Vitamin A deficiency Domina Petric, MD

Introduction Hepatic stores are great enough to provide retinol. The plasma retinol level is only minimally affected by vitamin A deprivation. Cellular functions of vitamin A can be expected to change only after transport of the vitamin is reduced, after vitamin A stores have dropped to such levels as to reduce plasma retinol–RBP concentrations. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Adequate vitamin A status Hepatic retinyl ester stores >20 µg (>0.07 µmol) RE per gram indicate adequate vitamin A status. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Vitamin A deficiency Primary vitamin A deficiency: lack of both provitamins A and preformed vitamin A in diets. Secondary vitamin A deficiency: failures in provitamins A and preformed vitamin A in their physiologic utilization. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Primary vitamin A deficiency Primary vitamin A deficiency can occur among children and adults who consume diets composed of few servings of yellow and green vegetables and fruits and liver. For infants and young children, early weaning can increase the risk of primary deficiency. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Secondary vitamin A deficiency Chronically impaired enteric absorption of lipids, such as in diseases affecting the exocrine pancreas: pancreatitis, cystic fibrosis, nutritional selenium deficiency. Impaired bile production and release: biliary atresia. Consumption of diets containing very low amounts of fat. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Secondary vitamin A deficiency Chronic exposure to oxidants can also induce vitamin A depletion: benzo(α)pyrene in cigarette smoke. Nutritional deficiencies of zinc can also impair the absorption, transport, and metabolism of vitamin A. Zinc is essential for the hepatic synthesis of RBP and the oxidation of retinol to retinal, which is catalyzed by a zinc-dependent retinol dehydrogenase. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Secondary vitamin A deficiency Malnourished populations, which typically have low intakes of several essential nutrients including vitamin A and zinc, are at risk to vitamin A deficiency. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Detecting vitamin A deficiency Vitamin A deficiency can be detected by clinical diagnosis or by assessment of biochemical or histological indicators. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Clinical signs Clinical signs include impaired dark adaptation, nyctalopia and ocular lesions. Nyctalopia is the first functional sign of vitamin A deficiency that can be measured. The condition can be detected by using the papillary response to a graduated light stimulus. Examination by slit lamp can reveal fundus specs and disrupted rod outer segments with the possible involvement of similarly disrupted cones. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Clinical signs conjunctival xerosis with or without Bitot’s spots Ocular lesions can be diagnosed by direct examination of the eye: conjunctival xerosis with or without Bitot’s spots corneal xerosis ulceration keratomalacia corneal scars September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Bitot´s spot Flickr.com September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Bitot´s spot Almost always bilateral oval or triangular structures first appearing temporal to the limbus and comprising a thickened, superficial layer of flattened cells usually with a keratinizing surface, a prominent granular cell layer, and acanthotic thickening with a disorganized basal cell layer, but with no goblet cells. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Conjunctival impression cytology Morphological changes in epithelial cells blotted from the conjunctival surface can be detected by histologic examination. The presence of enlarged, flattened epithelial cells and few or no goblet cells is indicative of vitamin A deficiency. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Progression of vitamin A deficiency With progressing vitamin A deficiency, the conjunctival surface takes on a dry, corrugated, irregular surface, ultimately developing an overlay of white, foamy, or “cheesy” material consisting of desquamated keratin and a heavy bacterial growth. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

First sign These lesions can be seen using the slit lamp microsope. Fine, fluorescein-positive, superficial punctuate keratopathy that usually begins in the inferior aspect of the cornea, particularly inferonasally. These lesions can be seen using the slit lamp microsope. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Superficial punctate keratopathy Myalcon.com September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Progression The lesions become more numerous and concentrated, involving larger portions of the corneal surface. By the time most of the corneal surface is involved, the lesions are generally apparent by hand–light examination as a haziness and diminished wettability on the corneal surface: corneal xerosis. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Corneal xerosis Flickr.com September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Sometimes the ulcer is deep enough to effect stromal loss. Progression Corneas affected at this level of corneal xerosis also show stromal edema, mostly in the inferior aspect. If untreated, the condition progresses to the point of corneal ulceration, frequently characterized by the presence of a single (or sometimes two to three) sharply defined ulcer varying in depth, usually one-fourth to one-half of corneal thickness. Sometimes the ulcer is deep enough to effect stromal loss. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Corneal ulcer Smartypans.com September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Progression Stromal loss can lead to deep stromal necrosis characterized by gray-yellow, edematous and cystic lesions of varying size from 2 mm to most of the cornea. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Stages of xerophtalmia Keratomalacia 2 Secondary infection Keratomalacia 2 Ultimate involvement of iris/lens Keratomalacia 2 Softening of cornea 1 Xerosis Ultimate extension to cornea 1 Xerosis Dryness of conjunctiva Bitot’s spots September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Laboratory tests The vitamers A can be accurately quantified in biological specimens using high-performance liquid–liquid partition chromatography (HPLC). Serum retinol is a convenient parameter of vitamin A status. RBP and retinol concentrations less than 0.70 µM (20 µg/dl) are considered indicative of vitamin A deficiency. Almost 20% of night blind children have serum retinol above this level. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency General Loss of apetite Retarded growth Drying and keratinization of membranes Infection Death September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Dermatologic Rough scaly skin and hair Healthh.com September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Muscular Muscular weakness September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Skeletal Periosteal overgrowth Restriction of cranial cavity and spinal cord Narrowed foramina September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Vital organs Nephritis September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Nervous system Increased cerebrospinal fluid pressure Ataxia Constricted optic nerve at foramina September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Reproductive Aspermatogenesis Vaginal cornification Fetal death and resorption September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

All signs of vitamin A deficiency Ocular Nyctalopia Xerophthalmia Keratomalacia Constriction of optic nerve September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Treatment Because vitamin A is stored in appreciable amounts in the liver, it can be administered in relatively large, infrequent doses with efficacy. In cases of clear or suspected xerophthalmia, particularly in communities in which the deficiency is prevalent, vitamin A is administered orally in large doses, followed by an additional dose the next day and a third a few weeks later. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Treatment Oral administration of water miscible or oil solutions of the vitamin are as effective as water-miscible preparations administered parenterally. Water-miscible preparations are much more effective than oil solutions when administered parentally (intramuscular injection). Topical administration on the skin is ineffective. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Literature Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. September 16, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.