(originally known as chronic polyarthritis) is an inflammatory joint disease and is one of the autoimmune diseases. The immune system attacks the body's own joint tissue, causing inflammation to the tissue of the joints, which can lead to inflammation, pain, swelling and ultimately joint damage. However, the cause of this is still unknown. Bacterial or viral infections, drugs, toxins, disorders of immune regulation and genetic predispositions have been speculated.

The symptoms are initially unspecific and begin with fatigue, a slight fever and a feeling of heaviness inRheumatoid arthritis the muscles. Only as the disease progresses do the typical symptoms such as swelling and tearing pain in the small joints of the fingers and feet occur. Later larger joints (e.g. knees) can also be affected, and morning stiffness and limited mobility may also develop.