Hartnup's syndrome is an autosomal recessive disorder causing poor absorption of which amino acids, potentially producing pellagra-like dermatitis, diarrhea and dementia?

• A. Basic amino acids
• B. Aromatic amino acids
• C. Essential amino acids
• D. Branched-chain amino acids

Answer: (A)

Hartnup disease stems from a defect in the intestinal and renal transporter for neutral amino acids, leading to poor absorption of these amino acids, especially tryptophan. Tryptophan is an essential amino acid and a precursor for niacin (vitamin B3) synthesis. When tryptophan absorption is impaired, niacin production can fall, causing pellagra-like dermatitis, diarrhea, and dementia. Among the options, aromatic amino acids encompass tryptophan, making aromatic amino acids the most accurate choice. Basic amino acids (lysine, arginine, histidine), branched-chain amino acids (valine, leucine, isoleucine), and the broader category of essential amino acids do not specifically reflect the transporter defect in Hartnup disease.