This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
All of the following are true regarding ankylosing spondylitis except: March 2010 
Select and explain. 
A. Involvement of sacroiliac joint, B. Most of people are HLAB27 positive, C. 50% of patients may have urinary infection, D. Bamboo spine may be a radiological feature
C: 50% of patients may have urinary infection
Answer: C: 50% of patients may have urinary infection 
Explanation: Ans. C: 50% of patients may have urinary infection