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| T1 sagittal pre gad || T2 sagittal || T2 axial|
Diagnosis: Ankylosing spondylitis Ankylosing spondylitis is a chronic inflammatory disease which produces eventual fusion of the lumbosacral spine due to marginal syndesmophyte formation and calcification of the annulus fibrosis. The resulting appearance is termed the "bamboo spine". Dural ectasia is another spinal manifestation of ankylosing spondylitis. Other associations include bilateral symmetric sacroiliac sclerosis, upper lobe pulmonary fibrosis, ulcerative colitis, iritis, and aortic insufficiency. It is overwhelmingly seen in young white men who are HLA B27+. The general differential for dural ectasia includes ankylosing spondylitis, neurofibromatosis type I, Marfan syndrome, Ehlers-Danlos syndrome, and achondroplasia. The combination of dural ectasia with severe degenerative changes of the lumbosacral spine with these plain film findings is most compatible with ankylosing spondylitis. The diffusely increased signal involving the disk and vertebral bodies is due to fatty marrow replacement and infiltration into the intervertebral disks.