What is rheumatoid arthritis?
Rheumatoid arthritis (RA) is a chronic autoimmune disease that is systemic but mainly involves the joints. It is marked by inflamed joints with gradual erosion of the articular cartilage with progressive stiffening of the joints over time. However, rheumatoid arthritis being a systemic disease affects several other organs as well such as the skin and blood vessels (second to the joints), heart, lungs and muscles to varying degrees. Although any age group and gender can be affected, it mainly begins within the 40 to 50 year age group and women are three times more likely than men to be afflicted with rheumatoid arthritis.
There are a number of different types of arthritis. Rheumatoid arthritis along with osteoarthritis are the two most common types of arthritis. Whereas rheumatoid arthritis primarily involves the joint lining, osteoarthritis mainly affects the joint cartilage and underlying bone. The term arthritis means joint inflammation. Rheumatoid arthritis is sometimes commonly differentiated as ‘joint arthritis‘ from osteoarthritis which is referred to as ‘bone on bone arthritis‘. However, this should not detract from the fact that rheumatoid arthritis eventually results in erosion of the joint cartilage, damage of the bone and sometimes even fusion of the bones in the joint.
Rheumatoid Arthritis Meaning
Rheumatoid arthritis means that the immune system attacks the joint linings and other tissues in the body. Joints are where two bones meet to articulate with each other. Those joints that have a greater degree of movement have a joint space between the two bones. This joint space is filled with synovial fluid which is produced by the joint lining known as the synovium or synovial membrane. The ends of the bone involved in the joint are capped with articular cartilage that is the actual articulating surface, and not the bone itself. In rheumatoid arthritis, it is primarily this synovium that is damaged by the immune activity but it also affects the inner lining of the blood vessels, cartilage and bone cells of the joint.
In rheumatoid arthritis, different immune cells such as lymphocytes, plasma cells and macrophages infiltrate the synovial lining. A type of lymphocyte known as a CD4+ T-lymphocyte is one of the main cells that are responsible for the disease process in rheumatoid arthritis. It stimulates other immune cells like B-cells to produce immunoglobulins such as rheumatoid factor (RF) and for macrophages to release its inflammatory chemicals. It is these immunoglobulins (antibodies) and inflammatory chemicals (cytokines) that are responsible for directing the immune system to the joint tissues and causing inflammation of the area. The process of inflammation causes swelling, heat, redness and pain at the site.
Rheumatoid Arthritis Causes
Although the disease process (pathophysiology) of rheumatoid arthritis is well understood, the exact cause behind it is not known. Some factor or event serves as a trigger to begin the process in a person who is most likely genetically susceptible to developing rheumatoid arthritis. Theories behind the cause of rheumatoid arthritis includes :
Certain genetic sequences have been identified in rheumatoid arthritis but this is not present in every rheumatoid arthritis patient. It appears that these genes are triggered by certain environmental factors that initiate the inflammation of the synovium and may activate and control those immune cells responsible for the joint inflammation.
Environmental factors may be the trigger for the disease. These factors are broadly referred to as arthritogens. Infectious agents have been implicated as possible arthritogens including certain viruses such as the Epstein-Barr virus (EBV) and bacterial species like Borrelia. However, the role of infectious agent as arthritogens has not been conclusively proven. Other arthritogens are believed to be proteins manufactured in the body in response to certain environmental agents like inhaled toxins which may be seen with cigarette smoking.
Genetic and environmental factors may initiate joint lining inflammation (inflammatory synovitis) but it is only once the immune system becomes disrupted that the inflammatory process can be maintained over the long term. This disruption is known as autoimmunity and means that the immune system attacks the body’s tissues. It is believed that the initial inflammatory synovitis then triggers the autoimmune mechanism which maintains chronic joint inflammation. The immune system forms antibodies, like rheumatoid factor, against the body tissues which helps direct the immune system against the joint structures. Some of the immune cells are able to call up other cells that may then secrete chemicals at the site which promote inflammation.
RA Risk Factors
The exact cause of rheumatoid arthritis remains unknown but certain people seem to be at a greater risk of developing RA. This includes :
- People between 40 to 60 years
- Women are more likely to develop RA
- Those with a family history of RA
- Cigarette smokers
Rheumatoid Arthritis Symptoms
The joints are mainly affected in rheumatoid arthritis.
- Pain (arthralgia), swelling, heat and stiffness of the joints with redness of the overlying skin.
- Morning stiffness of the joints which usually lasts for more than an hour.
- Joint stiffness after a prolonged period of inactivity.
- First the small joints of the hands, wrists and feet are affected but eventually it extends to the larger joints such as the shoulders, elbows, hips, knees and ankles.
- Multiple joints are affected simultaneously (polyarticular).
- Joints on both sides are affected in somewhat the same pattern (bilaterally symmetrical).
Skin and Nodules
Redness of the skin overlying the joint is common. This is known as erythema. It typically presents with heat and tenderness. Almost 1 out of 3 RA patients will develop lumps under the skin (subcutenaous nodules) in the later stages of the disease. These rheumatoid nodules are one of the diagnostic criteria for RA. These nodules can form open sores (ulcers) and secondary bacterial infections may occur at these sites. Red raised plaques, thickening skin, dryness and scaling may be symptoms of psoriasis which along with joint symptoms is known as psoriatic arthritis.
Picture from Wikimedia Commons
Deformities in and around the joint are related not only to the joint structures but also the surrounding tendons, ligaments and even joint capsules. This may present as :
- Flexion contractures
- Radial deviation of the wrist
- Ulnar deviation of the fingers
- Swan neck and Boutonnière deformities
- Synovial cysts which are usually large
Deformed joints typically have no stability and have little to no range of motion.
There are several non-specific systemic symptoms such as :
- Weight loss
Additional symptoms depends on the organs that are affected which may include :
- Muscles and bones (not only the bones of the arthritis joint)
- Heart and coronary arteries
- Lungs, terminal airways and pleural space
- Blood vessels and blood