Rheumatoid Arthritis
Pathological Change
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In Rheumatoid Arthritis (RA), the synovium becomes edematous (↑ fluid content, ↓ viscosity), leading to:
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Thickening, then hypertrophy, and finally
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Pannus formation — hallmark of disease involving fibroblasts and small blood vessels.
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General Characteristics
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RA is a non-suppurative chronic disease.
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Symmetrical inflammation of peripheral joints with progressive destruction of periarticular structures.
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Associated with HLA Class II genes: HLA-DR, HLA-DQ.
Most Common Joints Affected
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MCP of index finger > Wrist > PIP > MTP > Knee, Ankle, Shoulder, Elbow.
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DIP joints spared (DIP joints are involved in Osteoarthritis, not RA).
Important Autoantibodies
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Most specific: Anti-CCP antibodies.
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Rheumatoid factor (RF): IgM antibodies directed against Fc portion of IgG.
Common Complications
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Tendon rupture: Extensor digitorum communis (most common).
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Eye complication: Dry eye (Sicca syndrome) — seen in ~38%.
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Lung complication: Interstitial Lung Disease (ILD).
Characteristic Deformities
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Z-deviation of hand:
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Radial deviation at the wrist.
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Ulnar deviation of fingers.
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Swan neck deformity: Hyperextension of PIP, flexion of DIP.
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Hill’s hiker’s thumb:
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Extension at 1st IP joint.
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Flexion at 1st MCP joint.
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Loss of thumb mobility and pinch.
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Hammer toes.
X-ray Findings
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Juxta-articular osteopenia.
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Bone erosions.
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↓ Joint space due to cartilage loss.
Syndromic Associations
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Felty’s syndrome: Chronic RA + Splenomegaly + Neutropenia (<1500 cells/mm³).
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Caplan’s syndrome: Pulmonary nodules + Pneumoconiosis in RA patients.
Treatment
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First-line (DOC): Methotrexate (DMARD).
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Best analgesic: Naproxen.
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Biologics:
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TNF inhibitors: Etanercept, Infliximab, Adalimumab.
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Rituximab (anti-CD20 monoclonal antibody).
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MCQ
Q. Which structure in the joint is affected earliest in Rheumatoid Arthritis?
a. Capsule
b. Articular cartilage
c. Synovium ✅
d. Subchondral bone
