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: Medicine
A 35 - year old male develops involvements of PIP, DIP and metacarpophalangeal joints with sparing of wrist and carpometacarpal joints. The probable diagnosis is: 
Select and explain. 
A. Psoriatic ahopathy, B. Osteo ahritis, C. Rheumatoid ahritis, D. Pseudo gout
A: Psoriatic ahopathy
Answer: A: Psoriatic ahopathy 
Explanation: Answer is A (Psoriatic ahropathy):Psoriatic ahritis involves PIP, DIP and metacarpophalangeal joints, and may or may not involve the wrist.Involvement of DIP makes rheumatoid ahritis unlikely. DIP is spared in rheumatoid ahritis.Involvement of metacarpophalangeal joints makes osteoahritis unlikely. Metacarpophalangeal joints and carpometacarpal joint with the exception of base of thumb are spared in osteoahritis.