Does latent tuberculosis (TB) cause a tree-in-bud pattern?

From the Guidelines

Latent TB does not cause tree-in-bud pattern on imaging, as this finding is typically associated with active TB infection, not latent TB. Tree-in-bud is a radiological finding typically seen on chest CT scans that represents small centrilobular nodules with branching opacities resembling a budding tree, and is often indicative of endobronchial spread of infection, as described in the study by 1. According to the study, CT findings can show distinct findings such as cavitation or endobronchial spread with tree-in-bud nodules, which is helpful in cases where chest radiography does not show classic findings of TB 1. Some key points to consider include:

• Latent TB infection (LTBI) is asymptomatic and shows no radiological abnormalities on imaging studies, as the bacteria remain dormant within the body, contained by the immune system 1.
• The tree-in-bud pattern specifically indicates active endobronchial spread of infection, which occurs when TB bacteria actively multiply and spread through small airways, and can also be seen in other conditions like bronchiolitis, bronchiectasis, or other infectious bronchiolitis.
• If a patient with latent TB has imaging that shows a tree-in-bud pattern, this suggests either progression to active TB or another concurrent respiratory condition that requires prompt medical evaluation, as noted in the study by 1. In terms of imaging modalities, CT is often used to increase the specificity of the diagnosis of TB, and can be helpful in identifying patients with latent TB who will be at risk for reactivation disease, as described in the study by 1.

From the Research

Latent TB and Tree-in-Bud Pattern

• The tree-in-bud pattern is a radiologic finding that can be associated with various lung diseases, including infections, congenital disorders, and immunologic disorders 2.
• Latent tuberculosis infection (LTBI) is a condition where a person is infected with Mycobacterium tuberculosis, but does not show any symptoms of active tuberculosis.
• The provided studies do not directly address the relationship between latent TB and the tree-in-bud pattern.
• However, one study mentions that the tree-in-bud pattern was originally reported in cases of endobronchial spread of Mycobacterium tuberculosis 2.
• Other studies discuss the treatment of LTBI, including the use of isoniazid and rifapentine, but do not mention the tree-in-bud pattern 3, 4, 5.
• A study on the treatment strategy for rifampin-susceptible tuberculosis also does not mention the tree-in-bud pattern 6.

Treatment of Latent TB

• The treatment of LTBI is an essential component of tuberculosis control and elimination 3.
• Various treatment regimens have been studied, including 9 months of isoniazid, 4 months of rifampin, and 3 months of isoniazid-rifapentine 3, 4, 5.
• These studies have shown that shorter treatment regimens can be as effective as longer regimens, with higher treatment completion rates and fewer adverse events 3, 4, 5.

Radiologic Findings

• The tree-in-bud pattern is a specific radiologic finding that can be seen on thin-section CT scans of the lungs 2.
• It is characterized by small centrilobular nodules connected to branching linear structures, and can be associated with various lung diseases 2.
• While the provided studies do not directly address the relationship between latent TB and the tree-in-bud pattern, they do highlight the importance of radiologic findings in diagnosing and managing lung diseases 2.