GVHD leads to increased morbidity and mortality after allogeneic hematopoietic SCT (HCT). 1 Compared with myeloablative regimens (MARs), nonmyeloablative conditioning regimens do not appear to decrease the rate of serious GVHD. 2 In steroid-resistant patients, various immunosuppressive agents including antibodies against IL-2 and TNF have been attempted. [3][4][5] Outcome is very poor in patients who do not respond second-line treatment, in particular, if they have gut GVHD. Non-relapse mortality was 71% at 1-year post-HCT in patients with steroid-refractory gut GVHD. 6 Survival rate decreases to 16% in adults not responding to steroids within 2 weeks 6 or 0% in adults and children not responding to a combination of anti-IL-2 and anti-TNF. 3,4 A second HCT from another donor could improve gut GVHD in mice. 7 We performed an HCT from a second HLA-matched sibling for treatment of severe acute gut GVHD in a patient in whom all other therapeutic approaches had been exhausted.A 31-year-old man with wt loss and bone pain in his legs, presented with a WBC count 6.7 Â 10 9 /l, 14% blasts, hemoglobin 9.8 g per 100 ml, and plt count 154 000 Â 10 9 /l. A BM biopsy revealed 4 þ reticulin fibrosis and 16% myeloblasts, consistent with advanced stage primary myelofibrosis. He was initially treated with lenalidomide and then a panhistone deacetylase inhibitor (LBH589). He received an HCT from his 22-year-old brother after treatment with melphalan (140 mg/m 2 ) and fludarabine (120 mg/m 2 ). He was treated with tacrolimus (0.03 mg/kg/day i.v. continuous infusion), initiated day À2 and mycophenolate mofetil (1 g i.v. b.i.d.) initiated day 0. He received G-CSF, acyclovir, fluconazole and levofloxacin. On day þ 7, he developed clinical grade III gut GVHD (1.5-2 l/d of diarrhea). Four days after initiating treatment with methylprednisolone (1 mg/kg i.v. b.i.d.) and total parenteral nutrition, his symptoms resolved. Neutrophil and plt engraftment occurred on days þ 10 and þ 42, respectively. Chimerism analysis revealed 100% donor-derived cells on day þ 14. Steroids were tapered off within 4 months. At 5 months post transplant, he developed recurrent gut GVHD with severe abdominal pain and 1.5 l of diarrhea per day. Colonic biopsy revealed extensive mucosal ulceration and complete crypt loss, consistent with severe (grade IV) acute GVHD (Figure 1). High-dose therapy with methylprednisolone, infliximab (anti-TNF) and daclizumab (anti-IL-2) did not improve GVHD. Severe gut GVHD persisted despite sequential treatment with extracorporeal photopheresis, rituximab, CY and pentostatin.A second HCT from another donor for treatment of steroidresistant GVHD was proposed to him and his family. Although this approach had not been used for this purpose, previously, he offered his consent for the procedure, and our institutional ethical committee approved the second transplant. He received a second transplant from his HLAidentical youngest brother (13 years old) 3 months after recurrence of gut GVHD. The conditioning regimen consisted of CY (60 mg/...