This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
Extra - aicular manifestations of RA are all except 
Select and explain. 
A. Rheumatoid nodule, B. Pericarditis, C. Spleen atrophy, D. Osteoporosis
C: Spleen atrophy
Answer: C: Spleen atrophy 
Explanation: Ref - Davidsons 23e p1024