Night Blindness


↓ Ca2+ ↑ P = hypothyroidism??????

Deficiency of fat-soluble vitamins (A, D, E, K) is often due to malabsorption (e.g., cystic fibrosis, cirrhosis, celiac disease [sprue], pancreatic insufficiency). Parenteral supplementation may be necessary if high-dose oral supplements fail to correct the problem.

 

 

 

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Vitamin Aa,b,c 60 mg PO, repeated 1 and 14 days later if ocular changes; 30 mg for ages 6–11 months
15 mg PO qd × 1 month if chronic malabsorption

 

aAssociated with fat malabsorption.

bAssociated with chronic alcoholism; always replete thiamine before carbohydrates in alcoholics to avoid precipitation of acute thiamine deficiency.

cAssociated with protein-calorie malnutrition.

dTherapy must be monitored by serum calcium measurements.

 

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Vitamin A deficiency is associated with an increased risk of which of the following:

The answer is E. Vitamin A, also known as retinol, is a fat-soluble vitamin that has biologically active metabolites retinaldehyde and retinoic acid that are all important for good health. Collectively, these molecules are known as retinoids and are important for normal vision, cell growth and differentiation, and immunity. Vitamin A is found in its preformed state in liver, fish, and eggs, and it is often consumed as carotenoids from dark green and deeply colored fruits and vegetables. In developing countries, chronic vitamin A deficiency is endemic in many areas and is the most common cause of preventable blindness. In milder stages, vitamin A deficiency causes night blindness and conjunctival xerosis. This can progress to keratomalacia and blindness. Given the broad biologic functions of vitamin A, however, deficiency at any stage increases the risk of mortality from diarrhea, dysentery, measles, malaria, and respiratory disease. Vitamin A supplementation has been demonstrated to decrease childhood mortality by 23%–34%. About 10% of pregnant women in undernourished settings develop night blindness in the later trimesters of pregnancy, and vitamin A deficiency in pregnancy is associated with an increased risk of maternal infection and death.

 

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Children with severe vitamin A deficiency develop accumulation of a glycosaminoglycan on the corneal epithelium and is accompanied by “dry eye.” Which of the following types of glycosaminoglycan would you expect to find accumulated on the surface of the cornea?

Answer

 

 

 

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