In gouty arthritis, the joint can become red, swollen and extremely tender to the touch. Typically, even a bed sheet brushing against the joint will trigger intense pain. However, gout is characterized by too much uric acid in the blood and tissues.

Inflammatory erosive osteoarthritis (IEO) can look similar to rheumatoid arthritis, in that the inflammatory process is taking place in the body. Over time, there is damage to the joint, which can be seen as erosion on an x-ray. Unlike RA, however, eventually inflammation will subside.

Ankylosing spondylitis (AS) is a form of arthritis that mainly affects the lower back. It causes inflammation and damage at the joints, and first affects the sacroiliac joints between the spine and the pelvis. AS is three times more common in men, and inflames where the tendon inserts into bone, rather than the membrane that lines the joint as in RA.

Lupus is a chronic autoimmune disease in which the body's antibodies attack one's own tissues. Symptoms include skin rash, pain and swelling in joints, muscle aches and fatigue. Sometimes people can develop rheumatoid arthritis and lupus, which can make diagnosis of both conditions a challenge.

Fibromyalgia is a chronic pain condition characterized by widespread pain in the muscles and soft tissue. Similar to RA, fatigue and sleep disturbances are also common. For many years, Fibromyalgia was thought to be a musculoskeletal disorder, however, it is now better defined as a central nervous system disorder resulting in abnormal pain processing.

Lyme disease is an inflammatory disease spread through a tick bite. Symptoms can include flu-like symptoms, joint inflammation, stiff neck and itching. A blood test can be done to check for antibodies to the bacteria that cause the disease.

Autoimmune diseases like rheumatoid arthritis are notoriously difficult to diagnose, especially in the early stages of the illness. A number of other types of inflammatory arthritis have symptoms that are similar to RA. Blood tests offer some help, but diagnosis often depends on the disease progressing enough for symptoms to clarify, as well as on the experience of the rheumatologist.

Pronounced SOO-doe-gout, this condition comes on suddenly, with swelling, warmth, and intense pain in one or more joints, most commonly in the knees. These flares can last for weeks or months. Another name for this disease is calcium pyrophosphate deposition disease. The cause of both gout and pseudogout are deposits of crystals within the joint, but the types of crystals are different in the two diseases. Blood tests and x-rays can identify the presence of these crystals in the joint.

Juvenile idiopathic arthritis (JIA) is the most common form of juvenile arthritis. There are seven subtypes of JIA, differentiated by how many joints are affected, positive or negative rheumatoid factor, systemic involvement, and other factors. Some forms of JIA can present similar to rheumatoid arthritis. The age of the individual is a key factor in diagnosis. If younger than 16, the diagnosis may be JIA. For those who are older than 16, the diagnosis may be rheumatoid arthritis.

Also known as palindromic arthritis, this condition involves inflammation in joints, tissue, or muscles. Episodes can last a few hours or several days and maymove from one joint to the other. Once the swelling and inflammation disappear, joints go back to normal without damage. This helps to distinguish it from rheumatoid arthritis. A significant number of people who have palindromic rheumatism may go on to develop RA.

Mixed Connective Tissue Disease has symptoms of several other conditions, especially lupus, polymyositis, and scleroderma. It is characterized by fatigue, feeling unwell, swelling in the fingers, sometime extreme, muscle pain, and swelling and pain in the joints. In some cases, this can lead to deformities similar to those that can happen in rheumatoid arthritis.

Reactive arthritis is a rare autoimmune disease that develops as a response to an infection. These infections are most commonly gastrointestinal, urinary, or genital. The joints involved are usually knees and the joints in the feet, but the inflammation can also affect your skin, eyes, and urethra. Reiter’s Syndrome is a particular subtype of reactive arthritis, affecting the eyes and urethra in addition to the joints. Symptoms usually disappear within a year.

The Chickungunya virus is spread by mosquitoes and most often occurs in the Caribbean, Africa, India, and South and Central America. It has been identified in the US, as well. Chickungunya starts with high fevers, rash, and severe pain in the joints. The fever and rash usually disappear in 7 to 10 days, similar to a flu, however, the joint pain often lasts between 12 and 15 months. Some patients have joint pain for three years, which can present similar to rheumatoid arthritis.

Still’s Disease usually starts with a salmon-colored rash that doesn’t itch and waves of a high fever, with joint pain appearing a few weeks after the initial symptoms. Still’s Disease is a rare type of inflammatory arthritis which is similar to rheumatoid arthritis. In individuals younger than 16, it is known as Systemic-Onset Juvenile Idiopathic Arthritis, but Still’s Disease can also appear in adults.