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Musculoskeletal conditions - arthritis and osteoporosis

Juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is a type of inflammatory arthritis of unknown cause which develops in children 15 years and under. It may also be referred to as juvenile chronic arthritis (JCA), juvenile rheumatoid arthritis (JRA) or simply juvenile arthritis.

JIA is a long-term disease that has minimal impact on the majority of those who develop the condition, but some can be severely affected. A small percentage of children will experience ongoing disability as a result of their condition.

All children with JIA are affected differently. However, a child with JIA is likely to have swollen, painful joints (lasting more than six weeks), which may be stiff and difficult to move. The inflammation of the joints may result in damage to the bone and cartilage, with possible changes in bone growth. The affected bones may become longer, shorter or bigger.

Research has not yet discovered what causes JIA. It is an unpredictable, autoimmune disease in which the immune system (which normally defends the body against foreign matter) becomes confused, and releases chemicals which cause inflammation. The factors that trigger the disease are unknown. Heredity may be a factor, but on its own does not seem to cause JIA. JIA is not contagious.

JIA is not a single condition but a group of conditions with some similar features. There are several different forms of JIA, distinguished by the number and site of joints affected during the first 6 months of onset, and the presence of other symptoms¹. There are three major types of JIA, which have different features:

• Oligoarthritis is the most common form of chronic arthritis in childhood, accounting for over half of all cases. Four or fewer joints are affected following its onset. Children affected are usually aged between 1 and 4 years, with girls affected nearly twice as often as boys. Joint involvement may appear to be random. Most commonly affected are the larger joints such as the knees and ankles but also smaller joints like wrists and elbows. The most common symptoms are morning stiffness and contracture of the affected joints (fibrous tissue causing difficulty in straightening) and, in rarer cases, abnormal limb growth. Prognosis for oligoarthritis sufferers is very good, with up to 80% of cases going into complete remission by adulthood².
  
  
• Polyarthritis, also referred to as polyarticular arthritis (meaning 'many joints'), accounts for approximately one-third of cases of chronic childhood arthritis. Five or more joints are involved in the first 6 months following onset of the arthritis, with joints usually being affected in symmetrical fashion, that is, the same joints on each side of the body. Any joints in the body may be affected. Once again, girls are affected twice as often as boys. Onset is most common in children 6 years and over. In severe cases, joint deformity and disability may occur³.
  
  
• Systemic arthritis (also known as Still's disease) is the least common but most serious form of juvenile arthritis, equally affecting both boys and girls, and generally occurring between 5 and 10 years of age⁴. It accounts for about ten per cent of chronic childhood arthritis. Initial presentation is with a daily spiking fever, which returns to normal between spikes. The fever may be associated with a characteristic salmon pink, non-itchy rash seen on the upper trunk, neck, armpits and thighs. Other symptoms include fatigue, aching limbs, abnormal enlargement of the liver, spleen and lymph nodes, anaemia, and inflammation of the tissues lining the lungs, heart and abdomen. At the beginning, joint disease may be negligible, making diagnosis difficult. Eventually, joint disease may occur in both large and small joints in the body. Systemic arthritis may be long-lasting; however most children recover fully. Only a small number go on to develop a severe disability⁵.

With good treatment, most patients with JIA are able to lead an active life. Deaths due to JIA are rare, but the condition may have considerable effects on quality of life because of the psychological impact of long-term illness, the effects the condition imposes on family life and the side effects of medications used to treat the condition.

¹ Page 41, Arthritis and osteoporosis in Australia 2008, AIHW, December 2008
² Page 42, Arthritis and osteoporosis in Australia 2008, AIHW, December 2008
³ Page 43, Arthritis and osteoporosis in Australia 2008, AIHW, December 2008
⁴ Ibid
⁵ Ibid

Page last reviewed: 23 August 2010