Evaluation - Ankylosing Spondylitis

ESR and C-reactive protein elevated in majority.
Mild anemia.
Rheumatoid factor and ANA negative.
HLA-B27 may be helpful in pts with inflammatory back symptoms but negative x-rays.
Radiographs: early may be normal. Sacroiliac joints: usually symmetric; bony erosions with “pseudowidening” followed by fibrosis and ankylosis. Spine: squaring of vertebrae; syndesmophytes; ossification of annulus fibrosis and anterior longitudinal ligament causing “bamboo spine.” Sites of enthesitis may ossify and be visible on x-ray. MRI is procedure of choice when plain radiographs do not reveal sacroiliac abnormalities and can show early intra-articular inflammation, cartilage changes, and bone marrow edema.