Vitamin A Deficiency (VAD)
1. Introduction
- Vitamin A (Retinol) is a fat-soluble vitamin essential for vision, immune function, growth, and epithelial integrity.
- Deficiency is a major cause of preventable blindness in children and increases the risk of morbidity and mortality from infections.
2. Etiology (Causes)
- Dietary deficiency: Inadequate intake of vitamin A-rich foods (common in developing countries).
- Malabsorption syndromes: Celiac disease, cystic fibrosis, chronic diarrhea.
- Liver disorders: Impaired storage and metabolism of vitamin A (e.g., cirrhosis).
- Increased requirement: During infections like measles, pregnancy, and lactation.
- Fat malabsorption: Due to bile duct obstruction or pancreatic insufficiency.
3. Pathophysiology
- Vitamin A is vital for:
- Formation of rhodopsin in retinal rods for low-light vision.
- Maintenance of epithelial tissues (skin, mucosa).
- Regulation of gene expression.
- Deficiency leads to impaired vision, keratinization of epithelial tissues, and compromised immunity.
4. Clinical Features
A. Ocular Manifestations (Xerophthalmia) - WHO Classification:
- Night blindness (Nyctalopia): Earliest symptom; impaired adaptation to darkness.
- Conjunctival xerosis (X1A): Dry conjunctiva due to loss of goblet cells.
- Bitot’s spots (X1B): Foamy, white patches on the conjunctiva.
- Corneal xerosis (X2): Dry, hazy cornea.
- Corneal ulceration/keratomalacia (X3A/B): Softening of the cornea, can lead to perforation and blindness.
- Corneal scarring (XS): Late consequence of keratomalacia.
- Fundus changes: Rare; may show retinal pigmentation changes.
B. Extra-Ocular Manifestations:
- Growth retardation in children.
- Increased susceptibility to infections (e.g., measles, diarrhea, respiratory infections).
- Skin changes: Follicular hyperkeratosis (phrynoderma).
- Impaired taste and smell.
- Anemia (due to iron mobilization impairment).
5. Diagnosis
- Clinical diagnosis: Based on ocular findings and dietary history.
- Serum retinol levels: <20 µg/dL suggests deficiency; <10 µg/dL is severe.
- Conjunctival impression cytology: Shows keratinized epithelial cells.
- Electroretinogram (ERG): Reduced rod response in early stages.
6. Management
A. Treatment of Active Deficiency:
- WHO-recommended dosing (oral retinyl palmitate):
- <6 months: 50,000 IU orally on days 1, 2, and 14.
- 6–12 months: 100,000 IU orally on the same schedule.
- 12 months: 200,000 IU orally on the same schedule.
- If corneal involvement (keratomalacia): Same dosing + urgent ophthalmology referral.
B. Management of Complications:
- Topical antibiotic drops for corneal ulcers.
- Supportive care for infections.
- Nutritional rehabilitation.
7. Prevention
- Dietary: Promote vitamin A-rich foods (e.g., dairy products, green leafy vegetables, orange/yellow fruits).
- Supplementation:
- National programs provide periodic high-dose vitamin A to children under 5 years.
- Routine supplementation during measles infection and severe malnutrition.
- Measles vaccination: Reduces the risk of vitamin A deficiency-related blindness.
- Health education: Regarding balanced diet and hygiene.
8. Complications
- Permanent blindness (from corneal scarring).
- Increased child mortality (due to respiratory and gastrointestinal infections).
- Growth retardation and developmental delays.
9. Prognosis
- Early-stage ocular changes (night blindness, Bitot’s spots) are reversible with appropriate treatment.
- Advanced corneal involvement (keratomalacia) often leads to irreversible blindness.
10. Key Points for Exams
- Night blindness is the earliest and most common symptom.
- Bitot’s spots are pathognomonic for vitamin A deficiency.
- WHO classification of xerophthalmia is essential for staging.
- Vitamin A supplementation reduces child mortality by 23-34% in vitamin A-deficient areas.
- Always check for malabsorption syndromes if dietary history is adequate but deficiency persists.
💡 Mnemonic for Ocular Manifestations:
Night blindness → Conjunctival xerosis → Bitot's spots → Corneal xerosis → Keratomalacia (N-C-B-C-K)