Hello and welcome to the forum. Thanks for your question. Are you asking for yourself or your child? Lymphocytic bronchiolitis is a lung infection (inflammation of the bronchioles-the airways that extend beyond the bronchi and end in the alveoli) that affects the more distal airways; it is a viral inflammatory process. Most people are diagnosed with this in childhood but has been seen in older people as well. In the adult clinic, conventional and high-resolution radiology and respiratory functional studies are suggestive of the diagnosis but the etiology usually requires tissue. https://www.mayoclinic.org/diseases-conditions/bronchiolitis/diagnosis-treatment/drc-20351571 So, the imaging is imperative and likely a gas exchange test but perhaps not a biopsy. Please give us more details and let us know how you are doing.