Rheumatoid arthritis in review: Clinical, anatomical, cellular and molecular points of view.

Rheumatoid arthritis (RA) is the most common chronic autoimmune disease of the joints affecting close to 0.5-1.0% of the general population. Although the etiopathogenesis of RA remains elusive, the involvement of dendritic cells and type 17 T-helper cells appears to be pivotal in maintaining a state of chronic inflammation. RA is generally characterized by small joint involvement. A chronic inflammatory process leads to joint destruction and to tendon and ligament laxity and disintegration. These processes result in an imbalance of forces acting on the joints causing joint deformities including swan neck deformity, boutonniere deformity of the hands, flexion deformity of the wrist, lesser toe deformities, and others. In some instances, bony erosions subsequent to the RA disease process can result in life-threatening events including, for example, atlanto-axial subluxation, which can cause myelopathy and paralysis; and basilar invagination, which can cause brain stem injury and imminent death. Although less commonly involved, larger joints are not spared, as evidenced by the involvement of the elbow, hip, and shoulder joints in a sizable proportion of RA patients. The progression and prognosis of this disease entity are variable, guarded and dependent on the efficacy and response to treatment modalities employed. Inadequate management results in disease progression, which ultimately leads to joint erosion, destruction, deformities and substantial decrease in the functional quality of life. Clin. Anat. 31:216-223, 2018. © 2017 Wiley Periodicals, Inc.