This is only a sketchy overview of this very complex condition.
More precise and technical information can be gained by using a search engine or reading books on the subject.

Albinism,Leucism,Hypo/and Hyperpigmentation,Hypo/and Hyperchromism are all terms that describe genetic mutations of colour pigments.
The incidence of albinism is known in all living species.

In humans the colour pigment is melanin and mutations within these colour genes leads to various conditions such as partial or complete albinism,leucism and vitiligo.