Answer:
Low back pain
18-year-old men
Step-by-step explanation:
This is a form of athritis which affect the spine and other joints of the body. A percentage of individuals with this disease begin to experience symptoms at the age of 18 years(early adulthood) which is the period when it predominantly starts.
The disease is also characterized by the presence of back pain as a result of the spine found at the back being affected in this case.