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
"Telescope fingers" occur in 
Select and explain. 
A. Rheumatic ahritis, B. Rheumatoid ahritis, C. Psoriatic ahritis, D. Reiter's ahritis
C: Psoriatic ahritis
Answer: C: Psoriatic ahritis 
Explanation: Ahritis mutilans (A feature of psoriatic ahritis) This is a deforming erosive ahritis targeting the fingers and toes; it occurs in 5% of cases of PsA. Prominent cailage and bone destruction results in marked instability. The encasing skin appears invaginated and 'telescoped' ('main en lorgnette') and the finger can be pulled back to its original length. Ref Davidsons 23e p1033