Eosinophilic cystitis (EC) is rather an uncommon disease in childhood. A ca
se of EC in a 5-year-old boy. in which open biopsy was needed for final dia
gnosis, is reported. After diagnosis, he was treated with pemirolast potass
ium followed-up with eosinophil cationic protein (ECP) in serum and urine.
Eosinophil cationic protein is an appropriate marker of EC.