Vitamin A Deficiency Disorders

Vitamin A is essential for maintaining normal retinal function and differentiation of rapidly dividing, bipotential cells. These regulatory roles give rise to specific manifestations of hypovitaminosis A, such as poor photoreceptor function leading to night blindness, metaplasia, and keratinization of mucosal epithelial surfaces leading to clinical abnormalities of conjunctival and corneal xerosis as well as epidermoid metaplasia and other epithelial defects throughout the respiratory, genitourinary, and gastrointestinal tracts and glandular ducts. Deficiency can also impair development or functioning of multiple arms of the immune system that can weaken host defenses against infection. Collectively, all pathophysiological consequences attributed in varying degrees to VA depletion are termed 'vitamin A deficiency disorders (VADD) (Figure 1).

Keratomalacia/ Corneal Ulceration (X3)

Night Blindness (XN)

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