The “tree-in-bud” pattern in HRCT is characterized by tiny, hypodense centrilobular nodules connected to multiple branching linear structures arising from a single bronchiole. Active pulmonary tuberculosis with endobronchial spread is one of the most common causes of this radiological pattern. The right upper lobe and right main bronchus are the common locations for the involvement; however, here, in our case, diffuse involvement can be appreciated in bilateral lung fields.

Sputum for acid-fast bacilli (AFB) was performed, which revealed Mycobacterium tuberculosis bacteria as the causative agent for these lesions.