Which of the following is a typical sign of ankylosing spondylitis?

• A. Insidious onset
• B. Acute onset
• C. Pain worsens with activity
• D. No night pain

Answer: (A)

Ankylosing spondylitis typically presents with inflammatory back pain that develops gradually in a young adult. The insidious onset reflects a slow, ongoing inflammatory process rather than a sudden event, which helps distinguish it from mechanical causes that start abruptly. Inflammatory back pain often features morning stiffness and improves with exercise or NSAIDs, and it can include night pain that wakes the patient. A sudden onset, pain that worsens with activity, or no night pain do not fit this inflammatory pattern, making gradual onset the best fit.