This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Papulosquamous Disorders, Subject name: Skin
Least common site involvement in psoriasis is: 
Select and explain. 
A. Scalp involvement, B. Nail involvement, C. CNS involvement, D. Arthritis
C: CNS involvement
Answer: C: CNS involvement 
Explanation: Ans. c. CNS involvementScalp is a common site of involvement in psoriasis. Corona psoriatica is a band of psoriasis, projecting beyond hairline on forehead.Nail changes in psoriasis are pitting, onycholysis, subungual hyperkeratosis, splinter hemorrhages, uneven surface.