Ultrasound (US) is a handy tool for doctors in cases of JIA. It’s easily accessible, emits no harmful radiation and allows doctors to compare the affected and non-affected sides. US is helpful in evaluating joint effusion, synovial thickening (or joint lining thickening), inflammation of the joint cavity, tendons and their covering (tenosynovitis), points where the tendons or ligaments attach to the bone (enthesitis), as well as bone erosion. Doctors prefer US for its accurateness and it plays a significant role in treatment planning such as guiding corticosteroid injections into joints.
Sometimes, doctors turn to Magnetic Resonance Imaging (MRI) – the “gold standard” tool to study JIA. Compared to other imaging modes, it provides the most detailed images of the joints and tissues affected by inflammation. It is unique as it can show bone marrow edema, a clear sign of inflammation not visible on other imaging methods.
Finally, to determine the JIA subtype, doctors combine their clinical observations with laboratory test results like RF and HLA-B27. There are different subtypes of JIA like oligoarthritis, rheumatoid factor negative polyarthritis, rheumatoid factor positive polyarthritis, systemic arthritis, psoriatic arthritis, and enthesitis-related arthritis, each with their specific diagnostic criteria based on symptoms, the number of joints affected, and presence of specific test markers. If the JIA doesn’t fit into any subtype or meets the criteria for two or more subtypes, it is classified as “undifferentiated arthritis”.
Treatment Options for Juvenile Idiopathic Arthritis
Juvenile Idiopathic Arthritis (JIA) – a type of arthritis that affects children – requires several methods of treatment. This includes medication that reduces inflammation and supports the immune system, physical therapy, and possibly even surgery. Factors such as the subtype of the disease, its severity and associated damage, any other health conditions, as well as a family’s comfort with the treatment plan, all play a role in determining the best course of treatment.
Drugs known as Nonsteroidal Anti-Inflammatory Drugs (or NSAIDs for short) are generally the first line of treatment and provide symptomatic relief for all variations of the disease. With newer, more aggressive treatments available, including drugs like methotrexate and medicines called biologics, the use of NSAIDs in treating JIA has decreased over time.
Physical therapy, another critical part of JIA management, focuses on maintaining a good range of motion for the joints. Bearing minimum stress on the joints while exercising is important, making activities such as swimming often a good choice. Encouraging kids to stay active through moderate fitness routines, enhancing flexibility, and exercises that help to strengthen the muscles is beneficial.
What else can Juvenile Idiopathic Arthritis be?
The process of correctly diagnosing chronic arthritis can be complex as Juvenile Idiopathic Arthritis (JIA), a common type of arthritis in children, is diagnosed by excluding other diseases. This means your doctor will rule out other conditions before diagnosing JIA. The diseases to be ruled out vary depending on the symptoms and type of JIA.
For example, in the following types of JIA, doctors need to exclude these conditions:
- Oligoarthritis: conditions like reactive arthritis following strep infection, Lyme disease, acute rheumatic fever, toxic synovitis, septic arthritis, sports injuries, the effects of certain drugs, diseases like sickle cell and hemophilia, bone infections and tumors, leukemia, and lymphoma.
- Polyarthritis: similar conditions to oligoarthritis plus diseases like lupus, mixed connective tissue disease, Sjögren syndrome, arthritis related to bowel diseases, and amplified musculoskeletal pain syndrome might need to be excluded as well.
- Systemic arthritis: doctors may also consider excluding infections like mycoplasma, syndromes such as Kawasaki and the PFAPA syndrome (Periodic Fever, Aphthous stomatitis, Pharyngitis and Adenitis syndrome), various types of vasculitis, bowel diseases, and cancers like leukemia, lymphoma, and neuroblastoma.
- Enthesitis-related arthritis: conditions like Osgood-Schlatter disease, inflammatory bowel diseases, CRMO (Chronic Recurrent Multifocal Osteomyelitis), and amplified musculoskeletal pain syndrome may need to be excluded.
Joint pain (arthralgia) is a common early sign of systemic JIA, however, arthritis is not always a prominent feature. Any joint can become involved when arthritis starts to show. The most common affected areas are the wrists, knees, and ankles. The hands, hips, neck (cervical spine), and jaw joints might also get affected.
In the world of general practice, joint pain in children is a usual concern and becomes notably more common after the age of ten. Among these musculoskeletal complaints, joint and soft tissue pain are the most prevalent (encompassing 65% of cases). The most common cause of these complaints in children of all ages is found to be physical injury (accounting for 45% of cases).
What to expect with Juvenile Idiopathic Arthritis
The future outlook of Juvenile Idiopathic Arthritis (JIA), a type of arthritis affecting children, has significantly improved in recent years, mainly due to new drugs that can target and stop the biological processes causing ongoing inflammation. A quick and accurate diagnosis, followed by effective treatment, is crucial to prevent lasting damage to the joints and maintain their function.
Some research suggests there might be a “window of opportunity” early in the disease. If addressed with treatment promptly during this phase, there’s a higher likelihood of the condition going into remission and better long-term results.
A recent study involving 168 patients showed that, without medication, 48.8% of cases went into remission. With medication, 49.9% experienced remission or minimal disease activity. Only a small fraction, 1.3% of patients, did not respond to treatments. Interestingly, patient’s age, specific symptoms, course of the disease, or laboratory results, did not seem to be linked to how long they stayed in remission.
Possible Complications When Diagnosed with Juvenile Idiopathic Arthritis
The main complications of Juvenile Idiopathic Arthritis (JIA) are most often seen as differences in leg length and stiff joints that can’t move the full range of motion. One potentially serious complication is the macrophage activation syndrome, brought on by the unchecked activity and growth of certain immune cells, known as T lymphocytes and macrophages. It’s unclear how often this syndrome happens in JIA patients, though some research suggests it could be in up to 10% of cases.
Other significant complications include slowed growth, reduced bone density for their age, severe hip problems requiring a hip prosthesis, and amyloidosis, an abnormal protein that can deposit in various tissues and organs.
Key Complications:
- Differences in leg length
- Joint stiffness and restricted motion
- Macrophage activation syndrome
- Slowed growth
- Lower than normal bone density for age
- Severe hip problems requiring a hip replacement
- Amyloidosis (abnormal protein deposits)
Preventing Juvenile Idiopathic Arthritis
If a child has a long-term and disabling condition like Juvenile Idiopathic Arthritis (JIA), it’s important to educate both the child and their family about the condition. There have been many efforts and studies focused on how to achieve this. Some of the recent and innovative strategies include the use of comic books to help children understand their condition, as well as the incorporation of artificial intelligence. This means using technology to assist with learning and understanding about JIA.