Systemic polyarthritis is a special case of systemic arthritis. Systemic arthritis is a less common and more severe form of juvenile idiopathic arthritis affecting children under 16 years old. It constitutes of only 10 to 15 percent of children affected by juvenile idiopathic arthritis. Systemic means it affects many parts of the body, rather than just the joints and polyarthritis means it causes arthritis in five or more joints. It can target a child’s internal organs as well as the joints. Systemic arthritis is usually autoimmune, meaning your body’s immune system, which usually protects your health by attacking foreign substances such as bacteria and viruses, mistakenly attacks your joints.
Systemic arthritis occurs in boys and girls equally and frequently starts in children under five years of age. It can cause high, spiking fevers of 103 degrees Fahrenheit or higher, lasting for weeks or even months. It may also cause a rash consisting of pale, red spots on the child’s chest, thighs and sometimes other parts of the body.
This is the most difficult type of childhood arthritis to diagnose as it has similar symptoms to other illnesses such as measles, meningitis and leukaemia. Some children recover after one bout of systemic arthritis and suffer no long-term problems. Others will have repeat flare-ups for several years. Some go on to develop polyarthritis without further fever attacks.