A 65-yr-old man with H/O back pain since 3 months. ESR is raised. On examination marked stiffness and mild restriction of chest movements is found. On x-ray, syndesmophytes are present in vertebrae. Diagnosis is -

The clinical profile of the given case fits into Ankylosing spondylitis (A.S.) except for the age. A.S. is usually seen in 2nd or 3rd decades of age with a median age of 23. However "in 5% ofpatients, symptoms begin after 40" - Harrison All other features, i.e. raised ESR, marked stiffness, restriction of chest movements & syndesmophytes are seen in A.S.