What classic symptom suggests ankylosing spondylitis?

Ankylosing spondylitis is a type of inflammatory arthritis primarily affecting the spine, leading to progressive stiffness and pain in the back. One of the hallmark symptoms of ankylosing spondylitis is back stiffness that improves with movement. This pattern is typical because, during periods of inactivity, particularly in the morning, individuals often experience increased stiffness and discomfort. However, engaging in physical activities tends to relieve this stiffness, a feature that distinguishes ankylosing spondylitis from other forms of back pain, which typically worsen with movement.

The other symptoms listed, while they may relate to various conditions, do not specifically point to ankylosing spondylitis. Joint swelling in the hands can occur in different types of arthritis but is not characteristic of this condition; weight loss and fever might suggest systemic illness or infection rather than a musculoskeletal issue; chest pain upon inhalation is often related to respiratory conditions or pleuritic sources rather than to ankylosing spondylitis. Thus, back stiffness that improves with movement is the most classic and relevant symptom of ankylosing spondylitis.