Vitamin A (Retinol) Deficiency and Excess

Summary

Vitamin A (Retinol) imbalances include syndromes of deficiency and excess.

Vitamin A deficiency has a number of characteristic clinical findings, including night blindness (nyctalopia), bitot spots, dry scaly skin (xerosis cutis), and keratomalacia (corneal liquefaction).

Vitamin A excess is more common than deficiency, and chronic hypervitaminosis A is characterized by dry skin, joint pain, pseudotumor cerebri, and hepatomegaly. Acute vitamin A toxicity presents with nausea/vomiting and vertigo. Crucially, vitamin A is teratogenogenic, and prescription of retinol-containing drugs should be carefully considered in sexually-active and pregnant women.

Key Points

• Vitamin A (Retinol) Deficiency
  • Usually due to fat malabsorption
    • pancreatic insufficiency (e.g. cystic fibrosis), biliary obstruction, or small-bowel resection are potential causes
  • Clinical Presentation (“skin and eyes”)
    • Night blindness (nyctalopia)
    • Corneal degeneration (keratomalacia) = liquefaction of cornea
    • Bitot spots (foamy spots) on conjunctiva
      • formed by squamous metaplasia
    • dry, scaly skin (xerosis cutis)
      • via follicular hyperkeratosis and loss of sebaceous gland function
    • Immunosuppression
      • T-cells need Vitamin A for normal maturation
• Vitamin A (Retinol) Excess
  • Classically in young women taking isotretinoin (vitamin A derivative) for acne
  • Acute hypervitaminosis A (low-yield)
    • nausea, vomiting, vertigo, and blurred vision
  • Chronic hypervitaminosis A
    • Pseudotumor cerebri/idiopathic intracranial hypertension (IIH)
      • headache and papilledema
    • Hepatomegaly/hepatotoxicity
    • Dry skin/skin changes
    • Alopecia, hyperlipidemia, and joint pain (arthralgias) may be seen
  • Teratogenic (high-yield**)
    • ⊝ pregnancy test and two forms of contraception are required before isotretinoin is prescribed
    • Potential effects include craniofacial abnormalities (cleft palate), cardiac abnormalities (transposition of great vessels, tetralogy of fallot),posterior fossa CNS defects, and auditory defects

Find Vitamin A Deficiency and Excess and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.