Albinism is a group of genetic disorders affecting one out of every several thousand humans and other animals. It involves
a deficiency of melanin, the dark brown
pigment responsible for coloration. Eyes, skin and hair, and other body parts may be affected. A totally albino animal has milky-white skin and white hair or feathers. The iris of the eyes is pink, and reflected light in the retina is red, because no color masks the blood vessels. The eyes are light-sensitive and often astigmatic. Occasionally albinism is associated with mental or physical retardation.
Total albinism is rare in wild
animals because few survive to reproductive age. They may lack protective coloration against predators; be driven away by their fellow creatures; or be unable to bear exposure to needed sunlight. Partial albinism is less disabling and is characterized by the appearance of white spots on the skin or white patches in the hair. Vitiligo is the absence of pigment in some body areas only.
Several independent defects can cause albinism: a complete lack of melanocytes, or pigment cells; interference in the migration of the cells to their proper location during embryo development; failure of the cells to produce melanin because of lack of tyrosinase, the stimulating enzyme; or abnormalities within the cells. The gene involved in albinism is recessive and may appear in the offspring of normally pigmented parents who are carriers of the trait. At present, no method for curing albinism is known.