[A case of Prader-Willi syndrome accompanied with a renal stone].

Little information is available regarding the correlation between Prader-Willi syndrome and urolithiasis. We report a patient with Prader-Willi syndrome with a renal uric acid (UA) stone. A 23-year-old male patient was admitted to our department with gross hematuria and left flank pain. The blood and urine examination demonstrated hyperuricemia with the presence of UA crystals in the urine. Excretory urography revealed a radiolucent stone (17 x 27 mm) in the left renal pelvis suggesting a UA stone. The stone was removed successfully using extracorporeal shockwave lithotripsy (ESWL) combined with medication for UA metabolism. The stone was thought to have formed as a result of overeating associated with Prader-Willi syndrome, and accompanying overproduction of purine.