This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'A 5 year old male child has multiple hyper pigmented macules over the trunk, on rubbing the lesion with the rounded end of a pen. He developed urticarial wheal, confined to the border of the lesion. The most likely diagnosis is \nSelect and explain. \nA. Fixed drug eruption, B. Licken planus, C. Urticaria pigmentosa, D. Urticarial vasculitis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Urticaria is characterized by large, irregularly shaped pruritic, erythematous wheels\n\nSpecial forms of urticaria have special features (Dermographism, cholinergic urticaria, solar urticaria, or cold uritcaria)\nMost incidents are acute and self-limited over a period of 1-2 weeks\nChronic urticaria (episodes lasting> 6 weeks) may have an autoimmune basis\nThe most common immunologic mechanism is hypersensitivity mediated by IgE, seen for most patients with acute urticaria\nThe morphology of the lesions may vary over a period of minutes to hours, resulting in geographic or bizarre, pattern, true urticaria last less than 24 hours and often only 2-4 hours.\nThe most common cause of acute urticaria are foods, viral infections and medications Diagnosis - In vivo allergy skin testing and in vitro RAST testing\nDetermination of serum tryptase (Increased in anaphylaxis, systemic mastocytosis, non IgE mediated disease ("anaphylactoid reaction")\nACE inhibitors and Angiotensin II receptors antagonist therapy is contraindicated.\n\nUrticaria pigmentosa (mastocytosis) - consists of multiple irregularly shaped hyperpigmented macule which may present on the trunk and extremities.\n\nStroking the skin through the lesion with a blunt instrument elicits the classical "triple response of Lewis" called Darier\'s sign\n\nTreatment - Avoides taking drugs of Aspirin, NSAID\', drugs, morphine, codeine, procaine, thiamine, polymyxin B and alcohol.\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0 .\n\nThe main stay of treatment is initially includes HI antihistamines (Hydroxyzine, cyproheptadine, Loratadine\nDoxepin (TCA) - very effective in chronic urticaria.\n\nUrticarial vasculitis may be seen as part of serum sickness, associated with fever and arthralgia.', 'role': 'assistant'}]