Page 510 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

466 section iii Musculoskeletal, skin, and connective tissue ` pathology Musculoskeletal, skin, and connective tissue ` pathology

Osteoarthritis vs rheumatoid arthritis
Osteoarthritis Rheumatoid arthritis
pathogEnEsis Mechanical—wear and tear destroys articular Autoimmune—inflammation A induces
cartilage (degenerative joint disorder) formation of pannus (proliferative granulation
Ž inflammation with inadequate repair. tissue), which erodes articular cartilage and
Chondrocytes mediate degradation and bone.
inadequate repair.
pREdisposing FaCtoRs Age, female, obesity, joint trauma. Female, HLA-DR4 (4-walled “rheum”),
smoking. ⊕ rheumatoid factor (IgM antibody
that targets IgG Fc region; in 80%), anti-cyclic
citrullinated peptide antibody (more specific).

pREsEntation Pain in weight-bearing joints after use (eg, Pain, swelling, and morning stiffness lasting
at the end of the day), improving with rest. > 1 hour, improving with use. Symmetric
Asymmetric joint involvement. Knee cartilage joint involvement. Systemic symptoms
loss begins medially (“bowlegged”). No (fever, fatigue, weight loss). Extraarticular
systemic symptoms. manifestations common.*
Joint Findings Osteophytes (bone spurs), joint space narrowing, Erosions, juxta-articular osteopenia, soft tissue
subchondral sclerosis and cysts. Synovial swelling, subchondral cysts, joint space
fluid noninflammatory (WBC < 2000/mm ). narrowing. Deformities: cervical subluxation,
3
Development of Heberden nodes B (at DIP) ulnar finger deviation, swan neck D,
and Bouchard nodes C (at PIP), and 1st CMC; boutonniere E . Involves MCP, PIP, wrist; not
not MCP. DIP or 1st CMC.

tREatmEnt Activity modification, acetaminophen, NSAIDs, NSAIDs, glucocorticoids, disease-modifying
intra-articular glucocorticoids. agents (eg, methotrexate, sulfasalazine),
biologic agents (eg, TNF-α inhibitors).
*Extraarticular manifestations include rheumatoid nodules (fibrinoid necrosis with palisading histiocytes) in subcutaneous
tissue and lung (+ pneumoconiosis Ž Caplan syndrome), interstitial lung disease, pleuritis, pericarditis, anemia of chronic
disease, neutropenia + splenomegaly (Felty syndrome), AA amyloidosis, Sjögren syndrome, scleritis, carpal tunnel syndrome.
Osteoarthritis Normal Normal Rheumatoid
arthritis
Thickened
capsule Bone and
cartilage
Slight synovial
hypertrophy Joint capsule erosion
and synovial
Osteophyte lining
Ulcerated Synovial Increased
synovial fluid
cartilage cavity
Sclerotic bone Cartilage Pannus
formation
Joint space
narrowing
Subchondral
bone cyst
A B C D E

FAS1_2019_11-Musculo.indd 466 11/7/19 5:23 PM