Different types of juvenile idiopathic arthritis (JIA) exist. The purpose of this section is to discuss the importance of enthesitis in JIA and how it is under recognised.
Doctors working in this area have designated several types of disease. They have not adopted the concept of joint inflammation that is either synovial based (joint lining) or entheseal based (Fig 1).
|McGonagle et al Lancet 1998. In Rheumatoid Arthritis it is considered that inflammation starts in the joint lining which is called the synovium. In Psoriatic Arthritis it is recognised that the inflammaton may start at the enthesis and then spread to the adjacent bone and synovium and other tissues|
This page deals specifically with the importance of unrecognised enthesitis in different types of JIA
This is the commonest type of JIA and affects about two-thirds of children and young people with arthritis. In common with enthesitis associated arthritis in adults this type of JIA tends to affect the large joints of the lower limbs.
This form of arthritis is often mild and eventually resolves in many cases. However, children with Psoriatic Arthritis typically develop the skin psoriasis several years later.
Psoriatic Arthritis is strongly linked to enthesitis so it is clear that some types of oligoarticular JIA are enthesitis linked.
This type of JIA is associated with chronic anterior uveitis (inflammation of the eye). Inflammation in the anterior eye is strongly associated in adults with enthesitis associated arthritis.
This eye inflammation doesn't cause a red or painful eye but can still cause reduced vision if it isn't treated. Adult anterior uveitis is extremely painful which is very distinct.
This difference may be due to the immune system in the anterior part of the eye that may dampen inflammation in children.
This pattern of eye disease could be linked to entheseal abnormalities in the eye. This is still a research question.
This type of JIA leads to multiple painful swelling in fingers, toes, wrists, ankles, hips, knees, and the neck and jaw.
The symptoms may continue into adulthood. Some of these cases develop psoriasis in late childhood and adult pointing towards an entheseal related pathology.
The Oligoarthritis pattern typically spreads to involve 5 or more joints and shows a tendency for the large joints.
Occasionally some cases eventually develop psoriasis which points towards an enthesis associated pathology in this subgroup.
This form of JIA is clearly recognised as an enthesitis related arthritis since insertions of the heels and knees may show pain, swelling and tenderness.
In contrast to the uveitis of oligoarticular JIA, this type of JIA is associated acute uveitis.
It may be associated with the development of stiffness in the neck and lower back in teenagers and young adults. It can thus evolve into Ankylosing Spondylitis.
Patients typically carry the HLA-B27 marker.
As of 2013 paediatricians still don't fully appreciate the importance of clinically unrecognised enthesitis in Psoriatic Arthritis.
This type of arthritis may affect any joint including large joints, fingers and toes and spine.
Diagnosis of this enthesitis associated arthritis can be difficult since the skin psoriasis rash typically appears after the psoriasis.
Nail disease that is linked to enthesitis may also be a feature of this type of arthritis.
In this form of arthritis, joint pain is part of a general illness involving fever, tiredness, rash, loss of appetite and weight loss.
It can be a severe multi organ or what is termed a systemic disease and there is no evidence thus far linking it to enthesitis.
Sometimes patients don't fit into the groups listed above and are termed as undifferentiated arthritis.
Some of these may develop psoriasis of inflammatory bowl disease at a later stage which clearly points to enthesitis.
This is a type of JIA that follows infection and is clearly linked to enthesitis in adults.
Chronic cases are associated with the HLA-B27 gene that is known to be linked to enthesitis in children and adults.
Ultrasound scanning may pick up the enthesitis associated disease.
Magnetic Resonance Imaging may be used to diagnose disease also.
There is a great need to apply imaging to better understand JIA.
A number of mechanically induced enthesopathies can cause diagnostic confusion in JIA.
This is now understood much better since it is known that joint loading or mechanics plays a big role in any disorder of the enthesis including JIA or other entities.