Ustekinumab in Treatment of Refractory Paediatric Crohn Disease

To the Editor: We read with interest the publication by Rinawi et al on their successful use of ustekinumab in a child with resistant Crohn disease (1). We wish to present our experience in a 16-year-old boy with panenteric Crohn disease. Our patient was diagnosed at 11 years. The patient had refractory disease, which failed to respond to thiopurines or methotrexate. Clinical and biochemical remission (including C-reactive protein normalisation) was obtained on infliximab; however, a subsequent secondary loss of response occurred. In an effort to regain response, dose escalation was given, resulting in an infusion reaction and subsequent infliximab treatment cessation. Adalimumab also showed no significant treatment effect. At this point, the patient was steroid dependent despite methotrexate 25 mg and weekly adalimumab 40 mg; Pediatric Crohn Disease Activity Index was 42.5, with endoscopic evidence of active ileocolonic disease and raised inflammatory markers. Given the patient's initial response to infliximab and high C-reactive protein, it was felt that the patient may respond to ustekinumab (2,3). The patient received 1 subcutaneous induction dose of 180 mg (3 mg/kg) and then 90 mg (1.5 mg/kg) at week 2. Unfortunately, there was no significant improvement at 10 weeks, so a colectomy and an end ileostomy were performed, resulting in clinical remission. Unlike the previous case where ustekinumab resulted in a rapid improvement in symptoms, we did not observe a similar response despite similar dosing and schedule. The explanation for lack of response is unclear given the favourable indicators for response in our patient. Further use of ustekinumab in the paediatric population may provide further insight into who will benefit.