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:

Patient is showing features of uicaria pigmentosa. It is a condition caused by an increase in the number of dermal mast cells. Children presents with brownish dermal papules and plaques distributed over the body. On rubbing, these plaques become uicated (Darier's sign). Symptoms are due to the release of histamines. Ref: Color Handbook of Dermatology By R. Rycrof, Pages 33, 34; Field guide to clinical dermatology By David H. Frankel, 2nd Edition, Page 59 3. A Practical Guide to Pediatric Emergency Medicine: Caring for Children By N. Ewen Amieva-Wang, Page 135