Abstract
We reported a case of cystinuria with delayed psychomotor development. According to oral cystine and lysine loading studies in the patient and his parents, we estimated that he was the double heterozygote of type I-III. The relationship between cystinuria and delayed psychomotor development was unclear. The disturbance of active transport in placenta or brain may have caused the deficiency of essential amino acids and consequently delayed psychomotor development, because cystinuria has been known as an inheritable disorder of cystine and dibasic amino acids affecting the epithelial cells of the renal tubules and the gastrointestinal tract.
