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’s normal
response to such an organism is to produce cells that
can attack and kill the organism, protecting the body
from the foreign invader. In an autoimmune disease like
RA, this immune cycle spins out of control. The body
produces misdirected immune cells, which accidentally
identify parts of the person’s body as foreign. These
immune cells then produce a variety of chemicals that
injure and destroy parts of the body.

RA can begin very gradually, or it can strike quickly.
The first symptoms are pain, swelling, and stiffness in
the joints. The most commonly involved joints include
hands, feet, wrists, elbows, and ankles, although other
joints may also be involved. The joints are affected in a
symmetrical fashion. This means that if the right wrist is
involved, the left wrist is also involved. Patients frequently
experience painful joint stiffness when they first get up
in the morning, lasting for perhaps an hour. Over time,
the joints become deformed. The joints may be difficult
to straighten, and affected fingers and toes may be permanently
bent (flexed). The hands and feet may curve
outward in an abnormal way.

Many patients also notice increased fatigue, loss of
appetite, weight loss, and sometimes fever. Rheumatoid
nodules are bumps that appear under the skin around the
joints and on the top of the arms and legs. These nodules
can also occur in the tissue covering the outside of the
lungs and lining the chest cavity (pleura), and in the tissue
covering the brain and spinal cord (meninges). Lung
involvement may cause shortness of breath and is seen
more in men. Vasculitis (inflammation of the blood vessels)
may interfere with blood circulation. This can result
in irritated pits (ulcers) in the skin, tissue death (gangrene),
and interference with nerve functioning that
causes numbness and tingling.

Juvenile RA is a chronic inflammatory disease that
affects the joints of children less than 16 years old. It is
estimated to affect as many as 250,000 children in the
United States alone. Most children with juvenile RA
have arthritis when the illness starts, which affects multiple
joints in 50% of these children, and only one joint in
30%. In all, 20% of the children affected by juvenile RA
have the acute systemic form of the disease, which is
characterized by fever, joint inflammation, rash, liver
disease, and gastrointestinal disease.

Two periods of childhood are associated with an
increased incidence of onset of juvenile RA. The first is
from one to three years of age, and the second, from
eight to 12 years. When more than four joints are affected,
the disease is described as being polyarticular. If less
than four joints are affected, the disease is known as pauciarticular
juvenile RA, and this particular manifestation
falls into two categories. The first occurs in girls aged
one to four years old, and the onset of joint involvement
is in the knees, ankles, or elbows. The second form
occurs in boys aged eight years and older, and involves
the larger joints, such as those of the hips and legs.

Diagnosis

There are no tests available that can absolutely diagnose
RA. Instead, a number of tests exist that can suggest
the diagnosis of RA. Blood tests include a special test of
red blood cells (called erythrocyte sedimentation
rate), which is positive in nearly 100% of patients with
RA. However, this test is also positive in a variety of
other diseases. Tests for anemia are usually positive in
patients with RA, but can also be positive in many other
unrelated diseases. Rheumatoid factor is another diagnostic
test that measures the presence and amounts of
rheumatoid factor in the blood. Rheumatoid factor is an
autoantibody found in about 80% of patients with RA. It
is often not very specific however, because it is found in
about 5% of all healthy people and in 10-20% of healthy
people over the age of 65. In addition, rheumatoid factor
is also positive in a large number of other autoimmune
diseases and other infectious diseases, including systemic
lupus erythematosus, bacterial endocarditis,
malaria, and syphilis. In addition, young people who
have a process called juvenile rheumatoid arthritis often
have no rheumatoid factor present in their blood.
Finally, the clinician may examine the synovial
fluid, by inserting a thin needle into a synovial joint. In
RA, this fluid has certain characteristics that indicate
active inflammation. The fluid is cloudy, with increased
protein and decreased or normal glucose. It also contains
a higher than normal number of white blood cells. While
these findings suggest inflammatory arthritis, they are
not specific to RA.