Rheumatoid arthritis (RA) is a chronic inflammatory polyarthropathy with myriad degrees of systemic involvement. The disease is multifactorial, and the clinical picture varies widely in severity, extent of involvement, and symptoms. The capricious course of the disease may be persistent and debilitating or relapsing and remitting. With each successive exacerbation, new joints may become involved.
Rheumatoid arthritis is the most common form of inflammatory arthritis, affecting approximately 0.8% of the U.S. population. The onset of RA can occur at any age, but most cases are diagnosed in patients between the ages of 35 and 50 years. RA is two to three times more likely to develop in women than in men. Patients with RA have a reduced life expectancy ranging from 3 to 7 years.
The exact cause of RA remains elusive, but heredity plays some role in increasing a person’s susceptibility. Impaired immunity, stress, and other environmental factors may precipitate or aggravate the disease.
A viral or a bacterial infection that alters the immune system in a genetically susceptible host may play a role in the etiology. The invading microbe may produce a protein similar to those in the body’s own tissue, particularly joint tissue (molecular mimicry). To destroy the antigen, the immune system may mount an autoimmune response and mistakenly direct its attack against its own tissue. Circulating autoantibodies called rheumatoid factors are detectable in 70% to 80% of patients with RA.
Inflammation and destruction of synovial tissues are responsible for most of the symptoms and chronic disability associated with RA. Joint involvement progresses in three main stages: (1) inflammation of the joint synovial membrane and infiltration by polymorphonuclear leukocytes; (2) rapid division and growth of cells in the joint (synovial proliferation and pannus formation); and (3) liberation of osteolytic enzymes, proteases, and collagenases, which damage small blood vessels, cartilage, ligaments, tendons, and bones. Collapse of normal cortical and medullary architecture leads to erosion and dislocation of bone that is contiguous with the inflammatory cell mass.
The onset of symptoms is most often insidious, evolving over a period of weeks to months. The most common sites of onset are the hands, wrists, and feet. There is often symmetric joint involvement. Swelling, warmth, and pain in the affected joints are caused by the inflammatory process. Morning stiffness, weight loss, and fatigue are noted early in the disease course.
Dissolution of bone and disuse atrophy of bone (osteoporosis) are found in all seriously affected areas. Pain, inflammation, and erosion of bone and tissue may permanently limit the joint’s full range of motion. Later stages of the disease are characterized by severe pain, joint instability, and crippling deformities. Nerve entrapment may occur at any site where peripheral nerves pass near the inflamed joint. Carpal tunnel syndrome is a common peripheral neuropathy.
Synovitis in the temporomandibular joint may limit jaw motion. An estimated 30% to 70% of patients with RA have involvement of the temporomandibular joint. As the disease progresses, flexion contractures and soft tissue swelling may lead to a marked limitation in the patient’s ability to open the jaw.
Although the thoracic and lumbar spine are usually spared, involvement of the cervical spine may be extensive and can lead to limited movement or deformity of the neck and to severe laryngeal deviation.
The most common site of cervical spine synovitis is C1 to C2. Atlantoaxial (C1–C2) instability results from erosion and collapse of bone and from destruction of supporting cervical ligaments. Symptoms occur when excessive motion between C1 and C2 exerts pressure on the spinal cord. Additionally, separation of the atlanto-odontoid articulation may allow the odontoid process of the axis to impinge on the spinal cord, leading to neurologic damage. The atlantoaxial subluxation may also exert pressure and impair blood flow through the vertebral arteries.
Arthritis extends to the cricoarytenoid joint of the larynx in 40% of patients with severe RA. The joint may become swollen, inflamed, and fixed in a position that obstructs air flow. Vocal cord nodules and polyps may also be present. Symptoms of cricoarytenoid arthritis include tenderness over the larynx, hoarseness, pain on swallowing with radiation to the ear, and dyspnea or stridor. Patients with no overt clinical symptoms may also have significant laryngeal disease.