Abstract
Cystinuria is an autosomal recessive inherited disease that is characterized by the malabsorption of dibasic amino acid and cystine in the epithelial cells of the gastrointestinal tract and renal tubules. It is important to avoid the recurrence of urinary stones, which then progresses to renal failure. A 2-year-old boy presented with gross hematuria at around 10 months of age. He developed macroscopic hematuria and urinary retention again at 13 months, followed by spontaneous passage of the stone. Subsequently he was diagnosed with cystinuria by urinary stone and urine amino acid analysis. Medical management was mainly based on hyperhydration and urine alkalinization with oral sodium bicarbonate to maintain a urine pH>7.5. At the regular checkup 1 years after the initial diagnosis, urinalysis showed microhematuria although he showed normal renal function without any physical symptoms. Abdominal ultrasonography and CT scan demonstrated left ureterohydronephrosis with huge stones at left ureterovesical junction. Because extracorporeal shock wave lithotripsy is not indicated for cystine stones, his stones were removed surgically. Postoperatively, oral α-mercapto-propionylglycine was added to his regimen, continuing urine alkalinization and ensuring adequate urine output. Although it is not easy to ensure a sufficient urinary output in infants and to maintain a low protein diet in order to reduce methionine intake (a prescursor of cystine), the management of cystinuria should focus on avoiding urinary stone formation. Despite urine alkalinization, this patient developed recurrent urinary tract stones. Therefore, we considered that he was at high risk of stone formation and cystine solubilization therapy such as α-mercapto-propionylglycine administration was required. In patients with recurrent episodes of urinary stones, combined pharmacological therapy should be administered as early as possible.
