Although the primary symptom of rheumatoid arthritis is joint pain and reduced mobility, the dysfunction of the immune system that causes it to attack the joints is not joint-specific—it can cause the immune cells to attack other tissues as well. The other organs most commonly affected are the skin, the lungs, and the blood vessels. Sometimes the heart, brain, and even the cells of the immune system can be affected, causing additional medical problems. But it is rare to suffer from significant non–joint-related symptoms.

The most common symptom of rheumatoid arthritis outside of the joints is the presence of what are called rheumatoid nodules. These are small lumps of soft tissue that can be felt beneath the skin, most commonly over the elbows.

Skin changes

Skin changes may also occur in rheumatoid arthritis because of blood vessel inflammation (vasculitis). Skin changes may include raised, painless red to purple knots on the skin, especially over the legs and arms; painful, red to black areas that look like pimples around the finger and toenails; and rarely, skin ulcers on the lower legs.

Lung problems

As rheumatoid arthritis progresses, lung problems may be experienced as shortness of breath at rest or with exertion, chest pain upon breathing (pleurisy), and dry cough.

Blood vessel problems

The same process that damages the blood vessels (vasculitis) may affect nerves, leading to loss of sensation or strength; the gut, resulting in internal bleeding; the eyes, causing redness, pain, and sometimes loss of vision; and many other organ systems of the body.

Other autoimmune disorders

Rheumatoid arthritis may also be associated with other autoimmune disorders, such as thyroid gland problems, salivary gland inflammation (causing dry eyes and dry mouth, known as "sicca syndrome"), and increased destruction of certain types of blood cells.

Nerve problems

The joint inflammation itself may damage adjacent structures, leading to compression of certain nerves. Carpal tunnel syndrome is one type of nerve damage caused by increased pressure on the nerve.

Spleen enlargement

Felty's syndrome is a rare complication of rheumatoid arthritis in which the spleen is enlarged. There is also increased destruction of particular white blood cells by the immune system. These white blood cells are important in fighting infection. People with Felty's syndrome are more susceptible to certain bacterial and fungal infections.

Non-joint symptoms of rheumatoid arthritis, such as lung, heart, nerve and eye involvement, are relatively uncommon. While rheumatoid arthritis is overall more common among women, non–joint complications occur equally in men and women, indicating that men are at higher risk. The presence of these symptoms may indicate that a person is at risk of developing other rheumatoid arthritis–related problems.

In many ways, the average person may be at greater risk of having problems secondary to arthritis itself rather than as a direct result of the disease process. Arthritis diminishes mobility if not well controlled, leading to general deconditioning, which makes it more difficult for people to get around and lose weight. As people decrease their activities, their symptoms get worse. As they become less active, they may become homebound and sometimes even bed-bound, both of which limit their ability to care for themselves. Some are at greater risk for infections, such as pneumonia, because of diminished mobility and a sedentary lifestyle. Others are at risk for falls due to muscular weakness. With falls comes the risk of fracture and fracture complications. The best way to prevent such complications is to treat the arthritis early and aggressively to help maintain a person's function to the greatest degree possible.