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Juvenile idiopathic arthritis (AIJ)

Artritis idiopàtica juvenil

Juvenile idiopathic arthritis is a chronic disease characterised by persistent inflammation of the joints, which manifests before the age of 16. 



There are different types of multifactorial juvenile idiopathic arthritis. They are distinguished by the joints affected and the other symptoms that appear, such as fever and skin lesions. It is a chronic disease with symptoms that can persist until adulthood.


The symptoms 

The main symptoms are pain, inflammation and joint warmth, combined with rigidity and mobility difficulties. This disease can appear slowly and progressively. When small children have this disease they may feel tired and be irritable. Older children may notice rigidity when they move their joints when they get up in the morning. 

Onset of the disease can occasionally be sudden, acute and serious. The disease can present with other symptoms, such as a general unwell feeling, fever, skin blemishes or inflammation of various joints. 


Whois affected by the disease

Juvenile idiopathic arthritis is a disease with a huge variety of types:

  • Oligoarticular AIJ
  • Rheumatoid factor-negative polyarticular AIJ
  • Rheumatoid factor-positive polyarticular AIJ
  • Systemic AIJ
  • Enthesitis-related AIJ
  • Psoriatic AIJ
  • Undifferentiated AIJ

1 or 2 children in a thousand suffer from this disease. 



Juvenile idiopathic arthritis is diagnosed in the under-16s when the symptoms are present for more than 6 weeks and other illnesses that can cause arthritis have been ruled out. The diagnosis is made based on each patient's medical history, a physical examination and blood tests. 


Typical tests

Blood tests, examination of the joints and eye tests are carried out at the time of diagnosis. These help to define the type of idiopathic arthritis more accurately and to predict which patients may develop complications. One example is chronic iridocyclitis, a disease that causes inflammation of the iris. 

Analyses and x-rays are done to evaluate whether the immune system has been altered by the inflammations.

The tests analyse:

  • The rheumatoid factor: allows an autoantibody to be detected which, if present at a high concentration, indicates a subtype of juvenile idiopathic arthritis.
  • Antinuclear antibodies: usually positive in tests on patients with early onset oligoarticular juvenile idiopathic arthritis. These patients are at greater risk of developing chronic iridocyclitis (inflammation of the iris), so must be given eye examinations every 3 months. 
  • HLA-B27 is a cell marker that can be positive in up to 80 % of patients with arthritis associated with an enthesitis, or inflammation of the area where a tendon, muscle or ligament is inserted into the bone. However, it is only positive in 5-8% of healthy people.
  • Last, it is useful to know the globular sedimentation or the C-reactive protein rate as these measure the degree of general inflammation.

Decisions regarding diagnosis and treatment are based more on the symptoms that appear than on the analytical tests.  

Depending on the treatment, patients may need regular analyses (such a blood tests, liver function analyses, or urine analyses) to check for the presence of side effects and to study whether the medicine is toxic, even when there are no symptoms.  

The clinical exploration enables the joint inflammation to be evaluated, although image tests like ultrasounds are sometimes needed. Regular X-rays or MRI scans can be useful to evaluate bone health and growth and to thereby adapt the treatment. 


Standard tests 

When the patient is diagnosed, analytical studies, joint tests and eye exams are also carried out. This helps to better define the exact type of idiopathic arthritis and to predict which patients may develop complications. One example is chronic iridocyclitis, a disease that causes inflammation of the iris.

The tests analyse:

  • Rheumatoid factor: the test detects this autoantibody which, if positive and found in high concentrations, indicates a subtype of juvenile idiopathic arthritis.
  • Antinuclear antibodies: tests for these are often positive in patients with early-onset oligoarticular juvenile idiopathic arthritis. These patients are at increased risk of developing chronic iridocyclitis (inflammation of the iris) and should therefore be scheduled for eye exams every three months. 
  • HLA-B27 is a cellular marker thatis positive in up to 80% of patients with arthritis associated with enthesitis, the inflammation of the bone attachment site of a tendon, muscle or ligament. In contrast, it is only positive in 5-8% of healthy people.
  • Finally, it is useful to know the erythrocyte sedimentation rate, or C-reactive protein, as this measures the degree of general inflammation.

Diagnostic and treatment decisions tend to be based more on the symptoms that appear rather than the analytical tests. 

Depending on the treatment, patients may need periodic tests (such as haemograms, liver function tests, or urine tests) to check for side effects and assess whether a drug is toxic, even if there are no symptoms. 

Clinical examinations can assess joint inflammation, although imaging tests, such as ultrasound scans, are sometimes necessary. Periodic X-rays or MRI scans can be helpful in assessing bone health and growth and in personalising the treatment. 


 Typical treatment 

It is important to start treatment as soon as possible to minimise the pain, prevent joint deformities and ensure correct growth. Each child responds differently to the disease and treatment, thereby requiring the full cooperation of the child and their family. Emotional support needs to be provided to ensure that the treatment plan is followed right from the start because this is a chronic disease and it is vital to take the medication, do the recommended exercise and follow a healthy diet. The treatment will depend on the type, the stage and the severity of the illness. The aim is to look after the physical and psychological development of the child to try to improve their quality of life.

Consistent effort and collaboration between the child and their family and the specialists is required to ensure that there are no after-effects, or to minimise them. It is essential that the family is well informed about the disease and that the child understands it in a way that is consistent with their age.


Departments related to treating this desease

 Management of paediatric and adult patient cases 93 489 30 00 (ext. 6330 or 4697)

More information at: or Citizens advice: 93 489 34 15


Associations of patients with which the Autoinflammatory Diseases Unit collaborates

  • Autoinflammatory Syndrome Association of Patients affected by Criopirinopathy
  • Catalan Rheumatology League FEDER
  • Spanish Catalonia Familial Mediterranean Fever Association (FMF)
  • Spanish Familial Mediterranean Fever Association.

Hospital o serveis complementaris relacionats

Traumatology, Rehabilitation and Burns Hospital

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