Extended erosion (T1SE sequence). HLA B27 positive, 28-year-old male AS patient with inflammatory back pain for five years. The right ilium shows erosion which extends across the entire joint surface (arrows). HLA-B27, human leucocyte antigen B27; T1SE, T1-weighted spin echo sequence.
Weber et al. Arthritis Research & Therapy 2012 14:R124 doi:10.1186/ar3854