Vitamin A is a fat-soluble vitamin that plays an important role in vision, immunity, and epithelial proliferation and keratinization.

Vitamin A deficiency is more common in developing countries, where widespread starvation and malnourishment persist. Although rare, it does occur in developed countries, typically as a result of an extremely calorie-restricted diet, as in eating disorders; malabsorption due to medical conditions such as Crohn disease, pancreatic insufficiency, or cirrhosis; or surgical interventions such as gastric bypass surgery or colectomy. Chronic giardiasis may also give rise to malabsorption and subsequent (or resultant) vitamin A deficiency.

Phrynoderma, which presents as hyperkeratotic follicular papules, primarily on the extensor surfaces of the extremities, is caused by vitamin A deficiency. It has also been associated with deficiencies in vitamins B complex (see B1, B2, B6, B7, B12), C, or E and essential fatty acid deficiency. The consensus in the literature is that general malnutrition is most closely associated with its development, rather than isolated vitamin A or other isolated vitamin deficiencies.

Other manifestations associated with vitamin A deficiency include blepharitis, night blindness, diarrhea, muscle weakness, and neuritis. Severe deficiency in vitamin A can lead to destructive eye problems, including xerosis conjunctiva, Bitot spots, corneal xerosis, and keratomalacia.