However, some patients develop slowly progressive disease, for which the clinical markers include Continued smoking Age extremes Multiorgan involvement Persistent constitutional symptoms Numerous cysts on chest x-ray Reduced DLCO Low forced expiratory volume in 1 second (FEV1) / forced vital capacity (FVC) ratio (< 66%) High residual volume (RV) / total lung capacity (TLC) ratio (> 33%) Need for prolonged corticosteroid use Cause of death is respiratory insufficiency or cancer.