Describe vitamin A deficiency and its prevention.

Vitamin a Deficiency

• Its functions — the visual cycle, through rhodopsin in the rods; maintenance of epithelial integrity; immune function; and growth and reproduction
• Sources — preformed retinol from animal foods: liver, egg yolk, milk, butter, ghee, fish liver oil; and provitamin carotenoids, chiefly beta-carotene, from plant foods: green leafy vegetables, carrot, pumpkin, mango, papaya and yellow-orange fruits
• Beta-carotene is converted in the intestinal mucosa, but inefficiently, so plant sources supply far less usable vitamin A than their carotene content suggests; and absorption requires dietary fat, which is why adding a little oil to green leafy vegetables genuinely improves the nutrition
• The ocular signs follow the WHO classification, and knowing the order matters:
• XN — night blindness, the earliest symptom, which is reversible within days of treatment
• The history is easily obtained by asking the mother whether the child stumbles or cannot find things at dusk, and most Indian languages have a local term for it, which should be used when asking
• X1A — conjunctival xerosis; X1B — BITOT spots, which are triangular, foamy, silvery-grey plaques on the temporal conjunctiva
• X2 — corneal xerosis
• X3A — corneal ulceration or keratomalacia involving less than one third of the cornea; and X3B — involving one third or more
• XS — corneal scar; and XF — xerophthalmic fundus
• The critical clinical point is that the transition from X2 to X3 can occur within days, so corneal xerosis is an ophthalmic emergency requiring immediate high-dose vitamin A
• Once keratomalacia has occurred the blindness is permanent, and the affected child has a high mortality, frequently dying of the underlying malnutrition and infection within months
• Measles is the classical precipitant, since it depletes vitamin A stores acutely and damages the corneal epithelium, which is why vitamin A is given to every child with measles
• The risk factors — age 6 months to 5 years; weaning without vitamin A rich foods; protein energy malnutrition, since retinol-binding protein is deficient; measles, diarrhoea and respiratory infection; lack of breastfeeding; and fat malabsorption
• Prophylaxis under the Indian programme — 100,000 IU at 9 months with the measles-rubella vaccine, then 200,000 IU every six months up to 5 years, giving nine doses in all
• Treatment of xerophthalmia — 200,000 IU on day 1, day 2 and day 14 (with age-reduced doses under 12 months), which is the three-dose regimen to memorise
• Vitamin A is also given with measles and in severe malnutrition
• A caution — high-dose vitamin A is teratogenic and must not be given to women who may be pregnant; and excess causes raised intracranial pressure with bulging fontanelle in infants, which is transient
• The long-term solution is dietary — promotion of green leafy vegetables, yellow fruits and vegetables, and home and kitchen gardens; breastfeeding; fortification of edible oil and milk; immunisation, particularly against measles; and control of diarrhoea and worm infestation
• Supplementation is a holding measure, not a solution — it must continue indefinitely, whereas dietary change ends the problem
• Vitamin A saves more lives than eyes, raising survival long before any ocular sign appears
• Corneal xerosis is an ophthalmic emergency, since it can progress to permanent blindness within days
• Treat on day one, day two and day fourteen, which is the three-dose regimen to memorise
• Ask about night blindness using the local term, since most Indian languages have one and mothers recognise it
• Give vitamin A to every child with measles, which acutely depletes stores and damages the corneal epithelium
• Add oil to green leafy vegetables, since carotene absorption requires dietary fat
• Carotene converts inefficiently, so plant sources supply far less usable vitamin A than their content suggests
• Bitot spots are foamy and temporal, and are the classical sign examiners ask to be described
• High-dose vitamin A is teratogenic and must not be given to women who may be pregnant
• Nine doses in all up to five years, beginning at nine months with the measles-rubella vaccine
• Keratomalacia carries high mortality, the child frequently dying of the underlying malnutrition within months
• Supplementation is a holding measure; only dietary change ends the problem permanently