The defective gene controls the absorption of certain amino acids from the intestine and the reabsorption of those amino acids in the kidneys. Consequently, a person with<unk>  cannot absorb amino acids properly from the intestine and cannot reabsorb them properly from tubules in the kidneys. Excessive amounts of amino acids, such as tryptophan, are excreted in the urine. The body is thus left with inadequate amounts of amino acids, which are the building blocks of proteins. With too little tryptophan in the blood, the body is unable to make a sufficient amount of the B-complex vitamin niacinamide, particularly under stress when more vitamins are needed. In<unk> , urinary excretion of proline, hydroxyproline, and arginine remains unchanged, differentiating it from other causes of generalized aminoaciduria, such as Fanconi syndrome. With urine chromatography, increased levels of neutral amino acids (e.g., glutamine, valine, phenylalanine, leucine, asparagine, citrulline, isoleucine, threonine, alanine, serine, histidine, tyrosine, tryptophan) and indican are found in the urine. Increased urinary Indican can be tested by Obermeyer test.
Hartnup disease
Trevor disease
Hirschsprung's disease
Meckel's diverticulum
Mirizzi's syndrome
Killian–Jamieson diverticulum
Cimino fistula
Urachal diverticulum