Hartnup's Disease
• There is a defect in the transport of neutral amino acids (monobasic-monocarboxylic amino acids; alanine, serine, threonine, valine, leucine, isoleucine, phenylalanine, tyrosine, tryptophan) through the small intestine mucosa and renal tubules. It is autosomal recessive.
• Clinical findings occur due to impaired intestinal absorption of nicotinic acid (Niacin) and tryptophan, a precursor of nicotinamide. Similar to pellagra, photosensitivity of the skin and dermatitis in sun-exposed areas are major symptoms. There is cerebellar ataxia.
• Mental development is usually normal. In some cases, emotional disorders, depression, and suicidal tendencies may occur.
• Neutral aminoaciduria is seen in the urine; however, unlike Fanconi syndrome, arginine and proline are not detected in the urine.
• Nicotinamide, which is given twice the daily dose in symptomatic patients, controls skin and neurological findings. The diet of patients should be high in protein.