Polyarthritis

Osteoarthritis vs Rheumatoid Arthritis (Top HY)

Overview of RA

Feature	Osteoarthritis (OA)	Rheumatoid Arthritis (RA)
Pathogenesis	🔹 **Mechanical
🔸** wear and tear destroys articular cartilage (degenerative joint disorder)→ Inflammation with inadequate repair (mediated by chondrocytes).	🔹 Autoimmune
🔸 Inflammation induces formation of pannus (proliferative granulation tissue) which erodes articular cartilage and bone. (more on pathogenesis below) 🔽
Predisposing Factors	🔹 Age.
🔹 Female.
🔹 Obesity.
🔹 Joint trauma.	🔹 Female
🔹 Tobacco smoking
🔹 HLA-DR4 (4-walled “rheum”).
🔹 HLA-DRB1.
🔹 Auto antibodies→ Detected by ELLISA
🔸 Rheumatoid factor → IgM antibody targeting IgG Fc region; in 80%.
🔸 Anti-cyclic citrullinated peptide antibody→ more specific.
Presentation	🔹 Joint pain

🔸 Pain in weight-bearing joints after use (e.g., at the end of the day).
🔸 Can have morning stiffness but less than 30 min.
🔸 Improves with rest.
🔸 Asymmetric joint involvement.

🔹Systemic symptoms 🔸 Absent 🔹 Knee cartilage loss begins medially (“bowlegged”). | 🔹 Joint Pain 🔸 Morning stiffness lasting > 1 hour. 🔸 Pain improves with use. 🔸 Symmetric joint involvement. 🔹 Systemic symptoms 🔸 Present→ fever, fatigue, weight loss. 🔹 Extraarticular manifestations common. | | Joint Findings | 🔹 Bone 🔸 Osteophytes (bone spurs). 🔸 Loose bodies. 🔸 Subchondral sclerosis and cysts. 🔹 Joint space 🔸 Joint space narrowing (asymmetric). 🔹 Hand 🔸 Heberden nodes (at DIP) 🔸 Bouchard nodes (at PIP) 🔸 And 1st CMC; not MCP 🔹 Extra 🔸 Synovial fluid noninflammatory (WBC < 2000/mm³) | 🔹 Bone 🔸 Erosions. 🔸 Juxta-articular osteopenia. 🔸 Subchondral cysts. 🔹 Joint space 🔸 Joint space narrowing (symmetric). 🔹 Hand 🔸 Ulnar finger deviation 🔸 Swan neck 🔸 Boutonniere. 🔸 Involves MCP, PIP not DIP or 1st CMC. 🔹 Extra 🔸 Cervical subluxation 🔸 Soft tissue swelling | | Treatment | 🔹 Activity modification. 🔹 Acetaminophen. 🔹 NSAIDs. 🔹 Intra-articular glucocorticoids. | 🔹 NSAIDs. 🔹 Glucocorticoids. 🔹 Disease-modifying agents (e.g., methotrexate, sulfasalazine). 🔹 Biologic agents (e.g., TNF-α inhibitors).

→ DMAs takes time to show relief unlike glucocorticoids (rapid acting). |

<aside> 💡 Extraarticular Manifestations of Rheumatoid Arthritis

Rheumatoid Nodules
- Fibrinoid necrosis with palisading histiocytes
- Located in subcutaneous tissue and lung
- If associated with pneumoconiosis→ Caplan syndrome
Skeletal
- Cervical Subluxation
  - Affect mainly atlantoaxial joint
  - Extension of the neck during endotracheal intubation can worsen the subluxation, leading to acute compression of the spinal cord and/or vertebral arteries → flaccid paralysis with decreased or absent reflexes below the level of the compression
- Carpal Tunnel Syndrome
Respiratory→ Interstitial Lung Disease, Pleuritis
Immunologic→ Sjögren Syndrome, Scleritis
Others→ Pericarditis, Anemia of Chronic Disease, AA Amyloidosis
Neutropenia + Splenomegaly (Felty Syndrome)
- SANTA→ (Splenomegaly, Anemia, Neutropenia, Thrombocytopenia, Arthritis (Rheumatoid) </aside>

<aside> 🧠

Pathogenesis of RA

Activation of T lymphocytes in response to rheumatoid antigens (eg, citrullinated peptides)→ Release cytokines (eg, IL-1, TNF-α) that cause synovial hyperplasia and cartilage destruction → The accelerated metabolic rate of the inflamed synovial tissue leads to local hypoxia → resulting in synovial angiogenesis (neovascularization).
New blood vessels provide nutrients that facilitate expansion of inflamed synovium into a rheumatoid pannus (invasive mass composed of fibroblast-like synovial cells, granulation tissue, and inflammatory cells)→ which can destroy the articular cartilage and underlying subchondral bone.
Ossification of the pannus can lead to fusion of the bones across the affected joint (bony ankylosis) </aside>

Other picture

Pathophysiology of osteoarthritis

     **Pathophysiology of osteoarthritis**

Overlay

Pathophysiology of rheumatoid arthritis

Pathophysiology of rheumatoid arthritis

Overlay

Affected hand joints in RA vs OA

Affected hand joints in RA vs OA

Heberden nodes

       Heberden nodes

Bouchard nodes

       Bouchard nodes

Hand deformities of RA

Hand deformities of RA

Rheumatoid nodules with ulnar deviation

Rheumatoid nodules with ulnar deviation

Other pictures of hand deformities

Seronegative Spondyloarthritis

Overview

Arthritis without rheumatoid factor (no anti-IgG antibody).
Strong association with HLA-B27 (MHC class I serotype).

Common symptoms

Inflammatory back pain→ morning stiffness, improves with exercise
Peripheral arthritis
Enthesitis
- Inflammation at sites of insertion of tendons, ligaments , joint capsules
- Common presentations
  - Achilles tendinitis → posterior heel pain
  - Plantar fasciitis → Plantar heel pain
  - Dactylitis → sausage digits
Dactylitis→ "sausage fingers"
Uveitis

Subtypes (PAIR)

Psoriatic arthritis
Ankylosing spondylitis
Inflammatory bowel disease
Reactive arthritis

Left index finger dactylitis

Left index finger dactylitis

Psoriatic Arthritis

Facts Sheet