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What is A 5 yr old male child has multiple hyperpigmented 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. Most likely diagnosis: and explain in detail?
Gentle rubbing of a lesion causes local itching, erythema, and wheal formation after 2-5 minutes which may be present for 30 min or few hrs. This is the Darier's sign and is seen in uicaria pigmentosa.