Source / episode info
- **Episode:**99
- **Title:**Divine Intervention Episode 99 – USMLE Step 1 Rheumatology Review (Part 1)
- **Published:**2019-05-11
- Source:Episode page
One-liner
This episode provides a comprehensive review of key rheumatologic conditions, including the distinguishing features of dermatomyositis (skin rash + proximal weakness), Sjögren's syndrome (dry eyes/mouth/joints), seronegative spondyloarthropathies (sacroiliitis, enthesitis), and systemic sclerosis (limited vs. diffuse forms).
High-yield summary
- Dermatomyositis: Characterized by proximal muscle weakness and specific skin findings: Gottron's papules (MCP/PIP) and Heliotrope rash (periorbital violaceous erythema). Histology shows perifascicular inflammation, mediated by CD4+ T cells.
- Sjögren's Syndrome: The classic triad is dry eyes (keratoconjunctivitis sicca), dry mouth (xerostomia), and joint pain/arthritis. Associated antibodies include anti-SSA (Ro) and anti-SSB (La). High risk of developing lymphoma and renal tuberculosis.
- Ankylosing Spondylitis (AS): A seronegative spondyloarthropathy characterized by sacroiliitis, enthesitis, and spinal fusion leading to a "bamboo spine." It is strongly associated with HLA-B27 positivity.
- Systemic Sclerosis (Scleroderma): Limited systemic sclerosis (CREST syndrome) involves the hands/forearms/face and is linked to anti-centromere antibodies. Diffuse systemic sclerosis involves visceral organs (lungs, kidneys) and is linked to anti-Scl-70 antibodies.
- Inflammatory Arthritis: Joint fluid WBC counts are key: Septic arthritis >50,000 cells; Inflammatory <30,000 cells (often 10–30k with lymphocytes).
Learning objectives
- Differentiate between dermatomyositis and polymyositis based on clinical presentation and autoantibodies.
- Recognize the classic triad and associated antibodies of Sjögren's syndrome.
- Identify the key features, seronegative status, and complications of Ankylosing Spondylitis.
- Distinguish between limited (CREST) and diffuse systemic sclerosis using antibody profiles and organ involvement patterns.
- Apply knowledge of joint fluid analysis to differentiate septic from inflammatory arthritis.
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