Tree-in-bud nodularity

Background

CT chest finding
Pattern may be related to distal airways (more common) or distal pulmonary vasculature

Infection: mycobacterial (predominately TB but also NTM), bacterial (particularly Staphylococcus aureus), viral (particularly CMV), fungal (invasive aspergillosis)
Congenital: cystic fibrosis and Kartagener syndrome
Idiopathic: bronchiolitis obliterans, diffuse panbronchiolitis
Aspiration
Allergic bronchopulmonary aspergillosis
Autoimmune: rheumatoid arthritis, Sjögren syndrome
Vascular: peripheral pulmonary vascular disease (neoplastic pulmonary emboli)