Arthritis

Rheumatoid arthritis, the most common type of inflammatory arthritis, is characterized by persisting inflammatory synovitis resulting in joint damage and systemic reactions, although it can vary in its severity and general effects (Scott et al.; Sewell).

Causes and disease mechanisms. The cause of rheumatoid arthritis is unknown, but is variously attributed to autoimmunity, bacterial infection, Figure 1 How joints are affected by arthritis. SOURCE: Drawing by Hans and Cassidy for the Gale Group. or viral infection. The synovium is infiltrated with white blood cells called lymphocytes, which are seen where inflammation is chronic. Synovial cells proliferate and blood vessels increase markedly. Synovial fluid contains many white blood cells known as polymorphonuclear leukocytes. There are accompanying destructive changes in joint cartilage and bone.

Rheumatoid arthritis is associated with rheumatoid factor production. Several different immunoglobulin classes can be involved, especially IgM and IgA. A minority of cases remain seronegative. Rheumatoid arthritis has a genetic component. It involves three times more women than men, its prevalence increases with age, and it involves 0.25–1 percent of adults and 3–5 percent of elderly women.

Clinical features. The onset of rheumatoid arthritis is usually insidious over several months, though some cases have an acute onset. Characteristic features are joint pain, swelling, and morning stiffness lasting several hours. Typically it involves small joints of the hands and wrists in a symmetrical distribution. Large joint involvement indicates severe disease. In early disease the findings are subtle, while in late disease there Figure 2 The normal knee joint SOURCE: Author are obvious changes, such as the self-descriptive swan-neck and "boutonnière" deformities in the fingers. Large joint damage causes immobility and disability.

Features apart from joint inflammation (extra-articular features) are common. Rheumatoid nodules at sites like the elbow indicate severe, rheumatoid factor–positive disease. Other extra-articular features include dry eyes and dry mouth (Sjögren's syndrome), leg ulcers, nerve damage, lung disease, and inflammation of the pericardium, sclera, and blood vessels.

Investigations. Blood tests are usually abnormal. Rheumatoid factors are antibodies produced by the individual against constituent proteins (auto-antibodies). They bind to one end of normal immunoglobulin, the Fc portion. They occur in about two-thirds of cases, as well as in other disorders with persisting immune inflammation and in many healthy individuals. Other abnormalities reflect the systemic inflammatory response. The erythrocyte sedimentation rate is elevated. Specific measures of acute inflammation, such as C-reactive protein, are also elevated. By contrast hemoglobin levels can be low.

Juxta-articular erosions, a key diagnostic finding, are next to the joint on X-rays of the hands and feet. Other changes are osteoporosis around the joints and loss of joint space. In late disease there is destruction and ankylosis (fusion of the joint due to bone growth). Scintigraphy shows increased blood flow around involved joints in early disease, though such findings are not specific.