Renal aminoaciduria is characterized by the abnormally elevated levels of amino acids in the urine, and is usually related to genetic mutations of transport proteins result in the defective reabsorption of free amino acids at the proximal renal tubules. This term does not refer directly to the group of corresponding disease entities but rather to the finding of elevated levels of amino acids in the urine which is inferred to be related to a renal defect rather than to a primary defect of aminoacid metabolism on the basis of other findings.