Follicular bronchiolitis

Last revised by Daniel J Bell on 6 Jan 2022

Follicular bronchiolitis (FB) is a non-neoplastic primary polyclonal B cell hyperplasia of the bronchus-associated lymphoid tissue (BALT) due to chronic exposure to antigens in those with underlying collagen vascular or immune deficiency diseases which usually manifested as small centrilobular ground glass nodules with lower lobe distribution. 

Many cases of follicular bronchiolitis are associated with various systemic illnesses which include

It is defined as lymphoid hyperplasia of the BALT and histologically characterized by polyclonal B cell hyperplasia of the lymphoid follicles with reactive germinal centers principally distributed along bronchioles with only minimal infiltration of alveolar septa.

A key feature described with follicular bronchiolitis on HRCT includes small ground glass centrilobular nodules of 3 mm diameter in lower lobes that are variably associated with peribronchial nodules 1.

Other features, albeit non-specific, include:

Treatment should target the underlying condition, as well as administration of steroids and immunosuppressants. The overall prognosis depends on the underlying or associated abnormality. Some cases may respond to macrolide antibiotics 6.

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