Vitamin A deficiency

Vitamin deficiencies

Vitamin A deficiency

Definition

Deficiency of vitamin A, a fat-soluble vitamin, is a major cause of blindness in many areas of the world.

Aetiology

Insufficient intake of carotenoids, especially β -carotene found in carrots and dark green leafy vegetables and retinol found in fish oils, liver, eggs butter and cheese. Dietary vitamin A deficiency is generally seen in the developing world. Occasionally it can be seen in disorders of fat malabsorption, such as cystic fibrosis, cholestatic liver disease and inflammatory bowel disease.

Pathophysiology

Vitamin A is required for maintenance of mucosal surfaces, the formation of epithelium and production of mucus. It also plays a role in normal immune function. Retinal function is dependent on retinol, a constituent of the retinal pigment rhodopsin.

Clinical features

Xerophthalmia begins with night blindness and conjunctival xerosis. Bitot’s spots, which are flecks caused by heaped up desquamated cells occur and progress to corneal xerosis, and eventually corneal clouding ulceration and scaring. Patients are at risk of secondary infection.

Management

Prevention of eye disease with adequate diet and supplementation in patients with disorders of fat metabolism. In pregnant women, vitamin A but notβ carotene is teratogenic.

Xerophthalmia should be treated with oral or intra-muscular retinol. Corneal transplant may be required for irreversible corneal ulceration.

Prognosis

Night blindness is easily reversible. Signs of a dry conjunctiva and Bitot’s spots precede irreversible corneal ulceration unless rapidly treated.