A 54-year-old male was diagnosed with Philadelphia (-) acute B lymphoblastic leukemia in 2015. A relapse with central nervous system involvement was demonstrated 4 months after ending Hyper CVAD chemotherapy. He received intrathecal methotrexate with FLAGIDA chemotherapy achieving a second complete remission (CR) followed by a haploidentical myeloablative transplant with cyclophosphamide and total body irradiation (TBI) using peripheral blood hematopoietic stem cell transplantation (PBSCT) from a 3/6 HLA matched sibling. GVHD prophylaxis consisted of post transplant cyclophosphamide (days +3 and +4), tacrolimus and mycophenolate mofetil. 1 week post transplantation he developed febrile neutropenia and a progressive hepatic failure. After engraftment on day 12, he developed a progressive respiratory failure and required invasive mechanical ventilation. At day 14 an evanescent rash was noticed and the skin biopsy showed grade 3 aGVHD. Chest CT Scan showed an interstitial pattern of infiltration without images suggesting fungal infection. BAL was performed an all assays were negative (bacterial cultures, CMV PCR, EBV PCR, aspergillus test, no cardial test). He was started on high doses of methylprednisolone (1.5 g total dose) followed by prednisone 2 mg/kg/day without improvement after 14 days of treatment. A diagnosis of corticoid refractory acute GVHD NIH grade 3 was established and EP was started. During the first session of apheresis, his respiratory function worsened. We started low doses of ruxolitinib (5 mg BID), and after 2 weeks of treatment all cutaneous and hepatic alterations resolved and chest CT scan showed a significant resolution of the interstitial pattern. This allowed the weaning of the 2-month mechanical ventilation. After 12 months of treatment the patient have normal lung function and no other signs of GVHD nor leukemia relapse (Fig. 1).