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Pathology of Rheumatoid Arthritis
Arthritis rheumatoides
For medical students2 min readUpdated 2026-10-10
Rheumatoid arthritis is a chronic autoimmune disease characterized by progressive destructive synovitis and systemic connective tissue involvement. The pathological process leads to destruction of articular cartilage, joint deformation, and involvement of internal organs.
Key processProliferative synovitis with pannus formation destroying cartilage and bone.
Morphological markerRheumatoid nodule with a zone of fibrinoid necrosis and a palisading cellular rim.
StagesFrom early exudative inflammation to terminal fibrous-bony ankylosis.
Systemic natureGeneralized vasculitis and polyserositis affecting the heart, kidneys, and lungs.
Morphogenesis of Joint Lesions
The disease is based on an immunopathological process affecting the synovial membrane. The main stages include:
Synovitis: characterized by synoviocyte hyperplasia, formation of lymphoid aggregates (CD4+ T cells, plasma cells), and productive vasculitis.
Pannus formation: aggressive granulation tissue that creeps over the cartilage, causing erosion and replacement with fibrous tissue.
Bone changes: development of osteoporosis, formation of subchondral cysts and erosions, ultimately leading to ankylosis.
Stages of Arthritis Development
The process goes through three sequential stages:
Early stage: dominated by edema, hemorrhage, and fibrinoid swelling. "Rice bodies" (necrotic villi) and ragocytes appear in the joint cavity.
Established stage: active proliferation of the pannus, deep destruction of cartilage, formation of erosions and deformations such as ulnar deviation.
Terminal stage: ends with the formation of fibrous-bony ankylosis, leading to complete loss of joint mobility.
Systemic Manifestations (Visceropathies)
In 20–25% of patients, extra-articular changes occur due to connective tissue disorganization:
Rheumatoid nodule: a specific lesion with a center of fibrinoid necrosis surrounded by macrophages and lymphocytes.
Organ involvement: polyserositis, vasculitis, glomerulonephritis, renal amyloidosis, fibrosing alveolitis, and myocarditis frequently develop.
Immune system: lymph node and splenic hyperplasia with marked plasmacytosis is characteristic.
What are ragocytes, which appear in the joint in the early stage of rheumatoid arthritis?
Ragocytes are neutrophils in the serous effusion of the synovial fluid containing rheumatoid factor. These cells are characteristic of the first (early) stage of rheumatoid arthritis. Ragocytes release inflammatory mediators.
What types of finger deformities develop in the established stage of rheumatoid arthritis?
In the established and final stages of rheumatoid arthritis, the following typical finger deformities develop:
Ulnar deviation — deviation of the fingers toward the ulna, resembling a "walrus fin".
Boutonnière deformity — flexion at the proximal interphalangeal joint and hyperextension of the distal interphalangeal joints.
Swan-neck deformity — flexion contracture of the metacarpophalangeal joints, hyperextension of the proximal interphalangeal joints, and flexion of the distal interphalangeal joints.
Lorgnette (telescoping) deformity — severe flexion contracture with multiple subluxations.
Z-shaped (zigzag) deformity of the thumb — subluxation at the interphalangeal joint.
What is rheumatoid factor and to which immunoglobulin class does it most often belong?
Rheumatoid factor is an autoantibody directed against the Fc fragment of immunoglobulin G (IgG). Most commonly, rheumatoid factor belongs to the IgM isotype; IgG, IgA, and IgE isotypes are less common. In the synovial membrane, plasma cells produce rheumatoid factor, and these antibodies interact with each other (with one acting as an antigen), which sustains inflammation in rheumatoid arthritis.
What is the clinical and morphological triad characteristic of Felty syndrome?
Felty syndrome is characterized by the following symptom complex developing against the background of long-standing seropositive rheumatoid arthritis:
Severe joint disease.
Persistent granulocytopenia — less than 2,000/mm³.
Splenomegaly — enlargement of the spleen.
The syndrome is accompanied by a high risk of infections.
What are "rice bodies"?
These are dense aggregates formed in the joint cavity from synovial villi that have undergone fibrinoid necrosis.
What is the role of the pannus in pathogenesis?
The pannus is a layer of granulation tissue that actively destroys and replaces articular cartilage, leading to erosions and subsequent ankylosis.
Which renal changes are most dangerous?
The most serious complication is renal amyloidosis (deposition of AA amyloid), which can lead to chronic kidney disease.
Go deeper
Immunohistochemical composition of lymphoid aggregates in the synovium.
Mechanisms of secondary amyloidosis development in rheumatoid arthritis.
Differential diagnosis of rheumatoid nodules and rheumatic granulomas.
Pathogenesis of vasculitis in systemic manifestations of the disease.
Features of cardiac conduction system involvement in rheumatoid arthritis.