BRIEF REPORT Cryptogenic organizing pneumonia after rituximab therapy for presumed post-kidney transplant lymphoproliferative disease Martin Bitzan & Jodie D. Ouahed & Lucy Carpineta & Chantal Bernard & Lorraine E. Bell Received: 10 September 2009 / Revised: 12 December 2009 / Accepted: 16 December 2009 / Published online: 6 February 2010 # IPNA 2010 Abstract Cryptogenic organizing pneumonia (COP, for- merly bronchiolitis obliterans organizing pneumonia) is rare in children. We describe an 11-year-old girl with Epstein–Barr virus (EBV) reactivation/presumed post- transplant lymphoproliferative disease (PTLD) 15 months after undergoing a deceased donor kidney transplanta- tion. Treatment with reduced immunosuppression, gan- ciclovir, and cytomegalovirus immunoglobulin was complicated by severe graft rejection, prompting therapy with methylprednisolone, anti-thymocyte globulin and four weekly doses of rituximab (total 1500 mg/m 2 ). Tacrolimus- and prednisone-based anti-rejection prophy- laxis was complemented with low-dose sirolimus. When the lactate dehydrogenase and uric acid levels rose 10 weeks after the first rituximab infusion and bilateral pulmonary nodules were detected by computerized tomography, recurrence of PTLD was suspected. Open lung biopsy of the clinically asymptomatic patient identified the nodules as COP, characterized by abundant CD3 + T-cells, few B-cells, and the absence of EBV, cytomegalovirus, or adenovirus antigens. With normaliza- tion of the peripheral B-cell count, EB viremia reappeared and persisted, despite minimal immunosuppression. Four years later, the patient was diagnosed with classical Hodgkin lymphoma-type PTLD with multiple pulmonary and abdominal nodes. This first report of rituximab- associated, pediatric COP highlights the risk of pulmonary complications after treatment with B-cell depleting agents in solid organ transplant recipients, and the importance of a histopathologic diagnosis and vigilant follow-up of such lesions. Keywords Bronchiolitis obliterans organizing pneumonia . COP . EBV . Hodgkin’ s lymphoma . Pediatric . Post-transplant lymphoproliferative disease . PTLD . Rituximab . Sirolimus Introduction Cryptogenic organizing pneumonia (COP), previously known as bronchiolitis obliterans organizing pneumonia (BOOP), typically presents in the fifth decade of life with an influenza-like illness, persistent dry cough, fever and dyspnea, and bilateral patchy airspace consolidation visible by imaging [1–3]. A lung biopsy is required for a definitive diagnosis [2]. Asymptomatic or insidious manifestations have been described [1, 3]. Glucocorticoids are part of the treatment regimen, but spontaneous recovery may occur [3– 5]. Post-transplant lymphoproliferative disease (PTLD) refers to a state of unregulated proliferation of Epstein– M. Bitzan (*) : J. D. Ouahed : L. E. Bell Division of Nephrology, Montreal Children’ s Hospital, McGill University, 2300, rue Tupper E-222, Montréal, Québec H3P 1P3, Canada e-mail: martin.bitzan@mcgill.ca L. Carpineta Department of Medical Imaging, Montreal Children's Hospital, McGill University, Montréal, Québec H3P 1P3, Canada C. Bernard Department of Pathology, Montreal Children’ s Hospital, McGill University, Montréal, Québec H3P 1P3, Canada Present Address: J. D. Ouahed McMaster University Pediatrics Program, McMaster Children’ s Hospital, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada Pediatr Nephrol (2010) 25:1163–1167 DOI 10.1007/s00467-010-1447-8