Disorders of infancy accounted for 56.3%, including bronchopulmonary dysplasia (BPD) (52.4%) and secondary pulmnary hypoplasia (3.9%); primary lung disorders of the immunocompetent host were 34.1%, including postinfectious bronchiolitis obliterans (PIBO) (25.3%), specific infections (3.9%), idiopathic pulmonary hemosiderosis (IPH) (3.9%), and nonspecific interstitial pneumonia (1%); disorders of the immunocompromised host (1%); vascular disorders masquerading as interstitial lung disease (1%); and unclassified (7.8%).