This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Dermatitis, Subject name: Dental
A 5 year old male child has multiple hyperprigmented macules over the trunk. On rubbing the lesion with the rounded end of a pen, he developed uicarial wheal, confined to the border of the lesion. The most likely diagnosis is 
Select and explain. 
A. Fixed drug eruption, B. Lichen planes, C. Uicaria pigmentosa, D. Uicarial vasculitis
C: Uicaria pigmentosa
Answer: C: Uicaria pigmentosa 
Explanation: Darriers sign : uicarial wheal produced in a lesion after it is firmly rubbed with a finger or rounded end of a pen, the wheal is strictly confined to the borders of the lesion. Seen in uicarial pigmentosa, and rarely with cutaneous lymphoma or histiocytosiS FITZPATRICK TEXTBOOK OF DERMATOLOGY , PAGE 12.