Introduction: Follicular bronchiolitis (FB) is a rare type of cellular bronchiolitis characterised by the presence of hyperplastic lymphoid follicles with reactive germinal centres, distributed along the bronchovascular bundles.
Observation: A non-smoking 36 year old woman was seen because of progressive exertional dyspnoea for 2 years. Chest x-ray and lung CT scan were normal. Pulmonary function tests revealed irreversible airflow obstruction. Exercise testing showed a ventilatory limitation of aerobic capacity with limitation of volume recruitment. The diagnosis of FB was obtained by surgical biopsy. A deficiency of immunoglobulins G4 and M was found.
Conclusion: The main clinical manifestation of FB is exertional dyspnoea in a young patient. The lung CT scan frequently shows peripheral micronodules but a normal scan does not exclude the diagnosis. The main causes of FB are collagen vascular diseases (especially rheumatoid arthritis) and immunodeficiency syndromes. The treatment of FB is not well defined.