Crohn's disease following rituximab treatment in a patient with refractory nephrotic syndrome.

Rituximab (RTX) is increasingly used for the treatment of refractory nephrotic syndrome due to its inhibitory effect on B cells which extends the period of remission, while lowering the dose of steroids needed for disease management. However, RTX can lead to various side effects, including Crohn's disease. Herein, we describe a case of a 15-year-old boy with refractory nephrotic syndrome diagnosed at age 9 years who developed Crohn's disease following RTX treatment. RTX was initiated in this patient at the age of 13 years 6 months due to occurrence of 12 relapses of nephrotic syndrome over a 4-year period, despite treatment using cyclosporine, steroid pulse therapy, and mycophenolate mofetil. The patient received 4 doses of RTX over a 2-year period (dose, 375 mg/m