One of the most common subtypes of juvenile idiopathic arthritis is known as oligoarticular juvenile arthritis, which has an estimated annual incidence of between 1 and 20 children per million. This subtype of juvenile idiopathic arthritis is much more frequently diagnosed in girls compared to boys. In fact, females make up 80% of all cases of oligoarticular juvenile arthritis. Most patients that develop this disease tend to be between 2 and 4 years of age.
Arthritis, in general, simply refers to inflammation of joints, though the types of joints and numbers of joints involved can vary on each subtype. In patients with oligoarticular juvenile arthritis, the joint presentation tends to asymmetrical, which means that it only affects joints on one side of the body, and usually affects four or less joints. These joints tend to be located in the lower limbs, so the knee or foot joints.
Cause of oligoarticular juvenile idiopathic arthritis
The exact cause regarding why oligoarticular juvenile arthritis develops is currently unknown. However, what is known is that oligoarticular juvenile arthritis is an autoimmune disorder. Generally, the immune system has a responsibility to protect us from foreign, potentially disease-causing pathogens such as bacteria, viruses and fungi. However, in the case of the autoimmune diseases, the immune system is impaired and confuses the body’s own healthy tissue for a foreign object and starts to attack it. In the case of oligoarticular juvenile arthritis, the immune system attacks the joints, leading to joint inflammation and swelling.
However, the immune system needs to be triggered to react this way and unfortunately, researchers are unsure as to what the triggering are factors for this disease. Studies have implicated the role of genetics in the development of this disease as patients that have the gene HLA DR3 and DRB1*08 are more likely than others to develop it.
Symptoms of oligoarticular juvenile idiopathic arthritis
Interestingly, most patients with oligoarticular juvenile arthritis don’t present with pain, so the reason why they seek medical help is because the patient is experiencing issues regarding swelling of joint or limping. There are two different subtypes of oligoarticular juvenile arthritis, each with its own unique symptomatic presentation. While most symptoms are common across both subtypes, there are some that are unique to each.
These are the symptoms associated with oligoarticular juvenile arthritis by each subtype:
1. Oligoarticular-persistent juvenile arthritis. This subtype is actually the mildest and most common type of juvenile arthritis. Patients in this subtype experience flares and remission, which are periods of time when the disease worsens and when the symptoms disappear, respectively. Children with this subtype continue to only have involvement of four or less joints after six months post-diagnosis of the disease. Furthermore, while this disease can involve inflammation of multiple joints, they are not all inflamed at the same time. These are some facts to know about oligoarticular-persistent juvenile arthritis:
- The most common joints involved in the manifestation of this disease are joints of the knee, ankle, and elbow.
- Most patients with the disease will not experience problems in health or growth.
- Symptoms of the disease manifest in children than usually younger than four years.
- 20% of children with oligoarticular-persistent juvenile arthritis will develop uveitis (inflammation of the eye).
2. Oligoarticular–extended juvenile arthritis. About 20-30% of patients with oligoarticular arthritis will progress to extended arthritis. Patients in this subtype of arthritis present with involvement of only four or less joints within the first six months of diagnosis. However, patients then progress and have involvement of five or more joints at a later time point. These are some facts to know about oligoarticular-extended juvenile arthritis:
- Both large and small joints are involved in the disease.
- Similar to oligoarticular-persistent juvenile arthritis, patients experience flares and remission periods.
- Uveitis is also frequently diagnosed in patients with oligoarticular-extended juvenile arthritis.
As uveitis is a feature of both oligoarticular juvenile arthritis subtypes and it often isn’t accompanied by visible features such as pain or redness of the eye, it is important to continuously follow-up and have regular check-ups with eye specialists.
Oligoarticular juvenile arthritis is mild, and therefore, it is rare for patients to experience any permanent joint damage if the disease is diagnosed and treated accordingly. While some people will go into permanent remission, others will find that their disease continues into adulthood.
Diagnosis of oligoarticular juvenile idiopathic arthritis
Making a diagnosis of juvenile oligoarticular juvenile idiopathic arthritis can be difficult for physicians as joint pain in children can be the result of several different conditions. To add to the complexity, there is not one single test that can be conducted to help determine the diagnosis. Instead, tests are done to exclude the possibility of other diseases. In order to establish a diagnosis and exclude other diagnoses, the physician will administer these types of tests:
- Blood tests to evaluate erythrocyte sedimentation rate and c-reactive protein levels, which help determine levels of inflammation. Other blood tests can be administered to determine a diagnosis of juvenile idiopathic arthritis as these children often have high levels of anti-nuclear antibody, rheumatoid factor, and cyclic citrullinated peptide.
- Imaging tests such as X-rays and magnetic resonance imaging can help exclude other diseases, and help detect the severity of joint damage.
Treatment of oligoarticular juvenile idiopathic arthritis
Physicians focus on treating oligoarticular juvenile idiopathic arthritis through a combination regimen that involves medication to ease pain and swelling, exercise to help maintain an adequate level of physical activity, and lifestyle modifications. These are the following therapies that the doctor may prescribe:
- Medications. A physician may prescribe a number of different medication such as non-steroidal anti-inflammatory drugs to help decrease pain and inflammation, disease-modifying anti-rheumatic drugs (DMARDs) to ease joint pain and inflammation, biologic agents that help decrease inflammation and joint damage, and finally corticosteroids, which treat inflammation.
- Physical therapy. Working with a physical therapist can teach a patient strategies and exercises to keep joints flexible and stay as active as possible.
- Surgery. In extreme cases, physicians may recommend conducting a surgery to improve position of the joint or replace a joint.