Failure of enzymic cleavage of beta-carotene. The cause of vitamin A deficiency in a child.

Abstract

A 10-year-old Lebanese Arab girl had vitamin A deficiency as evidenced by night blindness, bilateral Bitot's spots, and very low plasma vitamin A concentration (7μg/100 ml). Total plasma carotenoid values were high with about 50% as β-carotene. Repeated blood sampling after large doses of β-carotene failed to produce any retinyl ester in the plasma whereas there was significant rise of ester levels in three control subjects. Preformed vitamin A cured the clinical condition and caused retinyl ester to appear in the plasma. There was no malabsorption, hypothyroidism, or liver dysfunction. The evidence suggests failure of enzymic conversion of β-carotene to retinal in the intestine as the cause of vitamin A deficiency.