Which condition is classified as an autoimmune inflammatory disease?

Rheumatoid arthritis is classified as an autoimmune inflammatory disease because it involves the immune system mistakenly attacking the body's own joint tissues. This chronic condition leads to inflammation of the joints, causing pain, swelling, and potential joint damage. The autoimmune aspect is a key feature, as it distinguishes rheumatoid arthritis from other types of arthritis or pain conditions.

Rheumatoid arthritis is characterized by the presence of autoantibodies in the blood, such as rheumatoid factor and anti-citrullinated protein antibodies (ACPAs), which are indicators of the immune response affecting the joints. This inflammatory process can also have systemic effects, influencing other organs and leading to complications beyond joint pain.

In contrast, conditions like osteoarthritis primarily result from wear and tear on the joints rather than an autoimmune response. Fibromyalgia is a chronic pain syndrome that does not involve joint inflammation and is not classified as an autoimmune disease. Metabolic syndrome is a cluster of conditions related to metabolic risk factors, but it does not involve an autoimmune mechanism either. Thus, rheumatoid arthritis is definitively the correct answer as it uniquely meets the criteria of an autoimmune inflammatory disease.