Rheumatoid arthritis

## What is rheumatoid arthritis?

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Rheumatoid arthritis, or RA for short, is a chronic inflammatory disease. It is also thought to be an autoimmune disease. Its exact cause is unknown. It mainly affects the synovium, the membrane surrounding the movable joints of the skeleton. However it can also affect other organs, such as the skin, lungs, nerves, blood vessels and heart. The inflamed membrane eventually forms pannus tissue. This invades the bone and cartilage, damaging and deforming it.

RA mainly affects joints in the wrist (the metacarpal phalangeal and proximal interphalangeal joints), and those in the foot. it also affects the joints of the wrist, elbow, shoulder, neck, jaw, hip, knee and ankle.

In about 10% of cases, the onset of RA is sudden and severe. This is called acute onset.

In 20% of cases, RA develops relatively quickly over a few weeks. This is called sub-acute onset.

In the majority of cases, (approximately 70%), the conditions develop more slowly, over a long period of time. This is called insidious onset.

Incidence

Approximately 0.8% of the U.K.'s adult population have rheumatoid arthritis. other sources have estimated about 400,000 people with the condition in the country.

Approximately 12,000 children under 16 have JIA (Juvenile Idiopathic Arthritis).

It most frequently occurs between the ages of 35 and 45, and affects women more than men, in the ratio of 3:1.

Genetic Factors

Genetic factors have been linked to incidence of rheumatoid arthritis. RA tends to run in families. the condition is often linked with the gene HLA-DR4. However this gene occurs in about 20-30 per cent of the population, and so is thought to make one only more susceptible to an external trigger that sets off the disease.