Vitamin A toxicity

What is vitamin A toxicity?

Vitamin A is a fat soluble retinoid. It also called retinol. Vitamin A is needed for immunity, visual and dermatological health as well as cell communication and growth. In excessive amounts, however, it can accumulate in the liver and cause a wide array of symptoms. Toxicity is classified as either acute or chronic.

Vitamin A toxicity is also known as hypervitaminosis A.

What causes vitamin A toxicity?

Acute toxicity

The most common cause of acute vitamin A toxicity is the ingestion (generally accidental) of over 300,000 IU of vitamin A.

Chronic toxicity

The most common cause of chronic vitamin A toxicity is the regular ingestion of over 100,000 IU daily, which is sometimes prescribed for dermatological conditions such as acne.

What are the signs and symptoms of vitamin A toxicity?

Signs and symptoms of acute vitamin A toxicity can include:

• Gastrointestinal: nausea, vomiting, loss of appetite, abdominal pain
• Neurological: dizziness, irritability, drowsiness, increased intercranial pressure due to cerebral oedema, and headache
• Dermatological: rash or desquamation (peeling skin)
• Coma and death

Signs and symptoms of chronic vitamin A toxicity can include:

• Gastrointestinal symptoms: hepatomegaly, splenomegaly
• Neurological symptoms: severe headache, pseudotumour cerebri
• Dermatological symptoms: rash, thin and coarse hair, alopecia of the eyebrows, itch, skin that is dry, rough or cracking, and dry or cracked lips
• Musculoskeletal: weakness, cortical hyperostosis of the bone, arthralgia, easy fractures

In children, signs and symptoms of vitamin A toxicity are:

• Neurological: irritability, drowsiness, delirium, coma, increased intercranial pressure, bulging fontanelles (in infants), psychiatric changes, cerebral oedema
• Ophthamological: bulging eyeballs, swelling of the cortical disc, visual disturbances
• Dermatological: skin discoloration and/or desquamation, itch

It is also important to note that vitamin A is highly teratogenic if taken during pregnancy (especially in the first 8 weeks) if intake exceeds 10,000 IU daily. Birth defects can also be caused by isotretinoin or other oral retinoids, if taken while pregnant.

Vitamin A and teratogenicity

Excessive intake of Vitamin A during pregnancy has been associated with the following birth defects, collectively known as retinoic acid syndrome:

• Encephalitis
• Microcephaly
• Craniofacial malformations (most commonly a cleft palate)
• Cardiovascular malformations (most commonly a transposition of the great vessels)
• Thymus malformation/dysfunction

How is vitamin A toxicity diagnosed?

Diagnosis of vitamin A toxicity is based on signs and symptoms, patient history, lifestyle habits and use of supplements. There is sometimes a poor correspondence between toxicity and serum retinol levels. However, serum levels can sometimes be between 1,000 and 20,000 (with a normal range being 200 to 800 µg/L). The blood sample must be protected from light.

How is vitamin A toxicity treated?

Vitamin a toxicity is treated by stopping the use of vitamin A supplements. Generally, signs and symptoms will resolve on their own with 1–4 weeks, depending on their severity. Birth defects caused by vitamin A toxicity during pregnancy are irreversible.