A 13-year-old boy with patchy depigmented skin on the right flank and upper thigh in segmental distribution. The depigmentation started 1 year back but has been static for last 4 months. Mother reports use of topical steroids which was ineffective.

Ans. (b) Segmental vitiligo.* Vitiligo is an acquired autoimmune condition targeting melanocytes and present with localized or widespread white depigmented patches. Thyroid autoimmune dysfunction is associated.* Piebaldism is an autosomal dominant condition characterized by white forelock and circumscribed depigmented patches affecting the body. It is caused by a defect in proliferation and migration of melanocytes during embryo- genesis. Unlike vitiligo, it is congenital and non-progressive. In the question the depigmentation started at age of 12 years and patient presented at 13 years.* Nevoid hypomelanosis is characterized by hypopigmented patches or streaks which follow the lines of Blaschko. They are present at birth and may develop in the first 2 years of life.