Abstract
We report a 20-day-old boy with Cornelia de Lange syndrome. He had high urinary β2-microglobulin from the neonatal period. At six months of age, he was affected with urinary tract infection again, and vesico-ureteral reflux was discovered. Combined treatment with cefaclor and sulf amethoxazole/trimethoprim had been used in repeated urinary tract infection. Repeated urinalysis and measurement of urinary β2-microglobulin were useful for diagnosis and assessment of the disease.