Definition

Rheumatoid arthritis (RA) is a chronic autoimmune
disease that causes inflammation and deformity of the
joints. Other problems throughout the body (systemic
problems) may also develop, including inflammation of
blood vessels (vasculitis), the development of bumps
(called rheumatoid nodules) in various parts of the body,
lung disease, blood disorders, and weakening of the
bones (osteoporosis).

Description

The skeletal system of the body is made up of different
types of strong, fibrous tissue called connective tissue.
Bone, cartilage, ligaments, and tendons are all forms
of connective tissue that have different compositions and
different characteristics.

The joints are structures that hold two or more bones
together. Some joints (synovial joints) allow for movement
between the bones being joined (articulating
bones). The simplest synovial joint involves two bones,
separated by a slight gap called the joint cavity. The ends
of each articular bone are covered by a layer of cartilage.
Both articular bones and the joint cavity are surrounded
by a tough tissue called the articular capsule. The articular
capsule has two components, the fibrous membrane
on the outside and the synovial membrane (or synovium)
on the inside. The fibrous membrane may include tough
bands of tissue called ligaments, which are responsible
for providing support to the joints. The synovial membrane
has special cells and many tiny blood vessels (capillaries).
This membrane produces a supply of synovial
fluid that fills the joint cavity, lubricates it, and helps the
articular bones move smoothly about the joint.

In rheumatoid arthritis (RA), the synovial membrane
becomes severely inflamed. Usually thin and delicate, the
synovium becomes thick and stiff, with numerous infoldings
on its surface. The membrane is invaded by white
blood cells, which produce a variety of destructive chemicals.
The cartilage along the articular surfaces of the bones
may be attacked and destroyed, and the bone, articular capsule,
and ligaments may begin to wear away (erode). These
processes severely interfere with movement in the joint.

RA exists all over the world and affects men and
women of all races. In the United States alone, about two
million people suffer from the disease. Women are three
times more likely than men to have RA. About 80% of
people with RA are diagnosed between the ages of 35-
50. RA appears to run in families, although certain factors
in the environment may also influence the development
of the disease.

Causes and symptoms

The underlying event that promotes RA in a person
is unknown. Given the known genetic factors involved in
RA, some researchers have suggested that an outside
event occurs that triggers the disease cycle in a person
with a particular genetic makeup.

Many researchers are examining the possibility that
exposure to an organism (like a bacteria or virus) may be
the first event in the development of RA. The body