This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast, Subject name: Pathology
Which one of the following is not a characteristic feature of rheumatoid ahritis? 
Select and explain. 
A. Sacroilitis, B. Metacarpophalangeal joint involvement, C. Symmetrical ahritis, D. Positive rheumatoid factor
A: Sacroilitis
Answer: A: Sacroilitis 
Explanation: In 80%of Rheumatoid ahritis have serum IgM autoantibodies that bind to fc poion of the IgG. These autoantibodies are called rheumatoid factor. Ahritis and metacarpophalangeal joints involvement is surely present in rheumatoid ahritis. But sacrolitis is not at all related to rheumatoid ahritis. It is a condition in which one or both sacroiliac bones are affected with inflammation. In this condition there is pain in buttock or lower back. Ref:Robbins basic pathology 9th edition page no 784 785,786