TY - JOUR T1 - Early Spondyloarthritis in an HLA-B27-positive Monozygotic Twin Pair: A Highly Concordant Onset, Sites of Involvement, and Disease Course JF - The Journal of Rheumatology JO - J Rheumatol SP - 1464 LP - 1466 VL - 35 IS - 7 AU - ULRICH WEBER AU - CHRISTIAN W.A. PFIRRMANN AU - RUDOLF O. KISSLING AU - C. RONALD MACKENZIE AU - MUHAMMAD A. KHAN Y1 - 2008/07/01 UR - http://www.jrheum.org/content/35/7/1464.2.abstract N2 - To the Editor: Susceptibility to ankylosing spondylitis (AS) and the related spondyloarthropathies (SpA) is determined by a strong polygenetic predisposition interacting with as-yet unknown environmental factors. HLA-B27 is one of the major disease susceptibility genes, and studies of HLA-B27-positive twins have shown a concordance rate of 63% among monozygotic versus 24% in dizygotic twin pairs1–5. Making an early diagnosis of AS and related SpA is often challenging, and there are no validated diagnostic criteria6–10. Magnetic resonance imaging (MRI) is the imaging method of choice for early detection and assessment of inflammatory lesions in the axial skeleton prior to… ER -