Pediatric anti-N-methyl-D-aspartate Receptor Encephalitis Associated with Urothelial Bladder Neoplasm: A case report

•Anti-N-methyl-D-aspartate receptor encephalitis most commonly affects young adults. But in our case, we report a 5-year-old boy.•Anti-N-methyl-D-aspartate receptor encephalitis is related to tumors, such as teratomas of the ovaries. This is the first reported case of anti-NMDAR encephalitis concomitantly occurring in a pediatric patient with newly identified urothelial bladder neoplasms.•Finally, this boy recovered with timely and elaborate intervention. So if a tumor is confirmed, the tumor must be surgically removed immediately.