Albinism

Albinism consists of a group of genetic disorders of the melanin pigmentary system which occurs throughout the animal kingdom from insects, fish and birds right up to human beings. It is characterized by an absence of or decrease in melanin which, in the human varieties of albinism, takes two forms: oculocutaneous albinism and ocular albinism. The former (which is by far the commoner) manifests as a lack of pigmentation in the skin, hair and eyes; in ocular albinism the loss of melanin is limited to the eyes and skin pigmentation is normal. All human albinos have visual problems – there is hypopigmentation of the iris, choroid and retina as well as maldevelopment of the fovea, a part of the retina which mediates central vision. The typical eye signs are photophobia (an abnormal, often painful, sensitivity to sunlight leading to its avoidance), nystagmus (involuntary, rhythmical oscillations of the eyeballs, usually in a horizontal plane), squint and a decreased visual acuity (in severe cases amounting to partial blindness). This chapter will concern itself only with oculocutaneous albinism.

History

Allusions to albinism date from antiquity but the actual term ‘albino’ (from the Latin albus, white) was coined by the seventeenth-century Portuguese explorer, Balthazer Tellez, who sighted certain ‘white’ Negroids on the west coast of Africa. Columbus, however, was claimed to have encountered such people (near Trinidad) at the time of his fourth voyage to America in 1502. The identification of albinos was hardly a feat of recognition: compared with normally pigmented Negroids, these albinos were highly conspicuous, and it was noted that their marked photophobia confined them to their huts until twilight.