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Detailed information of HYPERVITAMINOSIS A
HYPERVITAMINOSIS A
DEFINITION:
A disorder due to the excessive ingestion of Vitamin A resulting
in acute and chronic forms.
EPIDEMIOLOGY:
- incidence: ?
- age of onset:
- risk factors:
- congenital absence of enzymes needed to convert provitamin
A carotenoids to vitamin A
- excessive ingestion of carotenoid-containing foods
(mashed)
- chronic nephritis
- diabetes mellitus
- hypothyroidism
- liver disease
2. Hypervitaminosis A
- acute or chronic ingestion of vitamin A
PATHOGENESIS:
- food sources of vitamin A (retinol)
- meats - liver, fish-liver oil
- dairy - whole milk, milk fat products, egg yolk, fortified
margarines
- food sources of provitamin A (carotenoids)
- veggies - green and yellow
- fruits - yellow
- intestinal absorption
- while beta-carotenes are partly absorbed by the intestinal
lymphatics, most of the carotenes are absorbed by the
intestinal mucosa after being cleaved into 2 molecules of
retinol -> in the presence of bile, retinol is absorbed by the
intestinal mucosa and esterified with palmitic acid while in
the mucosa -> transported to and stored in the liver ->
hydrolyzed to free retinol when needed and trans-ported to
sites of action:
- eyes as a component of retinal pigments
- bones and teeth for development
- epithelia for differentiation and maturation
2. Pathogenesis
- may occur after the ingestion of 10,000 ug or more of
vitamin A
2. Chronic Hypervitaminosis A
- may occur after the ingestion of excessive doses of
vitamin A for several weeks to months
3. Congential Hypervitaminosis A
- mothers consuming large amounts of Accutane (isotretinoin
[13-cis-retinoic acid]) for treatment of acne during their 1st
trimester, increase the likelihood of teratogenic effects on
the fetus by greater than 20 fold
- effects include:
- brain malformations - microtia
- coronatruncal cardiac defects - thymic defects
CLINICAL FEATURES:
- yellow discolouration of skin (xanthosis cutis) but not
sclera
- dry and cracked skin
2. Acute Hypervitaminosis A
- pseudotumor cerebri
- bulging fontanelle, cranial nerve palsies, diplopia,
drowsiness, papilledema, etc.
2. Gastrointestinal Manifestations
3. Chronic Hypervitaminosis A
- increased intracranial pressure
- irritability
2. Gastrointestinal Manifestations
- anorexia with poor weight gain
- hepatomegaly
- liver cirrhosis
- splenomegaly
3. Musculoskeletal Manifestations
- limitation of motion
- tender swelling of bones
4. Cutaneous Manifestations
- alopecia
- desquamation of the palms and soles
- fissuring of corners of mouth
- pruritus
- seborrheic cutaneous lesions
- xanthosis cutis
INVESTIGATIONS:
- carotinemia (urine does not become dark)
2. Hypervitaminosis
- elevated retinol
- hypercalcemia
- elevated liver function tests (liver cirrhosis)
2. Imaging Studies
- craniotabes (decreased mineralization of the skull)
- hyperostosis of long bones (usually mid shaft)
MANAGEMENT:
- eliminate sources of vitamin A and/or carotenoid
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Pediatric Database - HYPERVITAMINOSIS A
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