A 34-year-old man with KMT2A-MLLT1 acute myeloid leukemia in first complete remission underwent allogeneic peripheral blood stem cell transplantation from his HLA-matched sister after conditioning with busulfan/cyclophosphamide. He did not have severe graft-versus-host disease, but he developed interstitial pneumonia six months after transplantation when his oral cyclosporine A (CsA) dose was reduced to 10 mg/day. He was given prednisolone (PSL), which temporarily improved his respiratory condition, but he quickly deteriorated when PSL was reduced. Anti-MDA5 antibody was found to be positive after additional testing, and a three-drug combination of intravenous cyclophosphamide+PSL+CsA was initiated for anti-MDA5 antibody positive rapidly progressive interstitial lung disease, which was effective for interstitial pneumonia. He received a successful living-donor lung transplant from his younger brother and sister. We present a case of rapidly progressive anti-MDA5 antibody positive interstitial lung disease in which the patient’s respiratory condition improved after triple therapy and subsequent living-donor lung transplantation.
