Clinical Significance Of Rheumatoid Arthritis: Etiology, Pathology And Clinical Presentations
Womans Feet With Rheumatoid Arthritis
Etiology And Pathology
Rheumatoid arthritis is a generalized symmetrical polyarthritis clinically characterized mainly by peripheral, symmetrical joints lesions. The disease process may involve other organs like lungs, liver, heart, nerves and the eyes and hence the disease is termed rheumatoid state or rheumatoid disease. Though the vast majority of cases are chronic, some present as acute disease.
Since the exact cause is unknown, various hypothesis have been advanced. These include autoimmune processes and viral infections are triggering factors. Higher prevalence among subjects with HLA DWR4 suggests a genetic predisposition. Such subjects develop antibodies (IgM or IgG) on microbial or other challenge. These antiglobulin antibodies (rheumatoid factor) complex with native IgG, and activate complement to release lysosomal enzymes from synovial leukocytes and elicit a type III immune response. The same mechanism operates in other tissues as well.
Most marked changes are seen in the joints, synovium shows fibrinoid degeneration surrounded by infiltration with fibroblasts and mononuclears. The synovial membrane is thickened, hyperemic and edematous. It proliferates to form villi which invades the articular cartilage to form a pannus. The articular cartilage is eventually destroyed with loss of join space. Fibrosis develops across the joint space to produce ankylosis. The joint deformed and secondary degenerative changes develop. Infection may supervene in these joints to convert them into pyoarthroses.
Extra-articular lesions:Other tissues are affected to varying degress. Basic pathology is the same as in the synovium. Lesions are seen in the skin, lungs, heart, liver, nervous system, and eyes. The small blood vessels may be affected. They show intimal hyperplasia, perivascular round cell infiltration and occasionallt necrotizing panarteritis. These are seen in the malignant form of rheumatoid arthritis.
Knees With Rheumatoid Arthritis
Rheumatoid Arthritis In Joints
Females are affected more than males in a ration of 3:1. The disease is more common in the fourth and fifth decades. Early symptoms are nonspecific and they include undue fatigability, weight loss, poor appetite, transient myalgias and paresthesia.
Articular involvement: The onset is generally insidious and the disease presents as a chronic symmetrical poluarthritis. Less common presentations include:
- Acute polyarthritis;
- Acute monoarticular arthritis
- Chronic monarticular arthritis; or
- Systemic illness with fever, sweating, leukocytosis and pleural effusion.
Any diarthrodial joint may be inflamed. Arthralgia, arthritis, muscle wasting, tendinitis, tendon rupture and deformities constitute the main lesions. The affected joints are warm, painful and swollen. Movements are restricted, especially in the morning (morning stiffness). Classical lesions are in the joints of the hands and feet. Metacarpophalangeal, metatarsophalangeal and proximal interphalangeal joints are inflamed. Wasting of the small muscles of hand may develop due to disuse. In the hands, there is the typical ulnar deviation of the metacarpophalangeal joints. Sometimes there is anterior subluxation of metacarpal heads and medial dislocation of the extensor tendons. Swan neck deformity of the fingers consists of hyperextension of the proximal interphalangeal joints. The deformity impairs effective hand grip. Sometimes the extensor expansion overlying the proximal interphalangeal joint ruptures resulting in the dorsal protrusion of the head of the proximal phalanx. This leads to flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint (boutonniere-button hole) deformity.
The extensor tendons may undergo attrition, these result in loss of extension of the fingers (dropped fingers). The thumb may show a ‘Z’shaped deformity (hitch hiker’s thumb). Large joints like the knees, wrists, ankles, elbows and shoulders may also be involved. Tense synovial effusions may develop in the knees. Baker’s cysts are tense cysts developing in the popliteal fossae as a result of collection of synovial fluid. These may occasionally rupture giving rise to a painful and tender swelling on the calf.
Lateral subluxation of the knee joint is also very common. Chronic arthritis develops which leads to permanent deformities. Deformities are also common in the feet. Hammer toe is flexion at the proximal interphalangeal joint and hyperextension at the metatarsophalangeal joint. Hallux valgus (lateral deviation of the big toe) may develop. The arches of the feet may be lost due to affection of the joints and ligaments. Callosities develop over prominent bony points.
Less commonly, the cervical spine and temporo-mandibular joints are affected, but when they occur, the lesions are characteristic. At the atlanto-axial joint, the transverse ligament of the atlas may be weakened leading to atlanto-axial subluxation. This leads to pain in the neck and pain referred to the temporal and retro-orbital regions. There may also be a “clunking sound” in the neck on flexion. It is dangerous to manipulate the neck to elicit this sign. Atlantoaxial subluxation produces a host of neurological manifestations.
The risk of sudden compression of the spinal cord is high in such subjects. Hence tracheal intubation and similar procedures which require manipulation of the neck should be done only with caution. Temporo-mandibular arthritis leads to pain on mastication. Other portions of the spine such as the dorsolumbar regions and sacroiliac joints are usually not affected.
© 2014 Funom Theophilus Makama