A young boy presents with dark patches with itching. On rubbing there is appearance of wheal. Diagnosis is -

Ans is 'b' i.e. Urticaria pigmentosa Urticaria pigmentosao Urticaria pigmentosa (also known as "Generalized eruption of cutaneous mastocytosis (childhood type)) is the most common form of cutaneous mastocytosiso Urticaria pigmentosa is most common in children. It can also occur in adultso Urticaria pigmentosa occurs when there are too many mast cells in the skin.o Urticaria pigmentosa is a characterized by patches of darker skin and very bad itching. Hives can develop when these skin areas are rubbed (Darier's sign). It's caused by the release of histamine from the mast cells.o Adults or adolescents are more likely to have uncommon symptoms like diarrhea, tachycardia, nausea or vomiting, fainting, dizziness, headache.