Rheumatoid arthritis (RA) is an autoimmune disease that causes inflammation of the joints. Because many symptoms of RA are similar to those of a variety of other diseases, diagnosis can be difficult.A correct diagnosis requires clinical evaluation, X-rays, and a series of laboratory tests.Understanding the type of RA you have will help you and your doctor decide on a course of treatment.ecause many symptoms of RA are similar to those of a variety of other diseases, diagnosis can be difficult. A correct diagnosis requires clinical evaluation, X-rays, and a series of laboratory tests. Understanding the type of RA you have will help you and your doctor decide on a course of treatment.