Abstract Background Epstein-Barr virus (EBV) - associated lymphoproliferative disorders (LPDs) are uncommon in children without prior immunosuppression. Pulmonary involvement is particularly rare and is not usually a presenting feature of LPD even in the setting of inborn errors of immunity (IEI). When present, it can pose substantial diagnostic and therapeutic challenges. We describe a toddler with EBV-positive polymorphic LPD and Pneumocystis jirovecii pneumonia (PJP) as the initial manifestation of an underlying combined immunodeficiency. Case Presentation A 20-month-old male presented with chronic cough, recurrent fevers, and multiple admissions for hypoxemic respiratory failure. His medical history included eczema, developmental delay, dysphagia, and recurrent viral infections. Immunologic evaluation showed evidence of both antibody and T -cell dysfunction, with low immunoglobulin (Ig)G and IgM, elevated IgA and IgE, reduced B cells lacking mature memory cells, very low natural killer T cells, and poor T cell proliferative response on stimulation testing. Chest CT revealed innumerable bilateral pulmonary nodules with hilar and mediastinal lymphadenopathy. Lung biopsy confirmed EBV-positive polymorphic LPD with coexistent Pneumocystis jirovecii pneumonia. Whole exome sequencing and chromosomal microarray identified variants of unknown significance. Treatment included intravenous trimethoprim-sulfamethoxazole and corticosteroids for PJP, 4 doses of weekly rituximab (375 mg/m²) and intravenous immunoglobulin (IVIG). A PET-CT obtained after completion of 4 doses of rituximab therapy showed near-complete resolution of pulmonary nodules and lymphadenopathy. Given this favorable response, he received two additional consolidative doses of rituximab. The patient remains clinically stable. Hematopoietic stem cell transplantation is being considered for definitive immune reconstitution. Discussion This case demonstrates that pulmonary LPD, although rarely described as a presenting feature of EBV-driven disease in IEI, can occur as the dominant manifestation. Recognition of this atypical presentation and early immunologic evaluation are essential for diagnosis and successful targeted therapy. - EBV-associated polymorphic LPD with concurrent PJP can reveal previously unrecognized immune dysregulation even when genetic testing is inconclusive. Awareness of this rare pulmonary presentation enables timely diagnosis, appropriate immunologic workup, and effective management, including consideration of curative transplantation. This abstract is funded by: None
Alza’Atreh et al. (Fri,) studied this question.