Ruxolitinib for Treating Steroid-Refractory Acute Graft-Versus-Host Disease in an Infant with Malignant Osteopetrosis Who Received Double-Unit Umbilical Cord Blood Transplantation

Abstract

A 3-month-old male infant was transferred to our hospital due to bicytopenia. His bone marrow biopsy showed irregular bony trabeculae with cartilaginous core, which was consistent with osteopetrosis. In the genetic test, c.242del (p.Pro81Argfs*85) in TCIRG1 was found to be homozygotic, thus he was diagnosed with malignant infantile osteopetrosis. At 6 months of age, he received double-unit umbilical cord blood transplantation (UCBT) with the conditioning regimen including busulfan, cyclophosphamide, and rabbit anti-thymocyte globulin. Initially, single UCB was infused to the patient, but the post infusion viability of the UCB was unexpectedly low. Thus, another UCB was additionally infused. Cyclosporine and mycophenolate mofetil were used for graft-versus-host disease (GVHD) prophylaxis. Neutrophils and platelets were engrafted on day +13 and +33, respectively. With engraftment, he showed overall grade 4 acute GVHD involving the skin and gut, which was refractory to corticosteroids. Despite treating with low-dose weekly methotrexate (10 mg/m2) and oral beclomethasone, his symptoms persisted. After treating with ruxolitinib 2.5 mg/day for 2 weeks, and 5 mg/day thereafter, his diarrhea stopped in 2 weeks and his skin symptoms gradually improved over 3 months. The short tandem repeats showed 100% donor chimerism at 1 and 3 months after UCBT. Currently, 4 months after UCBT, he is 10 months old. The oral prednisolone has been tapered to 0.6 mg/kg/day, and the dose of ruxolitinib was decreased to 2.5 mg/day without recurrence of GVHD. We plan to taper off the immunosuppressive agents if his GVHD symptoms do not recur.