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Vitamin A Deficiency
📖 Overview
- 🌍 A major global health problem in Asia, Africa, and China where chronic dietary insufficiency is common.
- 👶 Especially harmful in children, worsening outcomes when combined with diarrhoea, measles, malaria, or respiratory infections → contributes to high childhood mortality.
- ⚠️ Preventable cause of childhood blindness worldwide.
🧬 Aetiology & Physiology
- Vitamin A is crucial for synthesizing rhodopsin in the retina → required for night vision 🌙.
- Biochemical pathway:
All-trans retinol ➡️ 11-cis retinal ➡️ Rhodopsin ➡️ All-trans retinal (light absorption cycle). - Deficiency arises from:
- 🥗 Inadequate intake (low fruit, vegetables, animal products).
- ⚡ Malabsorption (e.g., coeliac disease, pancreatic insufficiency).
- 🤒 Increased requirements (chronic infections, measles).
👁️ Clinical Presentation
- 🌙 Night Blindness (Nyctalopia): poor dark adaptation, early sign.
- 👀 Xerophthalmia: dry conjunctiva & cornea from reduced mucous secretion.
- ⚪ Bitot’s Spots: foamy, keratinised plaques on conjunctiva → pathognomonic.
- 🪟 Keratomalacia: corneal softening/ulceration → irreversible blindness if untreated.
- 🧴 Skin: follicular hyperkeratosis (“gooseflesh” skin), rough scaly patches.
- 🦠 Immune dysfunction: ↑ infections (diarrhoea, measles, pneumonia).
🧪 Investigations
- 📉 Serum retinol < 0.7 µmol/L confirms deficiency.
- 🧫 Conjunctival impression cytology: shows loss of goblet cells & keratinisation.
- 📊 Assess dietary intake and coexisting malnutrition.
💊 Management
- ✅ Vitamin A supplementation:
- WHO recommends high-dose oral vitamin A in endemic regions (200,000 IU in children >1 year).
- Proven to ↓ childhood mortality by up to 23% in deficiency settings.
- 🥗 Improve dietary intake: carrots, spinach, sweet potatoes, liver, eggs, fortified foods.
- 💉 Treat underlying infections (measles, diarrhoea) to break the cycle of malnutrition.
📈 Prognosis
- ⚠️ Untreated → blindness, recurrent infections, ↑ mortality.
- ✅ Supplementation & dietary improvement → reverses early changes, prevents keratomalacia.
📚 References
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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