This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: S.T.D., Subject name: Skin
Groove sign is seen in? 
Select and explain. 
A. Chancroid, B. Syphilis, C. LGV, D. Psoriasis
C: LGV
Answer: C: LGV 
Explanation: Ans. (c) LGVRef: Rook's 8/e, p 34.33, Greenberg's Text-Atlas of emergency medicine by Michael I. Greenberg p. 367, Nord guide to rare diseases, p 8