Rheumatoid Arthritis (RA)
Definition:
A chronic autoimmune inflammatory disease characterized by symmetrical polyarthritis, primarily involving small joints, with systemic manifestations and progressive joint destruction.
Etiology:
- Multifactorial:
- Genetic predisposition (e.g., HLA-DR4)
- Environmental triggers
- Smoking is a strong risk factor
Pathogenesis:
- Autoimmune response targeting synovial membranes
- Production of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies
- Formation of immune complexes, complement activation, cytokine release → chronic synovitis
- Development of pannus (granulation tissue) → destroys cartilage and bone
- Extra-articular manifestations: nodules, pleuritis, vasculitis, etc.
Clinical Features:
- Symmetrical polyarthritis of small joints (hands, feet), later involving wrists, elbows, shoulders, knees
- Morning stiffness >1 hour
- Fatigue, weight loss, low-grade fever
- Subcutaneous rheumatoid nodules
- Muscle wasting around joints
Diagnosis:
Physical Examination:
- Tender, swollen joints
- Limited range of motion
- Muscle wasting and joint deformity (late stage)
Laboratory Tests:
- Rheumatoid factor (RF): present in ~70%
- Anti-CCP antibodies: more specific, appear earlier
- ESR and CRP: elevated
- CBC: normocytic anemia
Synovial Fluid Aspiration (if effusion present):
- Turbid, high WBC count, low glucose
Imaging:
- X-rays: baseline for joint damage (erosions, joint space narrowing)
- Ultrasound/MRI: early detection of synovitis