Rheumatology · HLA-B27 Spondyloarthropathy Cluster: Ankylosing Spondylitis, Psoriatic Arthritis, Reactive Arthritis, IBD-Associated Arthritis

Seronegative Spondyloarthropathies

MS1/MS2 medical students19 questions

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This file owns the HLA-B27 spondyloarthropathy cluster as a clinical reasoning framework: ankylosing spondylitis (axial-predominant), psoriatic arthritis (peripheral with axial overlap and DIP/nail/dactylitis features), reactive arthritis (post-infectious with classic triad), and IBD-associated arthritis (Type 1 oligo paralleling IBD activity vs Type 2 polyarthritis independent of IBD); the unifying anatomic target is the enthesis (introduced in File 1, applied here as the inflammatory site); the unifying cytokine driver is the IL-17/IL-23 axis (introduced in Core Immunology File 5, applied here as the rationale for biologic selection); the seronegative pattern (RF and anti-CCP negative) and the HLA-B27 association are the immunologic markers.

Prerequisites

MSK Anatomy, Histology, Embryology & Joint Biology (the enthesis four-zone architecture — tendon → uncalcified fibrocartilage → tidemark → calcified fibrocartilage → bone — directly applied here as the inflammatory target)Approach to Inflammatory Arthritis & Rheumatoid Arthritis (the four-pillar inflammatory arthritis framework — joint pattern + autoantibody + extra-articular feature + acute-phase reactants — and the DIP-sparing-in-RA discriminator that PsA's DIP involvement breaks)HLA class I biology including HLA-B27 (owned at the table level)IL-17/IL-23 cytokine axis biology, Th17 differentiationBasic ophthalmology (anterior chamber anatomy, uveitis types)Basic gastroenterology (IBD overview)

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Seronegative Spondyloarthropathies

Prerequisites