# Vitamin A (Retinol) Deficiency and Excess

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](/content/browse#playlist-2700/index.html) among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.