Eosinophilic cystitis mimicking hemorrhagic cystitis in relapsed follicular lymphoma

Eosinophilic cystitis (EC) is a rare and non-infectious inflammatory disorder characterized by transmural infiltration of eosinophils in the bladder wall. The diagnosis of EC is made only by the pathophysiological findings. Because the urinary symptoms of EC are quite similar to other urinary tract disorders including hemorrhagic cystitis (HC), it can be misdiagnosed or left undiagnosed. A 49-year-old woman with relapsed and refractory follicular lymphoma presented with sudden-onset gross hematuria after the chemo-immunotherapy. The patient was initially treated as HC with continuous bladder irrigation, resulting in recurrent and refractory hematuria. Corticosteroid dramatically resolved hematuria after the bladder biopsy revealed EC. It is important to suspect EC and perform bladder biopsy in patients with recurrent episodes of hematuria or refractory to conservative treatment for HC.