Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Bronchiolitis obliterans ?
    ### Response:
    Bronchiolitis obliterans is an inflammatory obstruction of the lung's tiniest airways, the bronchioles. The bronchioles may become damaged and inflamed after inhalation of toxic fumes, as a result of respiratory infections, in association with connective tissue disorders, or after bone marrow or heart-lung transplants.
    