Definition of Hypervitaminosis A:

Hypervitaminosis means you having too much of a certain vitamin stored in your body. People with hypervitaminosis A have too much vitamin A.

Causes, incidence, and risk factors:

There are two types of vitamin A hypervitaminosis:

• Acute -- caused by taking too much vitamin A over a short period of time
• Chronic -- happens when too much of the vitamin is present over a longer period

In an infant, the sudden intake of too much vitamin A may cause a bulging fontanelle ("soft spot" on the head), and symptoms resembling those of a brain tumor. This group of symptoms is called pseudotumor cerebri and includes a bulging fontanelle, papilledema (swelling of the optic disc), and double vision. Vomiting and drowsiness are common.

The symptoms in adults are less specific. Headache, visual changes, and impaired consciousness suggestive of pseudotumor cerebri may occur. Other symptoms may include nausea, vomiting, dizziness, and blurry vision.

Chronic vitamin A toxicity develops after taking too much vitamin A for long periods. Bone pain and swelling of the bones is common, often associated with high levels of calcium in the blood. Other symptoms include hair loss, high cholesterol, liver damage, and vision problems. Symptoms are often subtle and may include fatigue, malaise, and nausea.

In children, hypervitaminosis A can cause craniotabes (abnormal softening of the skull bones). Irritability, decreased appetite, itchy skin, and poor weight gain are common. There may be skin changes with seborrhea (extremely oily skin and hair), and cracking at the corners of the mouth.

Increased intracranial pressure is seen in both acute and chronic forms.