Refers to all forms of arthritis that begin before the age of 16 years, and persists for more than 6 weeks and are of unknown cause.
It encompasses a group of pediatric inflammatory arthridies that includes: oligoarticular JLA, polyarticular JLA, systemic JLA, psoriatic JLA and enthisitis related arthritis.
Most common chronic rheumatic disease in children.
Prevalence in developed countries between 16 and 150 per 100,000.
The prevalence of JLA is approximately 30 cases per hundred thousand children in Europe and North America, but may be higher in other geographic locations.
Subtype-systemic arthritis-affects males and females equally, accompanied by quotidian fever of at least 2 weeks duration, and may have a non-fixed erythematous rash hepatosplenomegaly, generalized lymphadenopathy or serositis.
Subtype-systemic arthritis-during fever peaks may be associated with abdominal pain or myalgias.
Subtype-systemic arthritis-arthritis is often symmetrical, polyarticular and may develop later in the course of the illness.
Subtype-systemic arthritis-lab abnormalities include anemia, leucocytosis, elevation in the ESR and CRP concentration and thrombocytosis.
Subtype-systemic arthritis-anemia associated with IL-6 induced iron sequestration in the reticuloendothelial system.
Oligoarticular JIA is the most common category of JIA and his characterized by involvement of four or fewer joints in the first six months of disease.
Oligoarticular JIA predominant affects girls between one and five years of age who often have positive ANA tests.
50% of those affected, have monoarthritis, mostly of the knee.
Approximately half of patients with oligoarticular JLA have a persistent course with four or fewer joints involved and a high likelihood of medication induced remission.
The other 50% have extended involvement of multiple joints for six months after disease onset and are less likely to remit.
Chronic anterior uveitis develops in 30% of all patients with oligoarticular JLA.
There does not appear to be an adult onset counterpart of persistent oligoarticular JLA.
First line treatment of oligoarticular JIA involves intra-articular glucocorticoid injections.
Conventional synthetic DMARDS are generally administered if glucocorticoid injections fail to control symptoms or prevent complications.
Nonsteroidal anti-inflammatory drugs are commonly used to relieve muscular scale pain, but most patients require treatment with DMARDS (disease, modifying antirheumatic drugs).
Agents used include tumor necrosis factor inhibitors, Interleukin-1, interleukin-6, and interleukin-17 inhibitors and local intra-articular or intraocular glucocorticoid therapy may be utilized.
Rheumatoid factor negative polyarticular JIA accounts for 15-20% of JIA cases.
The incidence peaks between one and three years and again after eight years.
Most patients are girls presenting with arthritis and involves more than four joints.
Patients with rheumatoid factor negative polyarticular JIA, who are under the age of six are at high risk for the development of chronic anterior uveitis.
With rheumatoid factor negative polyarticular JIA the ANA is positive and up to 50% of patients, but the test for rheumatoid factor is by definition negative.
With rheumatoid factor negative polyarticular JIA there is frequently a relapsing or chronic course.
Treatment is with synthetic DMARD’s such as methotrexate should be initiated soon after the diagnosis of rheumatoid factor negative polyarticular JIA.
Rheumatoid factor positive polyarticular JIA accounts only 5% of JIA cases and is uncommon in children under nine years of age.
The diagnosis requires a positive test rheumatoid factor anti citruliiated protein antibodies are often present.
Rheumatoid factor positive polyarticular JIA can be aggressive and destructive if left untreated.
Therapeutic approaches similar to that for patient with rheumatoid factor negative polyarticular JIA.
Rheumatoid factor negative polyarticular JIA accounts for 15 to 20% of JIA cases.
Like patients with oligoarticular JIA those with rheumatoid factor negative polyarticular JIA, who are under the age of six years are at high risk of the development of chronic uveitis.
The presence of enthesitis, where inflammation at the enthesis where tendons and ligaments attach to bone defines enteritis related arthritis.
Enthesitis and synovitis of peripheral joints often coexist with peripatella and calcaneal entheses most frequently affected.
Enthesitis related arthritis includes juvenile spondyloarthritis and juvenile ankylosing spondylitis.
The clinical manifestations depend on the patient’s age at the onset of disease.
Enthesitis related arthritis is more common in boys than girls and uncommon for the age of six.
Symptomatic axial involvement of the sacrum and inflammatory spine disease or both develop in 40 to 60% of patients, usually during adolescence.
HLA-B27 positivity is associated with more severe disease, sacroiliitis, juvenile ankylosing, spondylitis, and acute anterior uveitis.
Chronic anterior uveitis can lead to blindness and is seen most often in patients with all oligoarticular, rheumatoid factor negative polyarticular, or psoriatic JIA.
The prevalence ranges from 10 to 30% depending upon the JIA category, with girls under the age of six who have positive ANA disease are at highest risk.
Chronic anterior uveitis is less common in older patients and is rare in those with systemic JIA, rheumatoid factor positive polyarticular JIA or enthesitis related arthritis.
Approximately 90% of cases of chronic anterior uveitis occur within four years of the onset of JIA.
The HL a-B 27 molecule probably presents articular antigen to the CD8 positive T cells.
In spondyloarthritis, local T cells and innate immune cell produce IL-17 and TNF alpha, resulting in inflammation of tendons, entheseal fibrocartilage, , subchondral, bone marrow and adjacent synovium:these inflammatory processes lead to pathological bone alterations.