⚠️ The classic mnemonic for pellagra = the four Ds: Dermatitis, Diarrhoea, Dementia → Death. 📜 Historically, it was thought to be an infectious disease until the early 20th century.

ℹ️ About

🔬 Pellagra = deficiency of niacin (Vitamin B3) or its precursor tryptophan.
🍽️ Results from inadequate dietary intake or impaired metabolism.
📖 Name derived from Italian “pelle agra” = “rough skin”.
🧪 First B-vitamin identified was thiamine, but pellagra highlights niacin’s role in metabolism.

⚠️ Causes / Risk Factors

🌽 Maize/corn-based diets (low in tryptophan & niacin unless treated with alkali)
🍷 Alcoholism, anorexia, severe malnutrition
🧬 Malabsorption & chronic GI disease
💊 Drugs: Isoniazid (inhibits conversion of tryptophan → niacin)
🏥 Hypercatabolic states (infection, adrenal phaeochromocytoma, malignancy)

🧬 Aetiology

Niacin is required for synthesis of NAD and NADP, essential cofactors in oxidative metabolism.
Critical for energy production in all living cells.
Some hepatic storage exists but limited.
💉 Pharmacological niacin lowers LDL & VLDL cholesterol.

📂 Types

🥗 Primary pellagra: Dietary deficiency of niacin/tryptophan.
🧪 Secondary pellagra: Due to impaired absorption, metabolism, or increased demand (alcoholism, isoniazid therapy, chronic illness).

💊 Pearl: Pellagra is a recognised complication of isoniazid therapy, which blocks tryptophan → niacin conversion.

🩺 Clinical Features

👅 Glossitis, angular stomatitis, pigmented & scaling rash (esp. sun-exposed areas)
🍽️ Anorexia, irritability, abdominal pain, diarrhoea, vomiting
🩸 Mucosal involvement: vaginitis, oesophagitis
🌞 Dermatitis: photosensitive rash, Casal’s necklace around the neck (pathognomonic)
🧠 Neuro: irritability → depression → progressive dementia
☠️ Untreated disease progresses to death

🔎 Investigations

🩸 Anaemia (often microcytic hypochromic)
⬆️ Hyperhomocysteinaemia (due to impaired NAD metabolism)
📉 Low serum niacin levels (confirmatory)

💊 Management

💊 Oral nicotinamide supplementation (dramatic clinical improvement in days–weeks)
🥗 Optimise overall nutrition: protein, vitamins, and minerals
🌽 Public health: maize flour fortification with nicotinamide for long-term prevention

📌 Exam Pearl: Pellagra = think of “corn diet + 4Ds”. In clinical practice, always ask about alcohol use, nutrition, and isoniazid therapy.

📚 References

WHO: Pellagra – Prevention and Control in Major Emergencies

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Niacin deficiency (Pellagra Vitamin B3)