Melanocytes are reduced in number in all of the following Except
Albinism is a defect in the synthesis of melanin. Melanocytes are normally present and distributed Disorders of reduced melanin synthesis: albinism, Chediak-Higashi and Hermansky-Pudlack Reduced melanocytes is seen in vitiligo, piebaldism and Waardenburg syndrome Albinism. Albinism is a group of genetic disorders characterized by reduced or absent melanin pigmentation, with an overall estimated frequency of about 1 per 20000 in most populations (Ref: Harrison 20th edition pg 1234
Albinism
Vitiligo
Piebaldism
Chemical induced hypopigmentation
Autoimmune skin disorders