Non-bronchiolitis obliterans syndrome forms of chronic lung allograft dysfunction

The bronchiolitis obliterans syndrome (BOS) has been described as the clinical correlate of chronic lung allograft rejection and defi ned as irreversible airfl ow obstruction in the absence of other causes. However, it has become apparent that BOS does not explain all chronic lung allograft dysfunction (CLAD) and that a variety of other etiologies with a mixed obstructive and restrictive pattern on spirometry, or even a pure restrictive picture (restrictive allograft syndrome, or RAS), are also identifi able. Surgical, mechanical, vascular obstructive, infectious, and infi ltrative processes, as well as a whole range of chronic lung allograft rejection entities need to be considered in making a diagnosis of CLAD. The performance of any lung allograft is really the sum-of-the-parts of all of these processes, and considering non-BOS CLAD in all its forms may potentially provide more therapeutic options than just considering BOS alone as the explanation for declining lung function.