49,XXXXY syndrome with hydronephrosis caused by intravesical ureterocele.

A 1-month-old boy was referred to our hospital with right hydronephrosis. Excretory urography showed poor visualization of the right kidney and a filling defect in the bladder. Chromosomal analysis of peripheral blood revealed a karyotype of 49,XXXXY, and a diagnosis of 49,XXXXY Klinefelter s syndrome associated with hydronephrosis caused by intravesical ureterocele was made. 49,XXXXY Klinefelter s syndrome with anomalies of the urinary tract is extremely rare, and only 2 cases have been reported so far.