Bronchiolitis Obliterans in Unicentric Castleman Disease Without Paraneoplastic Pemphigus Requiring Bilateral Lung Transplantation.

Bronchiolitis obliterans (BO) is an uncommon but life-threatening complication of unicentric Castleman disease (UCD), typically linked to paraneoplastic pemphigus. We report a 25-year-old woman who developed progressive dyspnea and severe, irreversible airflow obstruction in the absence of clinical or serologic evidence of paraneoplastic pemphigus. Unresponsive to inhaled triple therapy and systemic corticosteroids, she progressed to end-stage respiratory failure. She underwent living-donor bilateral lung transplantation with subsequent excision of the retroperitoneal UCD lesion. Explanted lungs confirmed concentric obliteration of small airways consistent with BO. Post-transplant, she demonstrated marked functional improvement with no recurrence of BO or UCD. This case highlights that BO can occur without detectable paraneoplastic pemphigus autoantibodies and that lung transplantation remains the only curative option for the end-stage disease.