Inflammatory Arthritis: RA vs. AS
Autoimmune & Seronegative Spondyloarthropathies
1. Comparison Table
| Feature | Rheumatoid Arthritis (RA) | Ankylosing Spondylitis (AS) |
|---|---|---|
| Pattern | Symmetrical, small joints (MCP, PIP, MTP). | Axial skeleton (SI joint, spine). |
| Morning Stiffness | > 60 minutes (improves with activity). | > 30 minutes (improves with exercise). |
| Genetics | HLA-DR4 | HLA-B27 |
2. High-Yield NEET PG Pearls
- RA Deformities: Boutonnière (PIP flexion, DIP hyperextension), Swan-neck (PIP hyperextension, DIP flexion), and Z-thumb.
- AS Radiography: Bamboo spine (syndesmophytes), “Shiny corner” sign (Romanus lesion), and SI joint ankylosis.
- AS Extra-articular: Anterior Uveitis (most common), apical lung fibrosis, and aortic regurgitation.
- Diagnosis: Schober’s test (reduced spinal mobility) is diagnostic for AS. RA is diagnosed using ACR/EULAR criteria (includes RF and Anti-CCP).
3. Note on Resources
For more detailed breakdowns, clinical vignettes, and practice questions covering these complex autoimmune conditions, please visit mymedschool.org.