A chronic inflammatory disease of variable severity that affects the joints and may involve the connective tissues and viscera.
Juvenile Rheumatoid Arthritis (JRA); Still Disease; Still-Chauffard Disease. The International League of Associations of Rheumatologists Task Force on the Classification of Childhood Arthritis has proposed that the previously used terminology of JRA be discarded and replaced by the umbrella term Juvenile Idiopathic Arthritis (JIA).
Approximately 10-20:100,000 children are affected. A particularly high incidence has been described in Native Americans and in parts of Scandinavia. No sexual predilection exists; however, the oligo- and polyarticular forms tend to be more common in girls, whereas the systemic-onset form of the disease affects both genders equally. Rheumatoid factor (RF)-positive polyarthritis accounts for a less common JIA-subtype.
An increased susceptibility has been reported in association with polymorphisms in the IL6 (Interleukin-6) gene located chromosome 7p15.3 or in the MIF (Macrophage Migration Inhibitory Factor) gene mapped to chromosome 22q11.23. In addition, an association with particular HLA haplotypes (eg, HLA-B27) has been observed.
The disease is caused by chronic synovial inflammation of unknown origin characterized by B-lymphocyte infiltration. Synovial proliferation seems to be the result of cytokines released by invading macrophages and T-cells. Lymphocytic infiltration has been suggested to induce angiogenesis, thereby maintaining the disease process. Destruction of the joint cartilage and, later, of the bone is caused by the pannus.
The previous American College of Rheumatology classification of JRA referred to oligoarticular arthritis, polyarticular arthritis, or systemic illness of at least 6 weeks’ duration. The current classification outlines seven disease categories based on the clinical and laboratory features present in the first 6 months of the illness, and defines JIA as an arthritis occurring before the age of 16 years, and lasting for at least 6 weeks without an established cause. The diagnosis is made by exclusion of other potentially similar clinical conditions (eg, malignancy or infection). The clinical course is highly variable from resolution after a single episode to chronic systemic disease with frequent articular flare-ups.
The polyarticular form of JIA may occur in children at any age. The oligoarticular and the systemic-onset forms usually occur in early childhood, although later onset (including adolescence) has been described. Skeletal features include generalized osteopenia, joint involvement, either oligoarticular (1-4 joints, also called pauciarticular) or polyarticular (≥5 joints), with cartilage destruction preceding the bony involvement. Effusions in affected joints and radial deviation of the wrist may occur. Joint inflammation may be associated with muscle atrophy. Bony fusion of the cervical spine is common and most frequently occurs at the C2-C3 level secondary to apophyseal ankylosis. Atlanto-odontoid instability may occur secondary to pannus ...