Chronic rejection (or Bronchiolitis Obliterans syndrome-BOS) is a major cause of mortality
and morbidity after lung transplantation. Because montelukast has been shown to be of some
efficacy in a similar disease (Obliterative Bronchiolitis after bone marrow transplantation),
the investigators would like to test if montelukast can indeed slow down the progression of
chronic rejection after lung transplantation.