<prompt> Hanup disease is mainly due to:Niacin deficiencyDefective transpo of tryptophanDefective serotonin biosynthesisThiamine deficiency  <response>: Hanups disease is an autosomal recessive disorder, in which there is: Defect in neutral amino acid transpoer tryptophan Failure to absorb tryptophan from intestine and also reabsorb it from kidneys Clinical feature: Aminoaciduria i.e. tryptophan in urine Pellagra niacin deficiency like symptoms neurological and dermatologic, despite an adequate intake of both tryptophan and niacin. NORMAL AND ABNORMAL ROUTES OF TRYPTOPHAN METABOLISM 