Decrease number of melanocyte is seen in:
Piebaldism is a Autosomal dominant disease characterized by patches of skin that lack melanin as a result of defect in migration of melanoblast from neural crest to skin.
Skin biopsy: Hypo melanotic area-few to no melanocytes. Vitiligo: is an acquired disease and similar patch of loss ofmelanin, but the loss develops after birth and progressive. Albinism: Congenital inability to synthesize melanin.
Albinism
Piebaldism
Ichthyosis
Chemical leucoderma