Clinical features of allogeneic hematopoietic stem cell transplantation-associated organizing pneumonia.

We describe the clinical courses and outcomes of allogeneic hematopoietic stem cell transplantation-associated organizing pneumonia (HOP) observed in our institution over the past 20 years. Charts and chest radiographs of 603 allogeneic transplant recipients were retrospectively reviewed for HOP. In total, 12 cases of HOP were identified (2.0%) at a median interval of 148 days after transplantation (range, 53-475 days), presenting with low-grade fever, nonproductive cough and dyspnea at onset. Initial antibiotic treatment did not ameliorate symptoms, but most patients responded well to 0.5-1 mg/kg of prednisolone. HOP flare-up occurred after discontinuing treatment or while tapering doses in 9 of 12 patients, but responded to re-treatment with the initial dose of steroid. Although three patients died, no deaths were attributable to pulmonary failure. The remaining nine patients displayed no relapse of primary disease and 5-year survival rate was 74.1%. Clinical features of the 12 patients were similar in that all underwent irradiation-containing conditioning and most had a prior history of acute graft-versus-host disease (GVHD) and cytomegalovirus (CMV) infection. Furthermore, eight patients had active chronic GVHD at onset of HOP. These findings suggest that factors such as irradiation-containing regimens, previous CMV infection and allogeneic immune reaction may contribute to HOP occurrence.