Hanup disease is mainly due to:

Hanup's 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