An HLAB27 gene disorder that is common in families and typically affects the spine –cervical, thoracic, lumbar regions – and sacroiliac joints in young to middle age men and women causing early am stiffness and pain which improves as the day progresses (as opposed to osteoarthritis or mechanical back pain which worsens as the day progresses). Diagnosis can be delayed and difficult unless there is high suspicion as this arthritis is a seronegative arthritis, meaning that tests for rheumatoid arthritis and connective tissue diseases are negative. Even inflammatory markers may be normal, so a good history and physical exam are paramount.