The classic manifestations of a deficiency of vitamin A in man, xerophthalmia and keratomalacia, have until recently been recognized as the only external lesions of this nutritional disorder. The failure of nutrition underlying such conditions is due either to an inadequate amount of the vitamin in the diet or to disease or functional derangements interfering with the utilization of this substance by the body. The relationship of the ocular changes to a deficiency of vitamin A has been established by frequent clinical and experimental observations in man and in laboratory animals.
The specific effect of a diet inadequate only in vitamin A is a keratinizing metaplasia of epithelium in many regions of the body, which is thought to be a phenomenon of repair stimulated by atrophy of the original epithelium. The replacement of normal epithelium by stratified keratinizing epithelium, similar to that of the normal epidermis, produces extensive visceral
FRAZIER CN, HU C. NATURE AND DISTRIBUTION ACCORDING TO AGE OF CUTANEOUS MANIFESTATIONS OF VITAMIN A DEFICIENCYA STUDY OF TWO HUNDRED AND SEVEN CASES. Arch Derm Syphilol. 1936;33(5):825–852. doi:10.1001/archderm.1936.01470110045005
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