The aminoacid excreted in Hartnup's disease is -

Ans. is 'c' i.e., Tryptophan* Hartnup's disease is caused by a defect of a neutral aminoacid transporter which is specific for tryptophan absorption along intestine and tryptophan reabsorption along renal tubules.* Tryptophan malabsorption leads to tryptophan deficiency* As tryptophan is necessary for formation of niacin, Hartnup's disease presents with niacin deficiency manifestations or pellagra.# Photosensitive Dermatitis# Diarrhoea# Psychiatric manifestations - anxiety, mood changes, delusions, hallucinations* As niacin is necessary for insertion of neutral aminoacid transporters into the renal tubules, Hartnup's disease presents with aminoaciduria . There is increased excretion of neutral aminoacids like :# Tryptophan# Isoleucine# Phenyalanine# Histidine# Leucine# Lysine* Characteristically in aminoaciduria due to hartnup s disease, levels of proline, hydroxyproline and arginine levels are normal. This differentiates Hartup's disease aminoaciduria from fanconi's syndrome* Onset of presentation is variable. Infants with Hartnup's disease present with failure to thrive, ataxia, nystagmus.* As when tryptophan gets oxidised, the indole ring is released, Obermeyer's test or test for urinary Indican is positive.