45-year-old man complains of back pain and multiple joints pain. X-Ray shows bilateral sacroilitis. Diagnosis could be: March 2005

Ans. B: Ankylosing spondylitis Ankylosing Spondylitis (AS) is a chronic systemic inflammatory rheumatic disease, primarily affecting the axial skeleton of which sacroilitis is the hallmark. The disease pathogenesis is immune mediated as evident by raised IgA and close relationship with HLA B27. Immunologically there is interaction between class I HLA molecule B27 and T lymphocytes. Tumor necrosis factor has been identified as key regulatory cytokine.The age of onset is second or third decade of life and males are affected two to three times more than females. The risk factors for the disease are presence of HLA B27, male sex, positive family history, etc. Of them HLA B27 is most impoant as there is almost sixteen times increased chance of developing the disease amongst HLA B27 positive relatives. HLA B27 is present in almost 90%-95% cases. The clinical features are insidious onset, dull pain felt in lower lumber region, associated with morning stiffness lasting for few hours, there may be asymmetric ahritis of other joints mainly of lower limbs. Neck pain and stiffness is present in advanced cases. Physical findings include loss of spinal flexion, extension, lumber lordosis, diminished chest expansion, and exaggerated thoracic kyphosis.