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: Dental
[{'content': 'A 13-year-old boy with patchy depigmented skin on the right flank and upper thigh in segmental distribution. The\ndepigmentation started 1 year back but has been static for last 4 months. Mother reports use of topical steroids which was\nineffective. \nSelect and explain. \nA. Segmental vitiligo, B. Piebaldism, C. Hypomelanosis of Ito, D. Hypopigmented streaks', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Segmental vitiligo.\n\nVitiligo is an acquired autoimmune condition targeting melanocytes and present with localized or widespread white depigmented patches.\xa0Thyroid autoimmune dysfunction is associated.\nPiebaldism is an autosomal dominant condition characterized by white forelock and circumscribed depigmented patches affecting the body.\xa0It is caused by a defect in proliferation and migration of melanocytes during embryo- genesis. Unlike vitiligo, it is congenital and non-progressive.\nIn the question the depigmentation started at age of 12 years and patient presented at 13 years.\nNevoid hypomelanosis is characterized by hypopigmented patches or streaks which follow the lines of Blaschko.\xa0They are present at birth and may develop in the first 2 years of life.', 'role': 'assistant'}]