According to the WHO, vitamin A deficiency is incipient at levels of 10 to 20 µg/dl and marked at levels below 10 µg/dl. Only when liver stores are depleted do plasma vitamin A levels also decrease, although there is a clear vitamin A deficiency in the tissues even before the plasma concentration is depleted. The first signs of vitamin A deficiency are manifested by visual disturbances and dry, scaly skin. In later stages, loss of appetite, higher susceptibility to infections – especially pneumonia – taste and hearing disorders, reduced fertility and early childhood malformations may occur, and even death. Typical symptoms of vitamin A deficiency include night blindness or xerophthalmia. Respiratory diseases are a common accompaniment of latent vitamin A deficiency. As a cause, changes in the respiratory mucosa play an important role, with a significant loss of ciliary-bearing cells and a definite increase in secreting cells – metaplasia. These pathophysiologic processes cause increased susceptibility to infection and lead to increased morbidity and mortality in children in third-world countries.
Typical changes caused by vitamin A deficiency
General symptoms
- Fatigue
- Loss of appetite
- Increased risk of kidney stone formation
Eye
- Dryness, itching and redness of the conjunctiva.
- Disruption of dark adaptation to hemeralopia – slowed adaptation to twilight vision due to reduction of the light-sensitive pigment rhodopsin in rods.
- Conjunctival or corneal xerosis.
- Bitot spots (white spots on the outside of the conjunctiva due to accumulated keratinized material), keratomalacia, blindness.
Ear
- Hearing disorders (to be discussed)
- Increased vulnerability
Nose
- Decreased sensitivity to odors
Skin, mucous membranes
- Drying up to cornification of mucous membranes, atrophy of salivary glands and larynx.
- Increased gingivitis, stomatitis, bronchitis and pneumonia with further decrease in vitamin A stores.
- Atrophy of the intestinal epithelium with absorption disorders.
- Dry, rough, itchy skin with rashes, dry, brittle nails and hair.
- Increased risk of cancers of the lungs, esophagus, bladder, prostate, cervix, stomach and intestines, and larynx.
Blood
- Hypochromic anemia
Bones, teeth
Central nervous system
- Increase in intracerebral pressure, hydrocephalus in neonates.
Gonads
- Disorders of spermatogenesis
Teratogenicity
- Malformations especially area of the auditory organ in varying degrees.
- Multiple malformations of the gastrointestinal and urogenital tract.
