Which microscopic findings are characteristic of chronic lung transplantation rejection?

Updated: Jun 06, 2019
  • Author: Aliya N Husain, MBBS, MD; Chief Editor: Philip T Cagle, MD  more...
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Chronic rejection

Chronic rejection usually occurs after 1 year posttransplantation but may be seen as early as within a few weeks. It is the most significant complication limiting long-term survival, affecting up to 50% of patients at 3 years posttransplantation. A previous episode of acute rejection is the most well-recognized risk factor.

Persistent significant decreases on lung function tests are the most reliable method to diagnose chronic rejection (clinically termed bronchiolitis obliterans syndrome). It manifests pathologically as BO, a chronic, progressive fibroinflammatory occlusion of small airways.

The pathogenic mechanism of chronic rejection is poorly understood, but it is thought to result from the monocyte/macrophage system with the airway epithelium, with upregulation of major histocompatibility complex (MHC) antigens, co-stimulatory molecules, and adhesion molecules, leading to an outpouring of inflammatory and fibroproliferative mediators. Chronic rejection should be suspected with an insidious onset of generalized symptoms, including cough and dyspnea with a progressive decline on pulmonary function tests.

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