Late-Onset Acute Cellular Rejection after Lung Transplantation Triggered by a Fluctuation in the Tacrolimus Trough...

Acute cellular rejection (ACR) usually develops within the first year of lung transplantation. We report a case of biopsy-proven ACR occurring 18 months post-transplant that was successfully treated with steroid pulse therapy and intensified immunosuppression. Onset followed azithromycin and clofazimine for Mycobacterium abscessus, which caused the tacrolimus trough levels to drop. The patient presented with dyspnea, diffuse ground-glass opacities, and reduced lung function. Although C4d staining was positive, the absence of donor-specific antibodies and histological findings supported the diagnosis of ACR. This case highlights the need for careful monitoring of tacrolimus trough levels and a comprehensive diagnostic workup to ensure the timely and appropriate treatment of late-onset rejection.