Rheumatoid Arthritis (RA): Pathological Essentials
Rheumatoid Arthritis is a chronic, systemic, inflammatory autoimmune disorder that primarily affects the synovial lining of joints. It is characterized by symmetric polyarthritis and significant joint destruction over time.
1. Pathogenesis and Morphology
The hallmark of RA is the development of the Pannus—a hyperplastic synovial tissue mass consisting of activated synoviocytes, fibroblasts, inflammatory T-cells, B-cells, and plasma cells. This pannus invades cartilage and subchondral bone, leading to joint destruction.
| Marker/Feature | Clinical/Pathological Significance |
|---|---|
| Rheumatoid Factor (RF) | IgM antibody directed against the Fc portion of self-IgG. Sensitive, but non-specific. |
| Anti-CCP | Anti-cyclic citrullinated peptide. Highly specific for RA; predictive of more aggressive joint damage. |
| HLA Association | HLA-DR4 (Strong genetic predisposition). |
2. Clinical and Systemic Manifestations
- Joint Involvement: Symmetric polyarthritis affecting small joints (MCP, PIP). Sparing of the DIP joints (a key differentiator from osteoarthritis).
- Morning Stiffness: Lasts >1 hour and improves with use.
- Deformities: Ulnar deviation of fingers, boutonniere deformity, and swan-neck deformity.
- Rheumatoid Nodules: Fibrinoid necrosis surrounded by palisading macrophages. Typically found on extensor surfaces.
3. High-Yield Syndromes & Complications
Felty Syndrome: Defined by the triad of Rheumatoid arthritis, Splenomegaly, and Neutropenia. High risk of recurrent bacterial infections.
- Secondary Amyloidosis: Chronic systemic inflammation leads to the deposition of Serum Amyloid A (SAA) protein in the kidneys, causing nephrotic syndrome.
- Caplan Syndrome: A combination of rheumatoid arthritis and pneumoconiosis (coal workers’ lung) with intrapulmonary nodules.
- Atlantoaxial Subluxation: A critical, life-threatening cervical spine complication in severe cases, particularly relevant during endotracheal intubation.