A number of complications are possible; reduced activity can lead to bones weakened by osteoporosis and spontaneous fractures. Amyloid, an unusual protein, can be deposited in all tissue (amyloidosis), which can reduce kidney function, for example. Disturbances of heart rhythm and lung abnormalities can also occur. In diagnosis rheumatoid arthritis must be distinguished from other rheumatic conditions. Blood tests show rheumatic factors in 80 per cent of patients, but these also occur in some healthy people. Fluid from the joints may be tested, and the joints X-rayed. There is a form of rheumatoid arthritis which occurs in children, called Still’s disease, in which the child usually feels generally unwell and the spleen and lymph nodes swell before arthritis sets in. Treatment of rheumatoid arthritis is usually by rest, above all of the joints. Painkillers may be prescribed, and gold salts and corticosteroids to check inflammation. Drugs to prevent cell division may also be employed. At an early stage the sinovial membrane can be removed by surgery, and in later stages of crippling arthritis major affected joints may be replaced with artificial ones.