| Probable |
| Acute rejection |
| Lymphocytic bronchitis/bronchiolitis |
| CMV pneumonitis |
| Medication noncompliance |
| Primary graft dysfunction |
| Potential |
| CMV infection (without pneumonitis) |
| Organizing pneumonia |
| Recurrent infection other than CMV |
| Older donor age |
| Prolonged allograft ischemia |
| Donor-specific HLA antibodies |
| Gastroesophageal reflux |
| HLA-mismatching |
| Underlying cause of lung disease |
