Long term steroid use can cause contribute to the development of cataracts.Macrophage activation syndrome (MAS) is a severe, potentially life-threatening complication that can occur in patients with the systemic subtype of JIA. MAS involves uncontrolled activation of the immune system, sometimes referred to as a cytokine storm, which can present with a sepsis-like picture of fever, rash, enlarged liver and spleen, enlarged lymph nodes and cardiorespiratory compromise. It is recognised by a series of characteristic changes in laboratory parameters, including a high ferritin and a paradoxically low erythrocyte sedimentation rate. Causes
The cause of JIA remains unknown. However, the disorder is autoimmune — meaning that the bodys own immune system starts to attack and destroy cells and tissues (particularly in the joints) for no apparent reason. The immune system is thought to be provoked by changes in the environment, in combination with mutations in many associated genes and/or other causes of differential expression of genes. Experimental studies have shown that certain mutated viruses may be able to trigger JIA. The disease appears to be more common in girls, and is most common in Caucasians.The cause of JIA, as the word "idiopathic" suggests, is unknown and an area of active research. Current understanding of JIA suggests that it arises in a genetically susceptible individual due to environmental factors. Diagnosis
The diagnosis of JIA can be difficult, in part because joint pain in children is so common and may be from many causes other than JIA.
Complications
JIA is a chronic disorder, which if neglected, can lead to serious complications. However, with regular follow-up and modern treatments, complications have reduced and outcomes improved. If inflammation is not treated, it can damage the joint, the cartilage and the bone. With the advent of modern therapies, these complications of JIA have become much less common.Children with JIA may have a reduced overall rate of growth, especially if the disease involves many joints or other body systems. This may be due to a combination of the disease itself, as well as its treatments, particularly corticosteroid use. Paradoxically, limbs where a large joint (such as the knee) is inflamed may have increased growth in the short term, leading to limb-length discrepancy (i.e. one arm or leg is slightly longer than the other). This is due to increased blood supply to the bony growth plates surrounding the inflamed joints. Bone density and bone strength may be reduced through a combination of inflammation, corticosteroid use and reduced physical activity levels. Other musculoskeletal complications may include joint contractures, muscle weakness or muscle wasting.Uveitis, if left untreated, can result in scarring, glaucoma, cataracts, and even blindness. Regular monitoring allows for early detection and treatment. Steroid eye drops are usually the first line treatment for anterior uveitis. However, other treatments – many of which also treat arthritis (e.g. methotrexate, biologics) – may be required to keep the inflammation under control, and to minimise steroid use over the longer term.